Nomenclature of Organic Chemistry. IUPAC Recommendations and Preferred Names 2013.

P-60 Introduction
P-61 Substitutive nomenclature: prefix mode
P-62 Amines and imines
P-63 Hydroxy compounds, ethers, peroxols, peroxides and chalcogen analogues
P-64 Ketones, pseudoketones and heterones, and chalcogen analogues
P-65 Acids and derivatives
P-66 Amides, hydrazides, nitriles, aldehydes
P-67 Oxoacids used as parents for organic compounds
P-68 Nomenclature of other classes of compounds
P-69 Organometallic compounds

P-66.0 Introduction
P-66.1 Amides
P-66.2 Imides
P-66.3 Hydrazides
P-66.4 Amidines, amidrazones, hydrazidines, and amidoximes (amide oximes)
P-66.5 Nitriles
P-66.6 Aldehydes

The classes dealt with in this Section have in common the fact that their retained names are derived from those of acids by changing the ‘ic acid’ ending to a class name, for example ‘amide’, ‘ohydrazide’, ‘nitrile’, or ‘aldehyde’. Their systematic names are formed substitutively by the suffix mode using one of two types of suffix, one that includes the carbon atom, for example, ‘carbonitrile’ for –CN, and one that does not, for example, ‘-nitrile’ for –(C)N. Amidines are named as amides, hydrazidines as hydrazides, and amidrazones as amides or hydrazides.

P-66.1 AMIDES

P-66.1.0 Introduction
P-66.1.1 Primary amides
P-66.1.2 Secondary and tertiary amides
P-66.1.3 ‘Hidden’ amides
P-66.1.4 Chalcogen analogues of amides
P-66.1.5 Lactams, lactims, sultams, and sultims
P-66.1.6 Amides derived from carbonic, cyanic, and the di- and polycarbonic acids
P-66.1.7 Polyfunctional amides

Amides are derivatives of organic oxoacids in which each hydroxy group has been replaced by an amino or substituted amino group. Chalcogen replacement analogues are called thio-, seleno-, and telluroamides. Compounds having one, two, or three acyl groups on a single nitrogen atom are generically included.

P-66.1.1 Primary amides

P-66.1.1.1 Carboxamides
P-66.1.1.2 Sulfonamides, sulfinamides, and related selenium and tellurium amides
P-66.1.1.3 Substitution of primary amides
P-66.1.1.4 Amides denoted as prefixes

Names of carboxamides are formed in two ways:

P-66.1.1.1.1 Substitutive nomenclature
P-66.1.1.1.2 Modification of retained names for acids

P-66.1.1.1.1.1 Alicyclic mono- and diamides are named substitutively by adding the suffix ‘amide’, to the appropriate parent hydride name, with elision of the final letter ‘e’ before ‘a’. The multiplying prefix ‘di’ is used to name diamides.

Examples:

Example:

propane-1,2,3-tricarboxamide (PIN)

Examples:

Names of amides derived from carboxylic acids listed in P-65.1.1 are formed by changing the ‘ic acid’ or ‘-oic acid’ ending of the retained names of carboxylic acids into ‘amide’. Names of amides formed by this method are either preferred IUPAC names or names for use in general nomenclature according to the status of the corresponding acid; structures can be substituted in the same way as indicated for the corresponding acids (see P-65.1.1).

P-66.1.1.1.2.1 Only the following four retained names are preferred IUPAC names and can be substituted. The name ‘oxamide’ is a contracted name from ‘oxalamide’ and substitution on the nitrogen atoms is allowed.

Examples:

Examples:

benzene-1,2-dicarboxamide (PIN)
phthalamide

benzene-1,4-dicarboxamide (PIN)
terephthalamide

Examples:

prop-2-enamide (PIN)
acrylamide

N-methylprop-2-enamide (PIN)
(not N-methylacrylamide;
substitution is not allowed on acrylamide)

2-hydroxypropanamide (PIN)
lactamide

2-hydroxy-N-methylpropanamide (PIN)
(not N-methyllactamide)

Examples:

R = –CO-NH₂
methyl β-D-galactopyranosiduronamide

2-aminoacetamide
glycinamide

–SO2-NH2		sulfonamide (preselected suffix)
–SO-NH2		sulfinamide (preselected suffix)
–SeO2-NH2		selenonamide (preselected suffix)
–SeO-NH2		seleninamide (preselected suffix)
–TeO2-NH2		telluronamide (preselected suffix)
–TeO-NH2		tellurinamide (preselected suffix)

Examples:

P-66.1.1.3.1 N-Substitution
P-66.1.1.3.2 Hydroxamic acids
P-66.1.1.3.3 Amic acids
P-66.1.1.3.4 Anilides
P-66.1.1.3.5 General substitution of amides

P-66.1.1.3.1.1 Substituted primary amides, with general structures such as R-CO-NHR′ and R-CO-NR′R′′, and the corresponding amides derived from chalcogen acids are named by citing the substituents R′ and R′′ as prefixes preceded by the locant N when one amide group is present. In di- and polyamides, except for geminal diamides, N locants with superscripted arabic numbers, which are the locants of the parent structure, are used to differentiate the nitrogen atoms, for example, N¹, N³, etc. (see also P-62.2.4.1.2). The recommended N locants for geminal diamides are discussed in P-66.1.1.3.1.2.

Superscript arabic numbers are now used to differentiate the nitrogen atoms of diamides, where primes (′), double primes (′′), triple primes (′′′), etc. were formerly used.

N-Substitution of primary amides is not allowed when amides having retained names are designated as not substitutable.

Examples:

dimethylformamide (PIN)

N-(propan-2-yl)acetamide (PIN)

N,N-dimethylpropanamide (PIN)
(not N,N-dimethylpropionamide;
substitution is not allowed on propionamide)

N-methylbenzamide (PIN)

N,N-diethylfuran-2-carboxamide (PIN)
N,N-diethyl-2-furamide

N¹-methylbutanediamide (PIN)

N¹,N⁵-dimethylpentanediamide (PIN)

N³-ethyl-N¹-methylnaphthalene-1,3-disulfonamide (PIN)

When geminal carboxamide groups are present, the locants N, N′, etc. are used in association with the numerical locant indicating the position of the groups on a chain or ring. Lowest locants are assigned to the most substituted group; when there is a choice, lowest locants are assigned to the first cited N-substituent.

Examples:

N′¹-ethyl-N¹,N¹,N³-trimethylpropane-1,1,3-tricarboxamide (PIN)

N¹-ethyl-N′¹,N³-dimethylpropane-1,1,3-tricarboxamide (PIN)

Hydroxamic acids have the generic structure R-CO-NH-OH and are named as N-hydroxy amides (see P-65.1.3.4). The suffixes ‘hydroxamic acid’ and ‘carbohydroxamic acid’ but may be used in general nomenclature.

Examples:

Amic acids are derivatives of dicarboxylic acids having a retained name and when one carboxylic group has been changed to a carboxamide group. Preferred IUPAC names for amic acids are generated by method (1) in P-66.1.1.4.1.1. They may also be named by methods (2) and (3) and by replacing the ‘ic acid’ ending in the retained name by ‘amic acid’ (see P-65.1.6.1).

Examples:

(1) 10-amino-10-oxodecanoic acid (PIN)
(2) 9-carbamoylnonanoic acid
(3) 9-(aminocarbonyl)nonanoic acid

(1) 3-amino-3-oxopropanoic acid (PIN)
(2) carbamoylacetic acid
(3) (aminocarbonyl)acetic acid
malonamic acid (see P-65.1.6.1)

N-Phenyl derivatives of primary amides are called ‘anilides’ and may be named using the term ‘anilide’ in place of ‘amide’ in systematic or retained names of amides. The locants for substituents in the N-phenyl ring of anilides are primed numbers. However, names expressing N-substitution by a phenyl group on an amide are preferred IUPAC names.

Examples:

Substitution of amides is expressed by prefixes; numerical, N, and N′ locants are used as required. N-Substitution of amides follows the substitution rules for carboxylic acids described in P-65.1.2.4.

Examples:

3-chloropropanamide (PIN)
(not 3-chloropropionamide;
no substitution on propionamide)

4-chloro-N,N-dimethylbutanamide (PIN)
(not 4-chloro-N,N-dimethylbutyramide;
no substitution on butyramide)

4-(pyridin-4-yl)benzamide (PIN)
4-(4-pyridyl)benzamide

2-chloropyridine-3-carboxamide (PIN)
(not 2-chloronicotinamide)

4-methylbenzene-1,2-dicarboxamide (PIN)
4-methylphthalamide

2-hydroxybenzamide (PIN)
(not salicylamide)

3,5-diamino-6-chloropyrazine-2-carboxamide (PIN)

2,2′-[ethane-1,2-diylbis(azanediyl)]di(cyclohexane-1-carboxamide) (PIN)

Two different substituent groups can be derived from amides and expressed as prefixes in the presence of a characteristic group having seniority for citation as suffix:

P-66.1.1.4.1 Substituents of the types –CO-NH₂ and –CO-CO-NH₂
P-66.1.1.4.2 Substituents of the types –SO₂-NH₂ , –SO-NH₂ and their selenium and tellurium analogues
P-66.1.1.4.3 Substituents of the types –NH-CO-R and –NH-SO₂-R
P-66.1.1.4.4 Substituent groups R-CO-N< and R-CO-N=, or R-SO₂-N< and R-SO₂-N= (and selenium and tellurium analogues)
P-66.1.1.4.5 Substituent groups derived from oxamide, H₂N-CO-CO-NH₂

P-66.1.1.4.1.1 In the presence of a characteristic group having priority for citation as suffix or if all carbamoyl groups cannot be included in the suffix, the –CO-NH₂ group is named in three different ways:

(1) by using the two prefixes ‘amino’ and ‘oxo’ to denote such groups on terminal atoms of carbon chains having more than one carbon atom;

(2) by using the acyl group name ‘carbamoyl’ (see P-65.2.1.5);

(3) by using the prefix ‘aminocarbonyl’.

Examples:

(2) 3-(dimethylcarbamoyl)pentanedioic acid (PIN)
(3) 3-[(dimethylamino)carbonyl]pentanedioic acid

(1) 5-(2-amino-2-oxoethyl)furan-2-carboxylic acid (PIN)
(2) 5-(carbamoylmethyl)furan-2-carboxylic acid
(3) 5-[(aminocarbonyl)methyl]furan-2-carboxylic acid

(2) 3-carbamoylnaphthalene-2-carboxylic acid (PIN)
3-carbamoyl-2-naphthoic acid
(3) 3-(aminocarbonyl)naphthalene-2-carboxylic acid
3-(aminocarbonyl)-2-naphthoic acid

(2) 2-carbamoylbenzoic acid (PIN)
(3) 2-(aminocarbonyl)benzoic acid
phthalamic acid (see P-65.1.6.1)

(2) 6-carbamoylnaphthalene-2-sulfonic acid (PIN)
(3) 6-(aminocarbonyl)naphthalene-2-sulfonic acid

(2) 5-methyl-2-[methyl(phenyl)carbamoyl]benzoic acid (PIN)
(3) 5-methyl-2-[(N-methylanilino)carbonyl]benzoic acid
5-methyl-2-{[methyl(phenyl)amino]carbonyl}benzoic acid

Examples:

(1) 4-amino-3,4-dioxobutanoic acid (PIN)
(2) oxamoylacetic acid
(3) (aminooxalyl)acetic acid

(2) 2-oxamoylpyridine-3-carboxylic acid (PIN)
(3) 2-(aminooxalyl)pyridine-3-carboxylic acid

In the presence of a characteristic group having priority for citation as suffix, the groups –SO₂-NH₂, –SO-NH₂ and related selenium and tellurium groups are named in two ways corresponding to methods (2) and (3) for the –CO-NH₂ group above in P-66.1.1.4.1:

(2) by using the acyl group ‘sulfamoyl’ (for sulfonamides only) (see P-65.3.2.3);

(3) by using the prefixes ‘amino...sulfonyl’, ‘amino...sulfinyl’, ‘amino...selenonyl’, ‘amino...seleninyl’, ‘amino...telluronyl’, or ‘amino...tellurinyl’.

Examples:

(2) 2-(dimethylsulfamoyl)benzene-1-sulfonic acid (PIN)
(3) 2-[(dimethylamino)sulfonyl]benzene-1-sulfonic acid

methyl 3-(phenylsulfamoyl)propanoate (PIN)
(3) methyl 3-[(phenylamino)sulfonyl]propanoate
methyl 3-(anilinosulfonyl)propanoate

(3) 6-[(methylamino)sulfinyl]naphthalene-2-carboxylic acid (PIN)
(3) 6-[(methylamino)sulfinyl]-2-naphthoic acid,

When a group having preference for citation as a principal characteristic group is present, the group R-CO-NH–, or R-SO₂-NH– (and selenium and tellurium analogues) of an N-substituted amide is named in two ways:

(1) substitutively, by using a prefix formed by changing the final letter ‘e’ in the complete name of the amide to ‘o’, thus changing the suffixes ‘amide’ and ‘carboxamide’ into ‘amido’ and ‘carboxamido’, respectively, ‘diamide’ to ‘diamido’ or ‘sulfonamide’ to ‘sulfonamido’, etc.;

(2) substitutively, by using ‘acylamino’ prefixes formed by substituting the substituent group ‘amino’ with the name of the acyl group.

Examples:

(1) 4-formamidobenzoic acid (PIN)
(2) 4-(formylamino)benzoic acid

(1) (4-acetamido-3-methylphenyl)arsonic acid (PIN)
(2) [4-(acetylamino)-3-methylphenyl]arsonic acid

(1) 4-benzamidobenzene-1-sulfonic acid (PIN)
(2) 4-(benzoylamino)benzene-1-sulfonic acid

(1) 3-(methanesulfonamido)propanoic acid (PIN)
(2) 3-[(methanesulfonyl)amino]propanoic acid

N-(cyclohexylmethanesulfonyl)glycine
(1) (1-cyclohexylmethanesulfonamido)acetic acid
(2) {[(cyclohexylmethyl)sulfonyl]amino}acetic acid

N-cyclopropyl-N-(methanesulfonyl)glycine
(1) (N-cyclopropylmethanesulfonamido)acetic acid
(2) [(cyclopropyl(methanesulfoyl)amino]acetic acid

(1) 2-(4-aminobenzene-1-sulfonamido)-1,3-thiazole-5-carboxylic acid (PIN)
(not 2-sulfanilamidothiazole-5-carboxylic acid;
sulfanilic acid is not a retained name)
(2) 2-{[(4-aminophenyl)sulfonyl]amino}-1,3-thiazole-5-carboxylic acid

(1) 2-(N-methylpropanamido)benzene-1-sulfonic acid (PIN)
(2) 2-[methyl(propanoyl)amino]benzene-1-sulfonic acid

(1) 4,4′-butanediamidodibenzoic acid (PIN)
(2) 4,4′-[butanedioylbis(azanediyl)]dibenzoic acid
4,4′-[1,4-dioxobutane-1,4-diylbis(azanediyl)]dibenzoic acid

N-methyl-N-(quinolin-4-yl)acetamide (PIN)
(not 4-(N-methylacetamido)quinoline)
{not 4-[acetyl(methyl)amino]quinoline}

N-(dibenzo[b,d]furan-1-yl)acetamide (PIN)
(not 1-acetamidodibenzofuran)
[not 1-(acetylamino)dibenzofuran]

When an amide is the principal function, it must be named as such. The method of considering amides as substituents on polycyclic ring systems, described in the 1993 Recommendations (ref. 2), should be avoided, even in general nomenclature (see also P-66.1.3).

P-66.1.1.4.4 Substituent groups R-CO-N< and R-CO-N= , or R-SO₂-N< and R-SO₂-N= (and selenium and tellurium analogues)

When a group having preference for citation as a principal characteristic group is present, the groups R-CO-N< and R-CO-N=, or R-SO₂-N< and R-SO₂-N= (and selenium and tellurium analogues) of an N-substituted amide are named by combining acyl group names with those of the appropriate nitrogen substituent groups, azanediyl and imino, respectively.

Examples:

4,4′-(acetylazanediyl)dibenzoic acid (PIN)

methyl 4-[(methanesulfonyl)imino]cyclohexane-1-carboxylate (PIN)

P-66.1.1.4.5.1 Prefixes for the group H₂N-CO-CO-NH– are ‘oxamoylamino’ (preferred prefix) or ‘amino(oxo)acetamido’. The preferred prefix for the group H₂N-CO-CO-N= is ‘oxamoylimino’.

Example:

Concatenated preferred prefixes for the groups –HN-CO-CO-NH–, >N-CO-CO-N<, and =N-CO-CO-N= are ‘oxalylbis(azanediyl)’, ‘oxalyldinitrilo’, and ‘oxalylbis(azanylylidene)’, respectively. The preferred prefix for the group H₂N-CO-CO-N< is ‘oxamoylazanediylְ.

Example:

Amides having general formulas (R-CO)₂NH, (R-SO₂)₂NH, etc., and (R-CO)₃N, (R-SO₂)₃N, etc., respectively, are named as N-acyl derivatives of the senior primary amide or preferred prefix. Names based on the substitution of the parent hydride ‘azane’ or the pseudo parent hydride ‘amine’ by acyl groups, for example, diacetylazane or diacetylamine, as recommended in the 1993 Recommendations (ref. 2) are not included in these recommendations, nor are trivial names such as diacetamide, triacetamide, dibenzamide, and tribenzamide.

Examples:

An N-acyl group attached to a nitrogen atom of a heterocyclic system has been called a ‘hidden amide’, i.e., an amide that cannot be named as such by accepted substitutive principles. The traditional way to name such compounds by using acyl groups as substituents on the nitrogen atom of the heterocyclic system is allowed but only in general nomenclature. Such compounds are now considered as pseudoketones (see P-64.3) and preferred IUPAC names are constructed accordingly.

An N-acyl group attached to a nitrogen atom of a heterocyclic system is now preferably named as a pseudoketone (see P-64.1.2.1, P-64.3) and not as an acyl substituent on the nitrogen as in previous recommendations; the latter method can be used in general nomenclature.

Examples:

1-(piperidin-1-yl)ethan-1-one (PIN)
1-acetylpiperidine

1-(3,4-dihydroquinolin-1(2H)-yl)propan-1-one (PIN)
1-propanoyl-1,2,3,4-tetrahydroquinoline
1-propionyl-1,2,3,4-tetrahydroquinoline

Chalcogen analogues of amides are named systematically. Prefixes, such as ‘thio’, modifying retained names are no longer recommended for preferred names.

P-66.1.4.1 Names of chalcogen analogues of primary amides

P-66.1.4.1.1 Names are formed by using suffixes modified by functional replacement nomenclature using prefixes and infixes.

Examples:

Examples:

Names are formed by the addition of appropriate prefixes to names described in P-65.1.7.2.3

Examples:

Names are formed as described in P-64.6.1 for chalcogen derivatives of pseudoketones.

Example:

1-(pyrrolidin-1-yl)ethane-1-thione (PIN)
[not 1-(ethanethioyl)pyrrolidine]

(1) by a prefix formed by changing the final letter ‘e’ in the name of the amide into ‘o’;

(2) by the appropriate prefixes, such as amino, in conjunction with sulfanylidene or thioxo, as well as carbonothioyl (not thiocarbonyl) for –CS– or carbamothioyl (not thiocarbamoyl) for –CS-NH₂.

3-amino-3-sulfanylidenepropanoic acid (PIN)
3-amino-3-thioxopropanoic acid
carbamothioylacetic acid
(aminocarbonothioyl)acetic acid

4-(ethanethioamido)benzamide (PIN)
4-[(ethanethioyl)amino]benzamide
4-(thioacetamido)benzamide

CH₃-S(S)-NH-CH₂-COOH
[(methanesulfinothioyl)amino]acetic acid (PIN)

2-[amino(sulfanylidene)ethanethioyl]benzoic acid (PIN)

P-66.1.5.1 Lactams and lactims

Intramolecular amides of amino carboxylic acids, –CO-NH–, are called ‘lactams’ and their tautomers, –C(OH)=N–, are ‘lactims’. Lactams are named in two ways:

(1) as heterocyclic pseudoketones;

(2) by substituting ‘lactam’ for the ‘ic acid’ ending of a systematic ‘oic acid’ name for the parent acid without the amino substituent, and inserting a locant designating the position of the amino group between the ‘o’ and ‘lactam’. Lactims are named in the same way, using ‘lactim’ in place of ‘lactam’.

Examples:

pyrrolidin-2-one (PIN)
butano-4-lactam

1-azacyclotridecan-2-one (PIN)
dodecano-12-lactam

3,4,5,6-tetrahydropyridin-2-ol (PIN)
pentano-5-lactim

3,4,5,6,7,8-hexahydroazocin-2-ol (PIN)
1,2-didehydroazocan-2-ol
heptano-7-lactim

P-66.1.5.2.1 Intramolecular amides of amino sulfonic acids are called ‘sultams’ and may be named in three ways

(1) as heterocyclic heterones;

(2) by citing the term ‘sultam’ denoting the cyclic –NH-SO₂– group after the name of the appropriate parent hydride preceded by a pair of locants describing the points of attachment of the sulfonyl group and the nitrogen atom, respectively; the locant of the sulfonyl group is cited first, and, if there is a choice, is the lower locant. Multiplying prefixes and pairs of locants separated by a colon are used to indicate two or more sultam rings;

(3) as heterocycles and, according to functional class nomenclature, using the class term ‘oxide’.

Examples:

(1) 1λ⁶-naphtho[1,8-cd][1,2]thiazole-1,1(2H)-dione (PIN)
(3) 2H-naphtho[1,8-cd][1,2]thiazole 1,1-dioxide
(2) naphthalene-1,8-sultam

(1) 1λ⁶,2-thiazinane-1,1-dione (PIN)
(3) 1,2-thiazinane 1,1-dioxide
(2) butane-1,4-sultam

Examples:

(1) 1-hydroxy-4,5-dihydro-3H-1λ⁶,2-thiazol-1-one (PIN)
(3) 1-hydroxy-4,5-dihydro-3H-1λ⁴,2-thiazole 1-oxide
(2) propane-1,3-sultim

(1) 1-hydroxy-1λ⁶-thia-2-azacyclododec-1-en-1-one (PIN)
(3) 1-hydroxy-1λ⁴-thia-2-azacyclododec-1-ene 1-oxide
(2) decane-1,10-sultim

Cyclic amides of amino sulfinic acids and their tautomers are named as heterocyclic compounds.

Examples:

1λ⁴,2-thiazinan-1-one (PIN)
1,2-thiazinane 1-oxide

3,4,5,6-tetrahydro-1λ⁴,2-thiazin-1-ol (PIN)

P-66.1.6.1 Amides derived from carbonic acid and related compounds

P-66.1.6.1.1 Urea and its substitutive derivatives
P-66.1.6.1.2 Isourea and its derivatives
P-66.1.6.1.3 Chalcogen analogues of urea and isourea
P-66.1.6.1.4 Condensed ureas

P-66.1.6.1.1.1 The compound H₂N-CO-NH₂ has the retained name ‘urea’, which is the preferred IUPAC name, with locants N and N′, as shown above the structure below. The systematic name is ‘carbonic diamide’. The locants 1, 2, and 3 have been used in the past and may be used in general nomenclature.

urea (PIN)

carbonic diamide

Numerical locants for urea are no longer used in the IUPAC preferred name.

P-66.1.6.1.1.2 Derivatives of urea formed by substitution on the nitrogen atom(s) are named as substitution products in accordance with the seniority order of urea that is ranked as an amide of carbonic acid. Amides of cyanic and the di- and polycarbonic acids follow the same seniority as the corresponding acid (see P-42.2).

Examples:

N,N′-dimethylurea (PIN)
N,N′-dimethylcarbonic diamide

N-(propan-2-ylidene)urea (PIN)
isopropylideneurea
N-(propan-2-ylidene)carbonic diamide

N-[1-cyano-3-(methylsulfanyl)propyl]-N′-methylurea (PIN)
N-[1-cyano-3-(methylsulfanyl)propyl]-N′-methylcarbonic diamide

The prefixes ‘ureido’ and ‘ureylene’ are no longer acceptable in IUPAC nomenclature. The prefixes ‘carbamoylamino’ and ‘carbonylbis(azanediyl)’, respectively are recommended for preferred IUPAC names.

2-[(methylcarbamoyl)amino]naphthalene-1-carboxylic acid (PIN)
2-{[(methylamino)carbonyl]amino}-1-naphthoic acid
[not 2-(3-methylureido)naphthalene-1-carboxylic acid]

7,7′-[carbonylbis(azanediyl)]di(naphthalene-2-sulfonic acid) (PIN)
[not 7,7′-ureylenedi(naphthalene-2-sulfonic acid)]

N-carbamoylbenzamide (PIN)
N-(aminocarbonyl)benzamide

N-carbamoylbenzenesulfonamide (PIN)
N-(aminocarbonyl)benzenesulfonamide

N-carbamoyl-2-phenylacetamide (PIN)
N-(aminocarbonyl)-2-phenylacetamide

Two carboxylic acids are related to urea; have been known as ‘allophanic acid’ for H₂N-CO-NH-COOH and ‘hydantoic acid’ for H₂N-CO-NH-CH₂-COOH. These names are no longer recommended. Preferred IUPAC names for these two acids and their derivatives are formed systematically.

Examples:

Amides are ranked in the same way as the corresponding acids (see P-42). Thus, in substitutive nomenclature, amides from carboxylic acids, including formamide, are senior to urea.

Examples:

N-[2-(carbamoylamino)ethyl]acetamide (PIN)
N-{2-[(aminocarbonyl)amino]ethyl}acetamide

H₂N-CO-NH-CH₂-CH₂-CH₂-NH-CHO
N-[3-(carbamoylamino)propyl]formamide (PIN)
[not N-(3-formamidopropyl)urea
nor N-[3-(formylamino)propyl]urea;
formamide is preferred to urea, see P-41]

P-66.1.6.1.2.1 The imidic acid tautomer of urea, H₂N-C(OH)=NH, is named ‘carbamimidic acid’, a shortened form of the systematic functional replacement name ‘carbonamidimidic acid’. The name ‘isourea’ is no longer recommended, but is retained as a class name. In preferred IUPAC names, derivatives of carbamimidic acid are named using the locants N and N′. Since the name isourea is no longer recommended, even for general nomenclature, no numerical locants used in previous recommendations are needed. When the position of the double bond is unknown, only the locant N is used.

carbamimidic acid (PIN)
(not isourea)

ethyl N′-methyl-N,N-diphenylcarbamimidate(PIN)
(not O-ethyl-N′-methyl-N,N-diphenylisourea)

ethyl N,N-diphenylcarbamimidate (PIN)
(not O-ethyl-N,N-diphenylisourea)

ethyl N-phenylcarbamimidate (PIN)
(not O-ethyl-N-phenylisourea)

The prefixes 1-isoureido and 3-isoureido are no longer recommended.

Example:

7-{[(dimethylamino)ethoxymethylidene]amino}naphthalene-2-carboxylic acid (PIN)
[not 7-(2-ethyl-1,1-dimethyl-3-isoureido)naphthalene-2-carboxylic acid]

P-66.1.6.1.3.1 Chalcogen analogues of urea are named by functional replacement nomenclature using the prefixes ‘thio’, ‘seleno’, and ‘telluro’. Preferred IUPAC names use the letter locants N, and N′. Numerical locants may be used for thiourea in general nomenclature.

carbonothioic diamide

thiourea (PIN)

Numerical locants are no longer used for thiourea in the IUPAC preferred name.

Example:

N-(butan-2-yl)selenourea (PIN)
N-(1-methylpropyl)selenourea
N-(butan-2-yl)carbonoselenoic diamide

carbamimidothioic acid (PIN)
(not isothiourea)

ethyl N,N-dimethylcarbamimidothioate (PIN)
(not S-ethyl-N,N-dimethylisothiourea)

ethyl N′-methylcarbamimidothioate (PIN)
(not S-ethyl-N′-methylisothiourea)

3-(carbamothioylamino)propanoic acid (PIN)
3-{[amino(sulfanylidene)methyl]amino}propanoic acid

Condensed ureas, H₂N-[CO-NH]_n-H, where n = 2, 3, or 4, are named systematically as diamides of imidodicarbonic acid, diimidotricarbonic acid, and triimidotetracarbonic acid, etc., functional replacement names derived from the corresponding di- or polycarbonic acids. The names biuret, triuret, etc., are no longer recommended as preferred IUPAC names. Chalcogen analogues are described by functional replacement prefixes alphabetized along with ‘imido’ in front of the corresponding di- or polycarbonic acid. Locants, as shown above the structures, below, are used to indicate the positions of substituents and functional replacement prefixes, where needed. Preferred IUPAC names use these locants which are also prescribed for the amides of imidopolycarbonic acids (see P-66.4.1.2.2). The full numerical numbering system used previously and shown below the structures may be used in general nomenclature.

2-imidodicarbonic diamide (PIN)
biuret

2,4-diimidotricarbonic diamide (PIN)
triuret

Numerical locants for condensed ureas are no longer used in IUPAC preferred names.

Examples:

N¹-methyl-2-imidodicarbonic diamide (PIN)
1-methylbiuret

N¹-methyl-2-imido-1-thiodicarbonic diamide (PIN)
1-methyl-2-thiobiuret

N¹-methyl-2,4-diimido-3-thiotricarbonic diamide (PIN)
1-methyl-4-thiotriuret

Example:

3,5,7-trioxo-2,4,6,8-tetraazanonane-1,9-diamide (PIN)
pentauret

The traditional name ‘cyanamide’ is retained for NC-NH₂ and is the preferred IUPAC name. Substitution is allowed on the –NH₂ group. The systematic functional replacement name is carbononitridic amide.

Examples:

Systematic names for amides of the polycarbonic acids are formed by adding the functional class name ‘amide’ to that of the corresponding acid, preceded by the numerical prefix ‘di’ to indicate the presence of two –NH₂ groups. Chalcogen analogues are described by functional replacement prefixes. Numerical and letter locants are used to number the structures.

dicarbonic diamide (PIN)

tricarbonic diamide (PIN)

N¹-(propan-2-yl)dicarbonic diamide (PIN)
N-isopropyldicarbonic diamide

N¹-methyl-2-thiotricarbonic diamide (PIN)

1,2,3-trithiodicarbonic diamide (PIN)
(not ‘thiuram monosulfide’)

2-dithioperoxy-1,3-dithiodicarbonic diamide (PIN)
(not ‘thiuram disulfide’)

Amides follow acids, anhydrides, esters, and acid halides in the seniority order of compound classes expressed by suffixes (see P-41); within the amide class, amides rank in the same order as the corresponding acid. Seniority for numbering polyfunctional amides follows that described for acids, for which see P-65.1.2.3 and P-65.1.2.4.

Examples:

1-(dinitromethyl)hydrazine-1,2-dicarboxamide (PIN)

N-[({[(acetamidomethyl)nitramido]methyl}nitramido)methyl]prop-2-enamide (PIN)
N-{[{[(acetamidomethyl)(nitro)amino]methyl}(nitro)amino]methyl}prop-2-enamide
N-{[({[(acetylamino)methyl](nitro)amino}methyl)(nitro)amino]methyl}prop-2-enamide

2-(1-aminopropan-2-ylidene)hydrazine-1-carboxamide (PIN)

4-[(2-hydroxyethyl)amino]-N-{2-[(2-hydroxyethyl)amino]ethyl}butanamide (PIN)

2-amino-N-(2,3-dihydroxypropyl)-N-methylacetamide (PIN)

P-66.2.1 Imides are compounds containing the structural grouping –CO-NH-CO–. Acyclic imides are N-acyl derivatives of primary amides and are named as such (see P-66.1.2.1). Cyclic imides are preferably named as heterocyclic pseudoketones. They may also be named by replacing the suffixes ‘dioic acid’, or ‘dicarboxylic acid’ of the corresponding dibasic acid, or ‘ic acid’ in retained names of diacids, by ‘imide’ or ‘dicarboximide’.

Examples:

pyrrolidine-2,5-dione (PIN)
succinimide

1H-pyrrole-2,5-dione (PIN)
pyrrole-2,5-dione

1-bromopyrrolidine-2,5-dione (PIN)
(not N-bromosuccinimide;
substitution is not allowed on succinimide)

hexahydro-1H-isoindole-1,3(2H)-dione (PIN)
hexahydro-2H-isoindole-1,3-dione
cyclohexane-1,2-dicarboximide

2-phenyl-1H-isoindole-1,3(2H)-dione (PIN)
2-phenyl-2H-isoindole-1,3-dione
N-phenylphthalimide

1,3-oxazetidine-2,4-dione (PIN)

succinimido
2,5-dioxopyrrolidin-1-yl (preferred prefix)

7-phthalimido-1-naphthoic acid
7-(1,3-dioxo-1,3-dihydro-2H-isoindol-2-yl)naphthalene-1-carboxylic acid (PIN)

P-66.3.0 Definition
P-66.3.1 Systematic names
P-66.3.2 Substituent groups derived from hydrazides
P-66.3.3 Substituted hydrazides
P-66.3.4 Chalogen analogues of hydrazides
P-66.3.5 Hydrazides from carbonic, cyanic, and di- and polycarbonic acids
P-66.3.6 Semioxamazones

Hydrazides are compounds derived from the organic oxoacids denoted by a suffix, such as –COOH, –SO₂-OH, –SO-OH, etc., by replacing –OH groups with –NH-NH₂ groups.

P-66.3.1 Systematic names

Hydrazides of the type R-CO-NH-NH₂ are named in two ways:

(1) by substitutive nomenclature;

(2) by modification of retained names of carboxylic acids.

Hydrazides are named substitutively by using the following suffixes (see Table 4.4). The method of naming hydrazides as acyl derivatives of hydrazine is no longer recommended.

For naming acyclic hydrazides, the suffix ‘hydrazide’ is recommended in place of ‘ohydrazide’ in accordance with the general use of suffixes added to names of parent hydrides, for example pentanehydrazide for CH3-CH2-CH2-CH2-CO-NH-NH2, not pentanohydrazide.

The suffix ‘hydrazide’ is used to name acyclic compounds. The suffix ‘carbohydrazide’ is used to denote the –CO-NH-NH₂ characteristic group attached to cyclic compounds and in chains having more than two –CO-NH-NH₂ characteristic groups, or when the group is attached to a heteroatom of a heterocycle or parent compound. Multiplicative nomenclature may be used when the symmetry conditions for its use are met.

Nitrogen atoms in hydrazides are identified by the locants N and N′ as , even though hydrazine itself, is numbered using the numerical locants 1 and 2, . When two hydrazide suffixes are attached to an acyclic alkane, the suffix in position 1 is labeled N¹, N′¹, a second suffix in position ‘x’, N^x, N′^x (see P-16.9).

Examples:

pentanehydrazide (PIN)
(not pentanoylhydrazine)

butanedihydrazide (PIN)
succinohydrazide (see P-66.3.1.2)
[not (ethane-1,2-diyldicarbonyl)dihydrazine]
[not succinyldihydrazine]

cyclohexanecarbohydrazide (PIN)
[not (cyclohexanecarbonyl)hydrazine]

piperidine-1-carbohydrazide (PIN)
[not (piperidine-1-carbonyl)hydrazine]

methanesulfonohydrazide (PIN)
[not (methanesulfonyl)hydrazine]

ethane-1,1,1-tricarbohydrazide (PIN)

Names of hydrazides are formed by changing the ‘ic acid’ or ‘-oic acid’ ending of the retained names of carboxylic acids into ‘ohydrazide’ (for nitrogen locants, see P-66.3.3).

P-66.3.1.2.1 Only the following five names are preferred IUPAC names and can be substituted in the same way as corresponding amides (see P-66.1.1.1.2). Systematic substitutive names are used to generate acids modified by functional replacement.

cyanohydrazide (PIN)
hydrazinecarbonitrile (see P-66.5.1.1.3)

formohydrazide (PIN)
(not hydrazinecarbaldehyde; see P-66.6.1.3)

acetohydrazide (PIN)

benzohydrazide (PIN)

oxalohydrazide (PIN)

Example:

Examples:

benzene-1,2-dicarbohydrazide (PIN)
phthalohydrazide

benzene-1,4-dicarbohydrazide (PIN)
terephthalohydrazide

Example:

butanehydrazide (PIN)
butyrohydrazide
(substitution not allowed)

Examples:

D-gluconohydrazide

2-aminoacetohydrazide
glycinohydrazide

Substituent groups corresponding to hydrazides are of two types: –CO-NH-NH₂ , –SO₂-NH-NH₂, etc.; and –NH-NH-CO-R , –NH-NH-SO₂-R , etc.

P-66.3.2.1 Substituent groups of the type –CO-NH-NH₂, –SO₂-NH-NH₂, etc., may be named in three ways except when the –CO-NH-NH₂ group is at the end of a carbon chain:

(1) as an acyl group derived from the corresponding acid, which gives the preferred prefix; or

(2) as the appropriate carbonohydrazidoyl acyl prefix; or

(3) by concatenation using the prefix hydrazinyl with carbonyl.

hydrazinecarboxylic acid (PIN)
carbonohydrazidic acid

(1) hydrazinecarbonyl (preferred prefix)
(2) carbonohydrazidoyl (see P-65.2.1.4)
(3) hydrazinylcarbonyl

hydrazinesulfonic acid (preselected name)

(1) hydrazinesulfonyl (preselecteded prefix, see P-65.3.2.2.2)
(3) hydrazinylsulfonyl

hydrazinesulfinic acid (preselected name)

(1) hydrazinesulfinyl (preselecteded prefix: see P-65.3.2.2.2)
(3) hydrazinylsulfinyl

Examples:

(hydrazinesulfonyl)acetic acid (PIN)
(hydrazinylsulfonyl)acetic acid

3-(hydrazinesulfinyl)naphthalene-2-carboxylic acid (PIN)
3-(hydrazinylsulfinyl)naphthalene-2-carboxylic acid

2-(hydrazinecarbonyl)benzene-1-sulfonic acid (PIN)
2-carbonohydrazidoylbenzene-1-sulfonic acid

Example:

3-hydrazinyl-3-oxopropanoic acid (PIN)
(hydrazinecarbonyl)acetic acid
carbonohydrazidoylacetic acid

(1) by expressing the corresponding hydrazide as a prefix by replacing the final letter ‘e’ in the name of the hydrazide by the letter ‘o’, for example, ‘acetohydrazido’, ‘propanehydrazido’, and ‘benzohydrazido’; the locant N designates the nitrogen atom adjacent to the –CO– group.

(2) as an acylhydrazinyl substituent group; the hydrazinyl group is numbered by using numerical locants ‘1’ and ‘2’, the locant ‘1’ being the nitrogen atom adjacent to the free valence.

Examples:

(1) 4-acetohydrazidobenzoic acid (PIN)
(2) 4-(2-acetylhydrazin-1-yl)benzoic acid

(1) 4-(N-ethylacetohydrazido)benzene-1-sulfonic acid (PIN)
(2) 4-(2-acetyl-2-ethylhydrazin-1-yl)benzene-1-sulfonic acid

Example:

4-(1-acetyl-2-ethylhydrazin-1-yl)benzoic acid (PIN)

P-66.3.3.1 Alkyl, aryl, cycloalkyl, etc. substituents on the nitrogen atoms of hydrazides are described by the appropriate prefix names and the locants ‘N’ for –NH– and ‘N′’ for –NH₂, as illustrated below. The locants ‘1′’and ‘2′’ have been used in the past for naming hydrazides as derivatives of hydrazine; these locants are no longer recommended. Preferred IUPAC names are hydrazide names and use the locants ‘N’ and ‘N′’

N-methylacetohydrazide (PIN)
(not 1-acetyl-1-methylhydrazine)

2-chloro-N,N′,N′-trimethylpropanehydrazide (PIN)
[not 1-(2-chloropropanoyl)-1,2,2-trimethylhydrazine]

Examples:

N¹,N′⁴-dimethylnaphthalene-1,4-dicarbohydrazide (PIN)
(numbering is based on the lower set of locants:
since N¹ is lower than N′¹; the set N¹,N′⁴ is lower than N′¹,N⁴)

N¹,N′⁴,6-trimethylnaphthalene-1,4-dicarbohydrazide (PIN)
(the numbering is based on the lowest set of locants for the three substituent groups,
and ‘N¹,N′⁴,6’ is lower than ‘N′¹,N⁴,7’)

N′,N′′′-methylenediacetohydrazide (PIN, a multiplicative name)

Examples:

N′-benzoylbenzohydrazide (PIN)
(not 1,2-dibenzoylhydrazine)

N′-acetyl-N′-ethyl-N-methylpropanehydrazide (PIN)
(not 1-acetyl-1-ethyl-2-methyl-2-propanoylhydrazine)

Chalcogen analogues of hydrazides are named substitutively using suffixes formed by functional replacement, i.e., ‘thiohydrazide’, ‘carbothiohydrazide’, ‘sulfonothiohydrazide’, etc., as described in P-33.2.2 and Table 4.4.

The following methods are no longer recommended:

(a) substitution of hydrazine with appropriately modified acyl groups;

(b) modification of retained names by the prefixes ‘thio’, ‘seleno’, ‘telluro’.

propanethiohydrazide (PIN)
[not (propanethioyl)hydrazine;
nor (thiopropionyl)hydrazine]

benzenecarbothiohydrazide (PIN)
[not (benzenecarbothioyl)hydrazine;
nor (thiobenzoyl)hydrazine]

2-hydrazinyl-2-sulfanylideneacetohydrazide (PIN)
(not thiooxalic dihydrazide)

P-66.3.5.1 Preferred IUPAC names for hydrazides derived from carbonic and cyanic acids are chosen according to the seniority order of classes.

Examples:

cyanohydrazide (PIN)
[cyanic acid is a retained name (see P-65.2.2)]
carbononitridic hydrazide
hydrazinecarbonitrile

hydrazinecarboxylic acid (PIN)
carbonohydrazidic acid

hydrazinecarbohydrazide (PIN)
carbonic dihydrazide

Examples:

dicarbonic dihydrazide (PIN)
[(hydrazinecarbonyl)oxy]formohydrazide

2-imidodicarbonic dihydrazide (PIN)
[(hydrazinecarbonyl)amino]formohydrazide

When a group having priority for citation as a principal characteristic group is present, the hydrazide group is named:

(1) as an acylhydrazinyl compound; the hydrazinyl group is numbered by the numerical locants 1 and 2;

(2) by expressing the corresponding hydrazide substitutively as a prefix by replacing the final letter ‘e’ in the name of the hydrazide by the letter ‘o’.

Examples:

3-formohydrazidopropanoic acid (PIN)
3-(2-formylhydrazin-1-yl)propanoic acid

4-{[(hydrazinecarbonyl)oxy]formohydrazido}butanoic acid (PIN)
4-(2-{[(hydrazinecarbonyl)oxy]carbonyl}hydrazin-1-yl)butanoic acid

H₂N-NH-CO-NH-NH-CH₂-COOH
(hydrazinecarbohydrazido)acetic acid (PIN)
[2-(hydrazinecarbonyl)hydrazin-1-yl]acetic acid
[2-(hydrazinylcarbonyl)hydrazin-1-yl]acetic acid

Semioxamazones have the general structure R=N-NH-CO-CO-NH₂. They are derivatives of the hydrazide of oxamic acid. Their preferred IUPAC names are based on the parent name acetamide, but they may also be named as derivatives of oxamic hydrazide.

Example:

P-66.4.1 Amidines
P-66.4.2 Amidrazones
P-66.4.3 Hydrazidines
P-66.4.4 Amidoximes (amide oximes)

Compounds having the general structure R-C(=NH)-NH₂ generically are known as ‘carboxamidines’ and those having the general structure R-S(=NH)-NH₂ as ‘sulfinamidines’. Compounds having the structures below are known only as ‘sulfonimidamides’, and not as amidines.

    or    

P-66.4.1.1 Suffixes for amidines
P-66.4.1.2 Amidines of carbonic, and di- and polycarbonic acids
P-66.4.1.3 Prefixes for the amidine characteristic group
P-66.4.1.4 Substituted amidines
P-66.4.1.5 Formamidine disulfides
P-66.4.1.6 Diamidides

Amidines are named as amides by functional replacement nomenclature in which the =O atom has been replaced by the =NH group. As a principal characteristic group they are designated by the suffixes ‘-imidamide’ and ‘-carboximidamide’. The locant for the –NH₂ group is N and for the imino group N′. The suffixes ‘-amidine’ and ‘-carboxamidine’ are no longer recommended.

-imidamide (preferred suffix)

-carboximidamide (preferred suffix)

-sulfonimidamide (preselected suffix)

-sulfonodiimidamide (preselected suffix)

-sulfinimidamide (preselected suffix)

-seleninimidamide (preselected suffix)

-sulfonimidothioamide (preselected suffix)

Retained names of amidines are formed by replacing the ‘amide’ ending in names of amides by ‘imidamide’, but these are not preferred IUPAC names; preferred IUPAC names are derived systematically. Other than that, the nomenclatural properties of amides are transferred to amidines; thus, names of amidines correspond to preferred names of amides. Amide names that are not substitutable generate nonsubstitutable amidine names.

Examples:

hexanimidamide (PIN)
(no longer hexanamidine)

cyclohexanecarboximidamide (PIN)
(no longer cyclohexanecarboxamidine)

ethanimidamide (PIN)
acetimidamide
(no longer acetamidine)

methanesulfinimidamide (PIN)
(no longer methanesulfinamidine)

methanimidamide (PIN)
formimidamide
(no longer formamidine)

pentanediimidamide (PIN)
(no longer pentanediamidine)

disilane-1,2-dicarboximidamide (PIN)
(no longer disilane-1,2-dicarboxamidine)

butanediimidamide (PIN)
succinimidamide

ethanediimidamide (PIN)
oxalimidamide

benzene-1,2-dicarboximidamide (PIN)
phthalimidamide
(no longer benzene-1,2-dicarboxamidine)

benzene-1,4-dicarboximidamide (PIN)
terephthalimidamide
(no longer benzene-1,4-dicarboxamidine)

N′′¹-ethyl-N¹,N¹-dimethylcyclohexane-1,1-dicarboximidamide (PIN)

P-66.4.1.2.1 Guanidine and its derivatives

P-66.4.1.2.1.1 The preferred IUPAC name for the ‘amidine’ related to carbonic acid, H₂N-C(=NH)-NH₂, is the retained name ‘guanidine’; the locants N, N′ and N′′ are used in preferred IUPAC names. The locants 1, 2, and 3 have been used but are no longer recommended even for general nomenclature.

P-66.4.1.2.1.2 Hydrocarbyl derivatives are named as substituted guanidines. When the position of the double bond is unknown, the preferred IUPAC name uses a minimum number of primes.

Examples:

N,N,N′,N′-tetramethyl-N′′-phenylguanidine (PIN)
N,N,N′,N′-tetramethyl-N′′-phenylcarbonimidic diamide

N,N,N′-trimethylguanidine (PIN)
N,N,N′-trimethylcarbonimidic diamide

    or    
N,N′-dimethylguanidine (PIN)
(not N,N′′-dimethylguanidine)
N,N′-dimethylcarbonimidic diamide

carbamimidoylamino (preferred prefix)
carbamimidamido
[amino(imino)methyl]amino
guanidino

(H₂N)₂C=N–
(diaminomethylidene)amino (preferred prefix)

The names biguanide, triguanide, etc., are no longer recommended. Condensed guanidines, H₂N-[C(=NH)-NH]_n-H where n = 2, 3, or 4 are named systematically as the diamides of imidodicarbonimidic acid, diimidotricarbonimidic acid, and triimidotetracarbonimidic acid. Locants, as shown, are used to indicate the positions of substituents.

imidodicarbonimidic diamide (PIN)

diimidotricarbonimidic diamide (PIN)

N′¹-ethyl-N¹,N¹-diphenylimidodicarbonimidic diamide (PIN)

Example:

3,5,7-triimino-2,4,6,8-tetraazanonane-1,9-diimidamide (PIN)

P-66.4.1.3.1 The systematic name for the group –C(=NH)-NH₂ is ‘carbamimidoyl’; it is the name of the acyl group derived from the name carbamimidic acid, HO-C(=NH)-NH₂ and is the preferred IUPAC prefix. The prefix ‘amidino’ is no longer recommended. In the acyl group, the –NH₂ group is denoted by the locant N and the =NH group by N′.

The prefix ‘amidino’ is no longer acceptable in IUPAC nomenclature; ‘carbamimidoyl’ is now recommended for preferred IUPAC names.

Examples:

4-carbamimidoylbenzoic acid (PIN)
4-[amino(imino)methyl]benzoic acid
(not 4-amidinobenzoic acid)

4-(N′-ethyl-N,N-dimethylcarbamimidoyl)benzoic acid (PIN)
4-[(dimethylamino)(ethylimino)methyl]benzoic acid
[not 4-(N′-ethyl-N,N-dimethylamidino)benzoic acid]

Example:

methyl 4-(dimethylamino)-4-(ethylimino)butanoate (PIN)
(not methyl 3-[C-(dimethylamino)-N-ethylcarbonimidoyl]propanoate)
(not methyl 3-(N²-ethyl-N¹,N¹-dimethylamidino)propionate)

Example:

4-methanimidamidobenzoic acid (PIN)
4-[(iminomethyl)amino]benzoic acid
4-(formimidoylamino)benzoic acid

Example:

3-(S-aminosulfinimidoyl)propanoic acid (PIN)

(1) substitutively, by using a prefix formed by changing the final letter ‘e’ in the complete name of the amide to ‘o’, thus changing the suffixes ‘imidamide’ and ‘carboximidamide’ into ‘imidamido’ and ‘carboximidamido’, respectively, or ‘sulfonimidamide’ to ‘sulfonimidamido’, etc.

(2) substitutively, by using ‘acylamino’ prefixes formed by substituting the name of the acyl group to the substituent ‘amino’

Examples:

4-ethanimidamidobenzoic acid (PIN)
4-(acetimidoylamino)benzoic acid
4-acetimidamidobenzoic acid

2-(ethanesulfonodiimidamido)benzoic acid (PIN)
2-(ethanesulfonodiimidoylamino)benzoic acid

P-66.4.1.4.1 N-Substituted amidines are named by prefixing the name of the appropriate substituent to the name of the unsubstituted imidamides, with N and N′ as locants when there is only one imidamide suffix; the locant N refers to the amino group and N′ refers to the imino group. The locants N and N′ with superscripted numbers for example, N¹ or N′², are used when there are two or more imidamide suffixes. Because of tautomerism, the locants N, N′, etc. are used when only one substituent is present on each imidamide group.

The locants N and N′ are used for the NH2 and NH group of amidines, respectively, rather than the locants N1 and N2 which were used in the 1979 recommendations (ref. 1).

Examples:

N′-methyl-N,N-diphenylbenzenecarboximidamide (PIN)
(not N′-methyl-N,N-diphenylbenzenecarboxamidine)

N′-ethyl-N-methylbenzenecarboximidamide (PIN)
(not N′-ethyl-N-methylbenzenecarboxamidine)

N-phenylbenzenecarboximidamide (PIN)
(not N-phenylbenzenecarboxamidine;
not benzimidanilide)

N¹,N¹,N′³-triethyl-N′¹,N³,N³-trimethylnaphthalene-1,3-dicarboximidamide (PIN)

When geminal carboxamidine groups are present, the locants N, N′, N′′, N′′′ are used. Lowest locants are assigned to the most substituted group; when there is a choice, lowest locants are assigned to the first cited N-substituent. For polyamidines with at least one pair of geminal amidine groups, superscripted numerical locants indicating the position of the amidine group on a chain or cycle are used. This system of N-locants in association with superscript numerical locants is also recommended for naming disubstituted amines (see P-62.2.4.1) and disubstituted amides (see P-66.1.1.3.1.2).

Examples:

N′′′¹-ethyl-N¹,N¹-dimethylcyclohexane-1,1-dicarboximidamide (PIN)

N′′¹-ethyl-N¹,N¹,N³,N³-tetramethylcyclohexane-1,1,3-tricarboximidamide (PIN)

The compound H₂N-C(=NH)-S-S-C(=NH)-NH₂ and its derivatives have been named previously on the basis of the parent structure ‘formamidine disulfide’. They are now named on the basis of the parent compound ‘dicarbonic acid’ or as a dithioperoxyanhydride which is the preferred IUPAC name.

Example:

N-ethylcarbamimidic N-methylcarbamimidic dithioperoxyanhydride (PIN)
[not N¹-ethyl-N²-methyldisulfanedicarboximidamide (numbering shown);
not N-ethyl-N′′-methyl(dithioperoxy)dicarbonimidic diamide;
not N¹-ethyl-N³-methyl-α,α′-dithiobisformamidine (see C-951.5 in ref. 1)]

Note: The anhydride is the higher class in seniority (see P-41).

Diamidides are analogues of acyclic carboxylic anhydrides in which the =O atoms have been replaced by =NR groups and the anhydride oxygen atom by –NR– giving the general formula R-C(=NR′)-N(R′′)-C(=NR′′′)-R′′′ ′. Preferred IUPAC names are formed systematically as N-imidoylimidamides.

Example:

N-ethanimidoylethanimidamide (PIN)
N-acetimidoylacetimidamide
N-(1-iminoethyl)ethanimidamide

P-66.4.2.1 Amidrazone suffixes

Compounds having the general structure R-C(NH₂)=N-NH₂ or the tautomeric structure R-C(=NH)-NH-NH₂ have the class name ‘amidrazones’ and are named substitutively using the suffixes ‘hydrazonamide’ or ‘carbohydrazonamide’, and ‘imidohydrazide’ or ‘carboximidohydrazide’, respectively. N-Substitution, when the position of the double bond is known, is designated with the following locants:

for carbohydrazonamides
for carboximidohydrazides

When the position of the double bond is unknown, the senior characteristic group, carbohydrazonamide, is chosen to denote the tautomeric structure, with appropriate locants N and N′ to denote substitution. When the position of the substituted suffixes must be indicated in a name, locants designating the positions of the suffixes are superscripted to the appropriate N locants.

Retained names of amidrazones are formed by replacing the ‘amide’ ending in names of amides by ‘ohydrazonamide’ and are only used in general nomenclature. Preferred IUPAC names of amidrazones are formed systematically. Otherwise, the nomenclatural properties of amides are transferred to amidrazones; thus, preferred names of amidrazones correspond to preferred names of amides; and amides that are not substitutable generate nonsubstitutable amidrazones.

Examples:

ethanehydrazonamide (PIN)

benzenecarbohydrazonamide (PIN)

methanimidohydrazide (PIN)

cyclohexanecarboximidohydrazide (PIN)

N,N-dimethyl-N′-(propan-2-ylidene)methanehydrazonamide (PIN)
N,N-dimethyl-N′-isopropylideneformohydrazonamide
(not N,N-dimethylformamide isopropylidenehydrazone)

N′′-ethyl-N-methyl-N′-phenylbenzenecarboximidohydrazide (PIN)
N′′-ethyl-N-methyl-N′-phenylbenzimidohydrazide
(not N¹-methyl-N²-phenylbenzohydrazide ethylimide)

ethanediimidohydrazide (PIN)

ethanedihydrazonamide (PIN)

2-hydrazinyl-2-iminoethanehydrazonamide (PIN)

4-(2-nitrosohydrazine-1-carboximidoyl)tetraaz-3-ene-1-carboximidamide (PIN)
[an imidamide (an amidine) is senior to an imidohydrazide (an amidrazone)]

N³,N³-diethyl-N¹,N¹-dimethylnaphthalene-1,3-dicarbohydrazonamide (PIN)

N′¹,N′¹-diethyl-N′′′ ′¹,N′′′ ′¹-dimethylcyclohexane-1,1-dicarboximidohydrazide (PIN)
Note: For locants N, N′, etc. in association with numerical locants, see P-16.9, P-62.2.4.1.2 and P-66.4.1.4.2)

Example:

The general methodology discussed in P-65.2 is applied to generate the names for amidrazones derived from carbonic, di-, and polycarbonic acids.

Examples:

hydrazinecarboximidohydrazide (PIN)
carbonimidic dihydrazide

carbonohydrazonic diamide (PIN)

dicarbonimidic dihydrazide (PIN; see P-65.2.3.1)
(not 1,3-diimidodicarbonic dihydrazide)

dicarbonohydrazonic diamide (PIN; see P-65.2.3.1)
(not 1,3-dihydrazonodicarbonic diamide)

[(hydrazinecarboximidoyl)oxy]methanehydrazonamide (PIN)
[(carbamohydrazonoyl)oxy]methanimidohydrazide
[not [(hydrazinecarboximidoyl)oxy]formohydrazonamide]

P-66.4.2.3.1 Prefixes for the group –C(=NH)-NHNH₂ are ‘hydrazinecarboximidoyl’ (preferred prefix) derived from hydrazinecarboximidic acid, and ‘carbonohydrazidimidoyl’, derived from carbonohydrazidimidic acid. When this group is located at the end of a carbon chain, the prefixes ‘imino’ and ‘hydrazinyl’ are used in preferred IUPAC names in order to avoid fragmenting the parent chain.

Examples:

3-hydrazinyl-3-iminopropanoic acid (PIN)
(hydrazinecarboximidoyl)acetic acid
carbonohydrazidimidoylacetic acid
(C-hydrazinylcarbonimidoyl)acetic acid

3-(hydrazinecarboximidoyl)benzoic acid (PIN)
3-carbonohydrazidimidoylbenzoic acid
3-[hydrazinyl(imino)methyl]benzoic acid
3-(C-hydrazinylcarbonimidoyl)benzoic acid

Examples:

3-amino-3-hydrazinylidenepropanoic acid (PIN)
carbamohydrazonoylacetic acid

3-carbamohydrazonoylbenzoic acid (PIN)
3-[amino(hydrazinylidene)methyl]benzoic acid

Examples:

4-[(hydrazinylmethylidene)amino]benzoic acid (PIN)

H₂N-N=CH-NH-CH₂-CH₂-CN
N-(2-cyanoethyl)methanehydrazonamide (PIN)
(not 3-[(methanehydrazonoyl)amino]propanenitrile;
nor 3-[(hydrazinylidenemethyl)amino]propanenitrile)

Example:

3-[2-(aminomethylidene)hydrazin-1-yl]propanoic acid (PIN)

(1) substitutively, by using a prefix formed by changing the final letter ‘e’ in the complete name of the amide to ‘o’;

(2) substitutively, by using ‘acylamino’ prefixes formed by substituting the name of the acyl group to the substituent ‘amino’

Example:

(1) by expressing the corresponding hydrazide as a prefix by replacing the final letter ‘e’ in the name of the hydrazide by the letter ‘o’:

(2) as an acylhydrazinyl prefix; the hydrazinyl group is numbered by using the numerical locants 1 and 2.

Examples:

P-66.4.3.1 Hydrazidine suffixes

Compounds with the general structure R-C(=N-NH₂)-NH-NH₂ have the class name ‘hydrazidines’ and are named substitutively by using the suffixes ‘hydrazonohydrazide’ and ‘carbohydrazonohydrazide’ as prescribed for hydrazides. The former method of naming hydrazidines as hydrazones of the corresponding hydrazides (see C-954.2 in ref. 1) is no longer recommended.

Hydrazidines are named systematically in these recommendations rather than as hydrazones of the corresponding hydrazides as in the 1979 recommendations.

Locants are assigned to nitrogen atoms as follows:

Names of hydrazidines formally derived from carboxylic acids having retained names, formed by replacing the ‘ohydrazide’ ending in names of hydrazides by ‘hydrazonohydrazide’, may be used in general nomenclature. Preferred IUPAC names are formed systematically. Otherwise, the nomenclatural properties of hydrazides are transferred to hydrazidines; thus, preferred names of hydrazidines correspond to preferred names of hydrazides, and hydrazides that are not substitutable generate nonsubstitutable hydrazidines.

Examples:

methanehydrazonohydrazide (PIN)

butanehydrazonohydrazide (PIN)

ethanedihydrazonohydrazide (PIN)

N′,N′′-dimethylthiophene-2-carbohydrazonohydrazide (PIN)

N′,N′′-dibenzylidene-1,3-thiazole-4-carbohydrazonohydrazide (PIN)

N′², N′², N⁶,1-tetramethylnaphthalene-2,6-dicarbohydrazonohydrazide (PIN)

N′¹,N′¹-diethyl-N′′′ ′¹,N′′′ ′¹-dimethylcyclohexane-1,1-dicarbohydrazonohydrazide (PIN)

N′¹, N′¹-diethyl-N′′′ ′¹,N′′′ ′¹,N ³-trimethylcyclohexane-1,1,3-tricarbohydrazonohydrazide (PIN)
(for locants N, N′, etc. in association with numerical locants,
see P-16.9, P-62.2.4.1.2, P-66.3.1.2, P-66.3.3, P-66.4.1.1, P-66.4.1.4, and P-66.4.2.1)

Example:

benzenesulfinohydrazonohydrazide (PIN)

Examples:

hydrazinecarbohydrazonohydrazide (PIN)
carbonohydrazonic dihydrazide (P-65.2.1.3)

dicarbonohydrazonic dihydrazide (PIN, P-65.2.1.3)
(not dihydrazonodicarbonic dihydrazide)

P-66.4.3.4.1 In the presence of a senior characteristic group, the prefixes for the group –C(=N-NH₂)-NH-NH₂ are ‘hydrazinecarbohydrazonoyl’ (preferred prefix) or ‘C-hydrazinylcarbonohydrazonoyl’. When this group is located at the end of a carbon chain, the prefixes ‘hydrazinyl’ and ‘hydrazinylidene’ are preferred in order to avoid fragmenting the chain.

Examples:

3-hydrazinyl-3-hydrazinylidenepropanoic acid (PIN)
(hydrazinecarbohydrazonoyl)acetic acid
(C-hydrazinylcarbonohydrazonoyl)acetic acid

3-(hydrazinecarbohydrazonoyl)benzoic acid (PIN)
3-(C-hydrazinylcarbonohydrazonoyl)benzoic acid
3-[hydrazinyl(hydrazinylidene)methyl]benzoic acid

4-[C-(carbamimidoyloxy)methanimidohydrazido]benzoic acid (PIN)
4-{2-[C-(carbamimidoyloxy)methanimidoyl]hydrazin-1-yl}benzoic acid

Example:

[(hydrazinylmethylidene)hydrazinyl]acetic acid (PIN)

Amide oximes are formally oximes of carboxamides, i.e., compounds having the general structure R-C(=N-OH)-NH₂ and derivatives formed by substitution. Preferred IUPAC names are N′-hydroxy or N′-(alkyloxy) derivatives of carboximidamides (amidines). Suffixes such as ‘amide oxime’ or ‘carboxamide oxime’ are no longer recommended.

Examples:

N′-hydroxy-N-methylethanimidamide (PIN)
N′-hydroxy-N-methylacetimidamide
(not N-methylacetamide oxime)

N′-ethoxy-1H-imidazole-2-carboximidamide (PIN)
(not imidazole-2-carboxamide O-ethyloxime)

P-66.5.0 Introduction
P-66.5.1 Nomenclature for generating preferred names for nitriles
P-66.5.2 Substituted nitriles
P-66.5.3 Nitriles/cyanides corresponding to carbonic and di- and polycarbonic acids
P-66.5.4 Nitrile oxides and chalcogen analogues

Compounds with the general structure R-C≡N are called ‘nitriles’ or ‘cyanides’. Nitriles and cyanides are derived from hydrocyanic acid, H-C≡N. When the point of attachment of the –C≡N group to ‘R’ is a carbon atom or a heteroatom, these compounds form the class of nitriles and are named substitutively as nitriles. They may also be named as cyanides according to the principles of functional class nomenclature. In substitutive nomenclature formonitrile is the preferred IUPAC name. So, when substituted the compound is a preferred IUPAC name.

These two types of nomenclature are fully discussed in this Section.

P-66.5.1 Nomenclature for generating preferred names of nitriles

Compounds of the general structure R-C≡N have the class names ‘nitriles’ and are named in three ways:

(1) substitutively, using the suffixes ‘nitrile’ for –(C)N and ‘carbonitrile for –CN;

(2) by changing the ‘ic acid’ or ‘oic acid’ endings in retained names of carboxylic acids into ‘onitrile’; the nomenclatural properties of acids are transferred to nitriles; thus, preferred names of nitriles correspond to preferred names of carboxylic acids (see P-65.1.1.1) and carboxylic acids that are not substitutable generate nonsubstitutable nitriles (see P-65.1.1.2)

(3) by functional class nomenclature, using the class name ‘cyanide’

P-66.5.1.1.1 Acyclic mono- and dinitriles are named in the following two ways:

(1) substitutively by using the suffix ‘nitrile’; and

(2) by functional class nomenclature using the class name ‘cyanide’.

Examples:

hexanenitrile (PIN)
pentyl cyanide

pentanedinitrile (PIN)
propane-1,3-diyl dicyanide

Example:

butane-1,1,1-tricarbonitrile (PIN)

Examples:

Examples:

5-cyanofuran-2-carboxylic acid (PIN)
5-cyano-2-furoic acid

3-cyanopropanoic acid (PIN)

4-(cyanomethyl)heptanedinitrile (PIN)

P-66.5.1.2.1 The following names are preferred IUPAC names, with unlimited substitution, except for formonitrile whose substitution rules are the same as formic acid (see P-65.1.8) and, obviously, for oxalonitrile for which no substitution is possible.

Examples:

phthalonitrile
benzene-1,2-dicarbonitrile (PIN)

terephthalonitrile
benzene-1,4-dicarbonitrile (PIN)

Examples:

Examples:

L-xylononitrile (see P-102.5.6.6.2.1)

H₂N-CH₂-CN
aminoacetonitrile (see P-103.2.8)
glycinonitrile

Functional class nomenclature is used, when needed, to name compounds in accordance with the seniority of classes and to name compounds that cannot be named substitutively, for example, cyanides corresponding to sulfonic acid, sulfinic acids and their selenium and tellurium analogues, carbonic acid, cyanic acid, and inorganic acids.

P-66.5.1.3.1 Nitriles with an α-oxo group.

Compounds of the type R-CO-CN can be named as acyl cyanides in a way similar to acid halides. Since acyl cyanides are senior to nitriles, in the seniority of classes, functional class nomenclature must be used to express correctly the seniority order.

Examples:

Examples:

Substituents on the parent hydrides are denoted as prefixes. Nitriles, in the seniority order of classes, are senior to ketones, pseudoketones, heterones, hydroxy compounds, amines, and imines; these classes must be cited as prefixes in the presence of a nitrile group. Seniority for numbering of polyfunctional nitriles follows that described for acids, for which see P-65.1.2.3 and P-65.1.2.4.

Examples:

5-oxohexanenitrile (PIN)

4-hydroxybutanenitrile (PIN)
(not 4-hydroxybutyronitrile;
no substitution for this retained name, see P-65.1.1.2)

3-amino-1H-pyrazole-4-carbonitrile (PIN)

(3-bromophenyl)acetonitrile (PIN)

3,5-bis(2-aminoethyl)benzonitrile (PIN)

NC-CH₂-CH₂-NH-CH₂-CH₂-CN
3,3′-azanediyldipropanenitrile (PIN)
(not 3,3′-azanediyldipropionitrile;
no substitution on propionitrile, see P-65.1.1.2)

2-chloro-6-nitrobenzonitrile (PIN)

2-methoxybenzonitrile (PIN)

3-chloropropanoyl cyanide (PIN)
4-chloro-2-oxobutanenitrile
(not 3-chloropropionyl cyanide)

P-66.5.3.1 Nitriles corresponding to carbonic acid and di- and polycarbonic acids are named by functional class nomenclature.

Examples:

P-66.5.4.1 Compounds with the general structure R-C≡NO have the generic name ‘nitrile oxides’. As they may be considered as zwitterions, they are classed with zwitterions in the order of compound classes. They are named by three methods:

(1) by the term ‘oxide’, ‘sulfide’, ‘selenide’, or ‘telluride’ added to the name of the nitrile (see P-74.2.2.2.1.2).

(2) by applying the λ-convention and oxo substitution to the nitrogen atom (see P-14.1);

(3) as zwitterions (see P-74.2.2.2.1.2).

Examples:

Examples:

4-(methoxycarbonyl)benzonitrile oxide (PIN)
(not methyl 4-[(oxo-λ⁵-azanylidyne)methyl]benzoate)
(no longer methyl 4-isofulminatobenzoate)

sodium 4-[(oxo-λ⁵-azanylidyne)methyl]benzoate (PIN)
(no longer sodium 4-isofulminatobenzoate)

P-66.6.0 Introduction
P-66.6.1 Systematic names of aldehydes
P-66.6.2 Aldehydes from di- and polycarbonic acids
P-66.6.3 Chalcogen analogues of aldehydes
P-66.6.4 Polyfunctional aldehydes
P-66.6.5 Acetals and ketals, hemiacetals and hemiketals, and their chalcogen analogues

The class name ‘aldehyde’ traditionally refers to compounds containing the –CH=O group attached to a carbon atom. However, nomenclature for aldehydes has been extended to describe a –CHO group attached to a heteroatom.

P-66.6.1 Systematic names of aldehydes

Aldehydes are systematically named in three ways:

(1) substitutively, using the suffixes ‘al’ for –(C)HO and ‘carbaldehyde’ for –CHO;

(2) by changing the ‘ic acid’ or ‘oic acid’ endings of retained names of carboxylic acids into ‘aldehyde’; the nomenclatural properties of acids are transferred to aldehydes; thus, preferred names of aldehydes correspond to preferred names of acids, and carboxylic acids that are not substitutable generate nonsubstitutable aldehydes;

(3) by using the prefixes ‘oxo’, denoting =O, or ‘formyl-’, denoting the substituent group –CHO.

P-66.6.1.1.1 Mono- and dialdehydes derived from alkanes are named substitutively using the suffix ‘al’ added to the name of the parent hydride with elision of the final letter ‘e’ of the parent hydride before ‘a’.

Examples:

Example:

butane-1,2,4-tricarbaldehyde (PIN)

Examples:

cyclohexanecarbaldehyde (PIN)

pyridine-2,6-dicarbaldehyde (PIN)

H₂P-CHO
phosphanecarbaldehyde (PIN)

H₂NNH-CHO
hydrazinecarbaldehyde
formohydrazide (PIN;
hydrazide is senior to an aldehyde)

1,4,4-trimethyltetraaz-2-ene-1-carbaldehyde (PIN)

Names of aldehydes derived from retained names are formed by changing the ‘ic acid’ or ‘oic acid’ ending of the retained names of carboxylic acids to ‘aldehyde’. Substitution of aldehydes parallels that of corresponding carboxylic acids (see P-65.1.1.2).

P-66.6.1.2.1 The following names are preferred IUPAC names, with substitution allowed for acetaldehyde and benzaldehyde. Substitution rules for formaldehyde are the same as for formic acid (see P-65.1.8).

Examples:

phthalaldehyde
benzene-1,2-dicarbaldehyde (PIN)

terephthalaldehyde
benzene-1,4-dicarbaldehyde (PIN)

Examples:

Examples:

4-oxobutanoic acid (PIN)
3-formylpropanoic acid

4-formylcyclohexane-1-carboxylic acid (PIN)

2-(7-oxoheptyl)cyclopentane-1-carbaldehyde (PIN)
7-(2-formylcyclopentyl)heptanal
(ring preferred to chain: see P-44.1.2.2)

Aldehydes from di- and polycarbonic acids are named on the basis of the higher compound class. Multiplicative names based on formaldehyde can be used (see P-15.3.2.1).

Examples:

Chalcogen analogues of aldehydes are named by using the suffixes and prefixes in Table 6.4. In the seniority order of classes, aldehydes are senior to ketones, hydroxy compounds, amines, and imines. Names of chalcogen analogues corresponding to aldehydes with retained names are all systematically formed.

ethanethial (PIN)
thioacetaldehyde

C₆H₅-CHS
benzenecarbothialdehyde (PIN)
thiobenzaldehyde

hexaneselenal (PIN)

pentanedithial (PIN)

4-(methanethioyl)benzoic acid (PIN)
4-(thioformyl)benzoic acid

4-(methaneselenoyl)cyclohexane-1-carboxylic acid (PIN)
4-(selenoformyl)cyclohexane-1-carboxylic acid

4-sulfanylidenecyclohexane-1-carboselenaldehyde (PIN)
4-thioxocyclohexane-1-carboselenaldehyde

In the presence of an aldehyde group, ketones, pseudoketones, heterones, hydroxy compounds, amines, and imines are expressed by prefixes. Seniority for numbering polyfunctional aldehydes follows that described for acids, for which see P-65.1.2.3 and P-65.1.2.4.

Examples:

3-oxobutanal (PIN)
(not 3-oxobutyraldehyde)

2-methylidenehexanal (PIN)
[not 2-butylprop-2-enal,
the longest chain is the principal chain (see P-44.3)]

2-hydroxybenzaldehyde (PIN)
(not salicylaldehyde)

5-(hydroxymethyl)furan-2-carbaldehyde (PIN)
5-(hydroxymethyl)-2-furaldehyde
[not 5-(hydroxymethyl)furfural]

phenoxyacetaldehyde (PIN)

3-fluoro-2-methylbenzaldehyde (PIN)

P-66.6.5.1 Acetals and ketals
P-66.6.5.2 Hemiacetals and hemiketals
P-66.6.5.3 Chalcogen analogues of acetals and ketals

P-66.6.5.1.1 Compounds with the general structure RR′C(O-R′′)(O-R′′′), where only R and R′ may be, but need not be, hydrogen, have the class name ‘acetal’. ‘Ketals’ constitute a subclass of acetals wherein neither R nor R′ may be hydrogen. Acetals (ketals) are named in two ways:

(1) substitutively as ‘alkoxy’, alkyloxy, ‘aryloxy’, etc. derivatives of an appropriate parent hydride or functional parent compound;

(2) by functional class nomenclature by citing the name of the aldehyde or ketone, the names of the O-substituents, in alphanumerical order if required, and finally the class terms ‘acetal’ or ‘ketal’.

Examples:

(1) 1,1-diethoxypropane (PIN)
(2) propanal diethyl acetal

(1) 1-ethoxy-1-methoxycyclohexane (PIN)
(2) cyclohexanone ethyl methyl ketal

(1) 1,1-diethoxy-4,4-dimethoxycyclohexane (PIN)
(2) cyclohexane-1,4-dione 1,1-diethyl 4,4-dimethyl diketal

(1) 1-ethoxy-1,4,4-trimethoxycyclohexane (PIN)
(2) cyclohexane-1,4-dione 1-ethyl 1,4,4-trimethyl diketal

Cyclic acetals as the principal function are named as heterocyclic compounds and these names are preferred IUPAC names; cyclic ketals are spiro compounds that are named in accordance with the rules described in Section P-24 giving preferred IUPAC names.

Functional class nomenclature using the name of the appropriate divalent substituent groups may be used in general nomenclature.

Examples:

2-ethyl-1,3-dioxolane (PIN)
propanal ethylene acetal

1,4-dioxaspiro[4.5]decane (PIN)
cyclohexanone ethylene ketal

[2-(1,3-dioxolan-2-yl)ethyl]tri(methyl)silane (PIN)
3-(trimethylsilyl)propanal ethylene ketal

Compounds with the general structure RR′C(OH)(O-R′′) have the class name ‘hemiacetals’. They are named substitutively as ‘alkoxy’, ‘alkyloxy’, ‘aryloxy’, etc. derivatives of an appropriate hydroxy parent compound, such as an alcohol; these names are the preferred IUPAC names. Other names are formed by functional class nomenclature using the class name ‘hemiacetal’; similarly derivatives of ketones are denoted by the class name ‘hemiketal’.

Examples:

1-ethoxybutan-1-ol (PIN)
butanal ethyl hemiacetal

1-methoxycyclohexan-1-ol (PIN)
cyclohexanone methyl hemiketal

Sulfur analogues of acetals and ketals with the general structures RR′C(S-R′′)(S-R′′′), or RR′C(S-R′′)(O-R′′′), have the class names ‘dithioacetals’ or ‘monothioacetals’, respectively. They are named substitutively as ‘alkylsulfanyl’, ‘arylsulfanyl’, ‘alkoxy’, or ‘aryloxy’ derivatives, as appropriate, of a parent hydride; these names are preferred IUPAC names. Other names can be generated by functional class nomenclature, using class names such as ‘monothioacetal’ and ‘dithioketal’. Capital italic letter locants are used to provide structural specificity. Selenium, tellurium, and mixed chalcogen analogues are treated in the same way as their sulfur analogues.

Examples:

1,1-bis(methylsulfanyl)pentane (PIN)
pentanal dimethyl dithioacetal

1-(ethylsulfanyl)-1-methoxypropane (PIN)
propanal S-ethyl O-methyl monothioacetal

1-ethoxy-1-(ethylsulfanyl)cyclopentane (PIN)
cyclopentanone diethyl monothioketal

2-methyl-1,3-oxathiolane (PIN)
acetaldehyde ethylene monothioacetal

1-(ethylselanyl)-1-(methylsulfanyl)cyclohexane (PIN)
cyclohexanone Se-ethyl S-methyl selenothioketal

1-oxa-4-selenaspiro[4.4]nonane (PIN)
cyclopentanone ethylene monoselenoketal

Sulfur analogues of hemiacetals and hemiketals with the general structures RR′C(SH)(S-R′′), RR′C(OH)(S-R′′) or RR′C(SH)(O-R′′), have the class names ‘dithiohemiacetals’ or ‘monothiohemiacetals’, respectively. They are named substitutively as ‘alkylsulfanyl’, ‘arylsulfanyl’, ‘alkoxy’, or ‘aryloxy’ derivatives, as appropriate, of a hydroxy parent compound; these are preferred IUPAC names. Other names can be generated by functional class nomenclature. Capital italic letter locants are used to provide structural specificity. Selenium, tellurium, and mixed analogues are treated in the same way as their sulfur analogues; generically, they are ‘monoselenohemiacetals’, ‘ditellurohemiacetals’, ‘selenothiohemiacetals’, etc.

Examples:

1-(ethylsulfanyl)propane-1-thiol (PIN)
propanal ethyl dithiohemiacetal

1-ethoxypropane-1-thiol (PIN)
propanal O-ethyl monothiohemiacetal

1-(ethylsulfanyl)cyclopentane-1-selenol (PIN)
cyclopentanone S-ethyl selenothiohemiketal

P-67.0 Introduction
P-67.1 Mononuclear noncarbon oxoacids
P-67.2 Di- and polynuclear noncarbon oxoacids
P-67.3 Substitutive names and functional class names of polyacids

Mono-, di-, and polynuclear noncarbon oxoacids and their chalcogen analogues having retained names are used as parent structures to generate names of carbon containing compounds. In these recommendations, the names for these compounds are preselected names (see P-12.2)

Names of chalcogen analogues of noncarbon oxoacids are formed by functional replacement nomenclature. This type of nomenclature is also used to create derived classes, for example, acid halides and pseudohalides, amides, hydrazides, and amidines. With regard to functional replacement, mono- di- and polynuclear noncarbon acids do not constitute a homogeneous group. Names of mononuclear oxoacids are modified by infixes, with the exception of silicic acid, nitrous acid, nitric acid and the halogen acids. Names of the di- and polynuclear noncarbon oxoacids are modified by prefixes. Functional class nomenclature is used to generate names for esters, organic anhydrides, carbon containing pseudohalides such as cyanides and isocyanates, and organic derivatives of amides, imides, and hydrazides.

Mononuclear noncarbon oxoacids are discussed first, then di- and polynuclear noncarbon oxoacids, such as diphosphoric acid, (HO)₂P(O)-O-P(O)(OH)₂, which are named as acids, not as anhydrides, and hypodiphosphoric acid, (HO)₂P(O)-P(O)(OH)₂.

Systematization has been achieved, taking into consideration the nomenclature of inorganic compounds (ref. 12), that has restricted the use of retained names and of prefixes such as ‘hypo’, ‘ortho’, ‘iso’ added to the names of mononuclear oxoacids to generate retained names. However, the traditional nomenclature of organic compounds derived from mono-, di-, and polynuclear oxoacids has been maintained.

For carbonic, cyanic, di- and polynuclear carbonic acids, see P-65.2.

P-67.1 MONONUCLEAR NONCARBON OXOACIDS

Retained names for mononuclear noncarbon oxoacids have the following elements as central atoms: N, P, As, Sb, Si, B, S, Se, Te, F, Cl, Br, and I. They are used as parent structures and also for derivation of prefixes to be used in the presence of classes that have seniority for being named as parent compounds. These parent structures have retained names that are traditional names used as preselected names (see P-12.2). They may also have systematic additive or substitutive names, but these names are not recommended for generating preselected names (see IR-8, ref. 12)

Functional replacement nomenclature is discussed first; next the formation of esters and anhydrides using functional class nomenclature; and finally, substitutive nomenclature using prefixes is described. Application of the seniority order of oxoacids and their derivatives, described in Section P-42, is discussed. The Section ends with the nomenclature of aci-nitro compounds that are named as derivatives of azinic acid.

P-67.1.1 Names for mononuclear noncarbon oxoacids and their derivatives formed by substitution
P-67.1.2 Functional replacement nomenclature applied to noncarbon oxoacids
P-67.1.3 Salts, esters, and anhydrides of noncarbon oxoacids
P-67.1.4 Substituent prefix groups derived from mononuclear noncarbon oxoacids
P-67.1.5 Seniority order among noncarbon oxoacids and derivatives
P-67.1.6 aci-Nitro compounds

P-67.1.1.1 Names of mononuclear noncarbon oxoacids

Preselected names (see P-12.2) of the mononuclear noncarbon oxoacids used for deriving preferred IUPAC names for organic compounds and names for general organic nomenclature are noted in the following list, given in alphabetical order.

Acids with hydrogen atoms attached to the central atom may be substituted by organyl groups and preferred IUPAC names are formed in this manner.

Note: Another method has been suggested which would treat the acid as a suffix (like sulfonic acid) leading to names such as benzenephosphonic acid. This suggestion has been rejected because in cases where the acid has two substitutable hydrogen atoms, the use of additional letter locants would be required leading to unnecessarily more cumbersome names.

Examples:

Mononuclear noncarbon oxoacids are modified by either infixes or prefixes in functional replacement nomenclature.

P-67.1.2.1 Mononuclear acids modified by infixes
P-67.1.2.2 Mononuclear acids modified by prefixes
P-67.1.2.3 General methodology for functional replacement nomenclature using infixes
P-67.1.2.4 Mononuclear noncarbon oxoacids modified by functional replacement nomenclature
P-67.1.2.5 Acid halides and pseudohalides
P-67.1.2.6 Amides and hydrazides

P-67.1.2.2 Mononuclear noncarbon oxoacids modified by prefixes. The following acids are modified by prefixes; they are listed in the order Si, N, F, Cl, Br, I.

P-67.1.2.3 General methodology for functional replacement nomenclature using infixes

Functional replacement nomenclature (see P-15.5) using infixes generates functional class names for the following classes: acid halides and pseudo halides (azides, cyanides, isocyanides, and isocyanates), amides, hydrazides, and also imidic, hydrazonic and nitridic acids. Chalcogen analogues are also described by infixes.

Note: Preferred IUPAC names are retained names modified by functional nomenclature. The use of infixes is restricted to acids listed in P-67.1.2.1 and leads to preferred IUPAC names. Prefixes are used as recommended for acids listed in P-67.1.2.2, and in general nomenclature for all mononuclear acids. Substitutive names and names modified by prefixes are used only in special occasions (see P-67.1.4.1.1.6 and P-67.3.1).

Example:

P-67.1.2.3.2 Infixes denoting replacement of -OH group in decreasing order of seniority with all halides (class 1) and pseudohalides (class 2) having the same rank within the class.

P-67.1.2.3.4 Prefixes denoting replacement of -OH group in decreasing order of seniority with all halides (class 1) and pseudohalides (class 2) having the same rank within the class.

The appropriate prefix is indicated (in alphabetical order if there is more than one) before the name of the acid; no elision is recommended. Multiplying a prefix by multiplying prefixes ‘di’ or ‘tri’ does not change its place in the alphabetical order.

P-67.1.2.4 Mononuclear noncarbon oxoacids modified by functional replacement nomenclature

Preselected names described in P-67.1.2 are used for deriving preferred IUPAC names for organic compounds. As long as there is at least one –OH group left in an oxoacid having a retained name, the acid modified by functional replacement is classified as an acid and denoted by class name ‘acid’.

P-67.1.2.4.1 Functional replacement of the oxoacids specifically listed in P-67.1.2 is expressed by infixes or prefixes. Substitution of nonacidic hydrogen atoms is indicated by prefixes, with a letter locant B, N, P, As or Sb, as needed. Tautomers may be distinguished by prefixing italic elements symbols, such as S and O, to the term ‘acid’. Parentheses are needed to enclose infixes modified by a chalcogen prefix, for example, ‘thioperoxoic’. In addition to infixes and prefixes listed in P-67.1.2.3, the prefix ‘cyanato’ and the infix ‘cyanatido’, for –OCN, are used to modify acids as indicated in P-67.1.2.4.1.3.

P-67.1.2.4.1.1 Examples of mononuclear noncarbon oxoacids modified by infixes:

When attached to the central atom of a mononuclear noncarbon oxoacid, the group –OCN creates an anhydride linkage (see P-67.1.3.3). In order to respect the seniority order classes, this group is used, therefore, in functional replacement nomenclature to name acids; acids are senior to anhydrides. For the prefixes ‘cyanato’, ‘thiocyanato’, ‘selenocyanato’ and ‘tellurocyanato’, see P-65.2.2.

Examples:

The names phosphonous, phosphinous, phosphonic and phosphinic acid (and similarly for arsenic, antimony and nitrogen acids) can only be used when P, As or Sb is attached to atoms of hydrogen, carbon or another atom of a parent hydride such as N, As, Si. Thus, C₆H₅-P(O)Cl(OH) is phenylphosphonochloridic acid and not chloro(phenyl)phosphinic acid; (C₅H₁₀N)-P(O)Cl(OH) is (piperidin-1-yl)phosphonochloridic acid and not chloro(piperidin-1-yl)phosphinic acid; and ClP(O)(OH)₂ is phosphorochloridic acid and not chlorophosphonic acid.

P-67.1.2.5 Acid halides and pseudohalides

P-67.1.2.5.1 Except for the boron acids and silicic acid, preferred IUPAC names of acid halides and pseudohalides are formed by adding the class name(s) of a halide or pseudohalide to that of the acid. Exceptionally, in accordance with tradition and the recommended nomenclature of inorganic compounds (ref. 12), halides and pseudohalides with identical atoms or groups and derived from phosphoric acid, sulfuric acid, selenic acid and telluric acid are named by adding the class name(s) to the acyl group name ‘phosphoryl’, ‘sulfuryl’, ‘sulfamoyl’, ‘selenonyl’ and ‘telluronyl’, and not to the name of the acid itself. In accordance with the seniority order of halides and pseudohalides, names are formed on the basis of the senior class, as described in P-67.1.2.1.

Preferred IUPAC names of acid halides and pseudohalides derived from the boron acids and silicic acid are formed on the basis of the parent hydride names borane and silane, respectively.

Examples:

Examples:

C₆H₅-B(Cl)(Br)
bromo(chloro)(phenyl)borane (PIN)
phenylboronic bromide chloride
phenylboronobromidic chloride

CH₃-SiCl₃
trichloro(methyl)silane (PIN)

SiCl₄
tetrachlorosilane (preselected name)
silicon tetrachloride
(not silicic tetrachloride)

Amides and hydrazides are named by functional class nomenclature by replacing the term ‘acid’ in the name of the corresponding acid by ‘amide’ or ‘hydrazide’. Amides and hydrazides of nitric acid and nitrous acid are discussed in P-67.1.2.6.3. Preferred IUPAC names of amides and hydrazides of the boron acids and silicic acid are exceptions (see P-67.1.2.6.2) as are azorous acid, azinous acid and azonous acid which are names of polyazanes.

P-67.1.2.6.1 Preferred IUPAC names of amides and hydrazides are denoted by the class name ‘amide’ or ‘hydrazide’:

(a) when all –OH groups in the corresponding acid have been replaced by –NH₂ or –NH-NH₂ groups, and

(b) when the amide or hydrazide is the principal functional group in accordance with the following order of seniority:

Note: This order is not quite the same as that used by CAS (where amide follows the halogens and precedes the pseudohalogens) but it is consistent with the order of compound classes in P-41.

Substituents on the nitrogen atoms are denoted by italic letter locants such as, N (primed and double primed as required), in addition to the italic letter locants ‘P’, ‘As’, and ‘Sb’.

Locants to denote hydrazides are 1 and 2, primed and double primed as required.

Examples:

Examples:

Nitramines are amides of nitric acid (see ref. 23). The class is composed of ‘nitramide’ (a shortened form of nitric amide), NO₂-NH₂, and the names of its derivatives are formed by substitution. Nitrosamines are amides of nitrous acid, NO-NH₂ (see ref. 23); and the names of its derivatives are formed by substitution. Nitric acid and nitrous acid are preselected names, see P-12.

(I)

(II)

Preferred IUPAC names for amides and hydrazides of nitric and nitrous acids are now systematically based on nitric or nitrous amide and hydrazide, in accordance with the seniority order of classes rather than as nitro and nitroso amines; the latter names can be used in general nomenclature.

Examples:

The methodology discussed in this section is applicable to all mononuclear oxo acids whether or not they have retained names or names using infixes or prefixes.

P-67.1.3.1 Salts
P-67.1.3.2 Esters
P-67.1.3.3 Anhydrides

Neutral salts of mononuclear noncarbon oxoacids are named by citing the cation(s) followed by the name(s) of the anion(s) as a separate word. Names of anions are formed by changing the ‘ic acid’ ending to ‘ate’ and the ‘ous acid’ ending to ‘ite’. Different cations are cited in alphabetical order.

Examples:

Note: In the nomenclature of inorganic chemistry (IR-8.4, ref. 12), the term ‘hydrogen’ is written directly in front of the name of the anion, without a space, to indicate that it is part of the anion.

Example:

Esters of mononuclear noncarbon acids are named in the same way as esters of organic acids (see P-65.6.3.2). Alkyl groups, aryl groups, etc. are cited as separate words, in alphanumerical order when more than one, and followed by the name of the appropriate anion. Partial acid esters of polybasic acids are named by citing alkyl groups, aryl groups, etc. as separate words, in alphanumeric order if more than one, followed by the word ‘hydrogen’ (with the appropriate multiplying prefix, as necessary) also cited as a separate word, and the name of the appropriate anion. Salts of partial acid esters are named by citing the name of the cation before the name of the organic group; remaining acids groups are denoted by the word ‘hydrogen’ as described above. Structural specificity for esters of chalcogen analogues of mononuclear noncarbon oxoacids is provided by the appropriate italic element symbols O, S, Se, and Te, prefixed to the name of the group, as needed.

Examples:

Neutral anhydrides formed between acids named by suffixes and mononuclear noncarbon oxoacids described in P-67.1.1 are named in the same way as described for anhydrides derived from carboxylic and the sulfur acids named by suffixes (see P-65.7). The names of the acids are cited in alphabetical order followed by the class name ‘anhydride’ prefixed by a numerical term indicating the number of anhydride linkages (the numerical prefix mono is not used); such names lead to preferred IUPAC names. Names formed by acyl groups substituting the phosphorus, arsenic or antimony mononuclear oxoacid modified by the ending ‘ate’ can be used in general nomenclature. Halogen oxoacids form anhydrides with carboxylic and the sulfur acids expressed by suffixes.

Acidic anhydrides are named as described in P-67.3.1 using the senior acid as parent, or by using systematic substitutive nomenclature.

Examples:

P-67.1.4.1 Substituent groups derived from the mononuclear nitrogen, phosphorus, arsenic, and antimony acids
P-67.1.4.2 Substituent groups derived from boron acid and silicic acid
P-67-1.4.3 Substituent groups derived from nitric and nitrous acids
P-67.1.4.4 Substituent groups derived from chalcogen acids
P-67.1.4.5 Substituent groups derived from halogen acids

P-67.1.4.1.1 Preselected prefixes
P-67.1.4.1.2 Substituent groups for general nomenclature
P-67.1.4.1.3 Compound and complex substituent groups

Substituent prefix groups derived from mononuclear noncarbon oxoacids have retained names and systematic names corresponding to simple or compound acyl groups. The preselected prefixes are formed by applying the following seniority order, in the order given, until a decision is reached:

P-67.1.4.1.1.1 Retained names for substituent groups derived from mononuclear noncarbon oxoacids;

A few names denoting monovalent acidic groups are retained. These names are preselected names when unsubstituted or for chalcogen analogues when the position of chalcogen atoms introduced by functional replacement is not known or it is not necessary to specify their position(s): the chalcogen atoms are expressed by prefixes.

P-67.1.4.1.1.2 Fundamental acyl groups for substituents derived from mononuclear noncarbon oxoacids;

Acyl prefix groups are formed by removing all –OH groups from a mononuclear noncarbon oxoacid having the general structures E(=O)(OH)₃, R-E(=O)(OH)₂ or R,R′E(=O)OH, where R and R′ = H or an organyl group. Names of acyl groups derived from the names of acids, modified or not by functional replacement, by elimination of all hydroxy groups or their chalcogen analogues, are formed by changing the ‘ic acid’ ending in the name of the acid to ‘oyl’, with the exception of ‘nitroryl’ –N(O)<; ‘phosphoryl’, –P(O)<; ‘arsoryl’, –As(O)<; and ‘stiboryl’, –Sb(O)<. Prefixes formed in this manner are preselected prefixes. For example, the group ‘phosphoryl’ –P(O)<, is derived from phosphoric acid, P(O)(OH)₃ or phosphorothioic S-acid, P(O)(OH)₂(SH), or phosphorodithioic S,S-acid, P(O)(SH)₂(OH) or phosphorotrithioic S,S,S-acid, P(O)(SH)₃.

The prefix ‘nitroryl’ (not azoryl), for the acyl group –N(O)<, derived from the hypothetical nitroric acid, N(O)(OH)₃, has been recommended since 1993 (see R-3.3, ref. 2).

Examples:

P-67.1.4.1.1.3 Names of substituted fundamental acyl groups derived from mononuclear noncarbon oxoacids

Names of substituted fundamental acyl groups are formed directly from those of the acids generated by the method described in P-67.1.4.1.1.2. Preferred prefix names of acyl groups are those derived from the preferred IUPAC names of acids. The addition of hydrogen atoms to acyl groups by the method of concatenation, described in P-67.1.4.1.2, is not allowed.

Examples:

P-67.1.4.1.1.4 Names of acyl groups derived from mononuclear noncarbon oxoacids modified by functional replacement nomenclature

Preferred IUPAC prefixes are formed by the methodology indicated in P-65.2.1.5 for acyl groups derived from carbonic acids modified by the infixes and prefixes in functional replacement nomenclature. All infixes and prefixes listed in Table 1.6 and cited in P-65.1.2.3 are allowed. Applied to the B, N, P, As and Sb mononuclear noncarbon oxoacids, the method consists of first achieving functional replacement in acids, then removing all remaining –OH groups. Preselected names use infixes to denote functional replacement. Names using prefixes to effect functional replacement may be used in general nomenclature.

Examples:

P-67.1.4.1.1.5 Names for preferred or preselected prefixes of acyl groups substituted by hydroxy groups or their chalcogen and peroxy analogues.

Concatenation is the recommended method to reintroduce groups and their chalcogen analogues in substituent groups or groups that are not treated as infixes in functional replacement nomenclature, such as ‘–OR’, ‘–SR’, etc. It is important to respect the concatenation procedure that is an additive operation using acyl groups only. The following acyl groups are allowed: basic acyl groups described in P-67.1.4.1.1.2 above, substituted basic acyl groups described in P-67.1.4.1.1.3 above, and acyl groups modified by functional replacement described in P-67.1.4.1.1.4 above. Substitution of hydrogen atoms attached to the central atom (substitutable hydrogen) in the basic acyl groups described in P-67.1.4.1.1.2 above is not allowed to generate preferred IUPAC names.

This method is not recommended to generate any of the prefixes in P-67.1.4.1.1.1 above.

Examples:

Substitutive nomenclature based on parent hydrides BH₃, PH₃, AsH₃, SbH₃, PH₅, AsH₅, SbH₅ is used to generate names of substituent groups for which acyl group names cannot be generated by the methods in P-67.1.4.1.1.1 through P-67.1.4.1.1.5 and the corresponding As and Sb acids. It is also used to indicate a different type of free valencies, for example an ‘ylidene’ type instead of the ‘diyl’ observed in a substituent group derived from the acid in criteria (b) and (d).

Examples:

The prefix ‘hydro’ may be added by concatenation only for use in general nomenclature.

Examples:

If a B, N, P, As, or Sb containing group is attached by an oxygen or other chalcogen atom or a nitrogen atom to a compound that also contains another substituent having priority over the B, N, P, As, or Sb containing group for citation as principal group, then the B, N, P, As, or Sb containing group is named by a compound or complex prefix built from prefixes described above and arranged in the order in which the components occur in the compound.

Examples:

Substituent groups derived from boron and silicon mononuclear acids and their analogues are formed by substituting the parent hydride names ‘borane’ and ‘silane’. The name borono, for –B(OH)₂, is retained and is the preselected name.

The name boryl has been used for the substituent group H₂B–, now named boranyl as the preselected name, and consequently is not to be used for the prefix group derived from boric acid by removal of all three –OH groups.

Examples:

The acyl groups ‘nitro’ for –NO₂ and ‘nitroso’ for –NO when attached to the following elements C, P, As, Sb, Bi, Si, Ge, Sn, Pb, B, Al, Ga, In, and Tl were discussed in P-61.5. In this section, the rules for naming substituent groups related to esters, amides and hydrazides of nitric acid and nitrous acid are discussed.

P-67.1.4.3.1 Substituent groups derived from esters of nitric acid and nitrous acid

Nitrates and nitrites as esters of nitric acid and nitrous acid are discussed in P-67.1.3.2. Substituent groups derived from these compounds are named by concatenation by adding the acyl groups ‘nitro’ for –NO₂ and ‘nitroso’ for –NO to the prefix ‘oxy’ or by substituting these acyl groups into substituent groups such as ‘sulfanyl’ , ‘selanyl’, or ‘tellanyl’.

Examples:

The amide of nitric acid, O₂N-NH₂, is named ‘nitramide’ and the substituent group derived from this amide by the loss of one hydrogen atom is called ‘nitramido’ by applying the general rule for naming amides (see P-66.1.1.4.3); that is, changing the final letter ‘e’ of the amide name to ‘o’. Other derivatives and those derived from nitrous amide, ON–NH₂, are formed by substituting the acyl groups ‘nitro’ and ‘nitroso’ into the appropriate substituent groups ‘amino’, ‘imino’, and ‘azanetriyl’. It must be noted that the location of the groups –NO and –NO₂ to another nitrogen atom does not constitute lengthening of a chain.

Examples:

Substituent groups derived from nitric hydrazide, O₂N-NH-NH₂, and nitrous hydrazide, ON-NH-NH₂, are named by substituting the acyl groups ‘nitro’ or ‘nitroso’ into the appropriate substituent group ‘hydrazin-1-yl’, ‘hydrazin-1-ylidene’, etc.

Examples:

2-nitrohydrazin-1-yl (preselected prefix)

nitrosohydrazinylidene (preselected prefix)

1-nitrohydrazin-1-yl (preselected prefix)

P-67.1.4.4.1 Acyl groups

There are two methods to generate names of acyl groups derived from the chalcogen acids for use as substituent groups.

(1) The methodology described in P-65.3.2.3, i.e., infixes denoting functional replacement by -S-, -Se-, -Te-, =NH, and =NNH₂, and concatenation for other atoms or groups.

(2) The general method described in P-65.2.1.5 for deriving acyl groups from derivatives of carbonic acid, and applied in P-67.1.4.1.1.4 for acyl groups derived from phosphoric, phosphonic and phosphinic acids and their arsenic and antimony congeners is applied to sulfuric acid and its functional replacement analogues.

Examples:

P-67.1.4.4.2 If a sulfur-containing group is attached by oxygen (chalcogen) or nitrogen to a compound that contains also another substituent having priority over the sulfur- containing group for citation as principal group, then the sulfur-containing group is named by an appropriate prefix formed by concatenation or substitution (see P-35.4) as described in P-65.3.2.3 and P-67.1.4.4.1.

Examples:

3-(sulfooxy)propanoic acid (PIN)

3-[(methoxysulfinyl)oxy]propanoic acid (PIN)

3-[(chlorosulfonyl)oxy]propanoic acid (PIN)
3-(sulfurochloridoyloxy)propanoic acid

3-(sulfamoyloxy)propanoic acid (PIN)
3-(sulfuramidoyloxy)propanoic acid
[not 3-(sulfonamidoyloxy)propanoic acid;
the name sulfonamidic acid is not an approved name]

3-[(aminosulfinyl)oxy]propanoic acid (PIN)
[not 3-(sulfinamidoyloxy)propanoic acid;
the name sulfinamidic acid is not an approved name]

3-[(methoxysulfonyl)amino]propanoic acid (PIN)

Names of prefixes derived from halogen acids and their chalcogen analogues are used as compulsory prefixes in substitutive nomenclature. They are listed in Table 5.1 and discussed in P-61.3.2.3.

Examples:

Example:

P-67.1.5.1 When a characteristic group having priority to be cited as principal group is present (see seniority order of classes, P-41, and of acids, P-42), prefixes having retained names or names systematically formed (see P-67.1.4.1) are used to denote inorganic acids.

Examples:

4-(dihydroxyarsanyl)benzoic acid (PIN)
[–COOH is senior to –As(OH)₂]

(HO)₂P(O)-CH₂-COOH
phosphonoacetic acid (PIN)

[2-(methoxysulfonyl)phenyl]phosphonic acid (PIN)
(an acid is senior to an ester)

(4-arsonobutyl)phosphonic acid (PIN)
(a phosphorus acid is senior to an arsenic acid)

C₆H₅-SO₂-N=P(NH-C₆H₅)₃
N-(trianilino-λ⁵-phosphanylidene)benzenesulfonamide (PIN)
N-(trianilinophosphoranylidene)benzenesulfonamide
[not N,N′,N′′-triphenyl-N′′′-benzenesulfonylphosphorimidic triamide;
nor N′′′-benzenesulfonylphosphorimidic tris(phenylamide)]

Examples:

aci-Nitro compounds deserve a special mention. They are tautomers of nitro compounds having the general structure R=N(O)OH or R₂N(O)OH and are named as derivatives of azinic acid, H₂N(O)OH.

Example:

The name ‘hydroxy(oxo)-λ5-azanylidene’ is a change from the 1993 (ref. 2) recommended name ‘hydroxynitroryl’, that is not acceptable in the context of these recommendations where two free valencies must be expressed by the correct ‘ylidene’ or ‘diyl’ type.

Examples:

Like mononuclear acids, polynuclear acids have retained names that are used as preselected names. Substitutive or additive names are not recommended. Retained names are used as parents and are modifiable by functional replacement in the same manner that mononuclear acids are, except that only prefixes are used for the functional replacement operation.

Di- and polynuclear noncarbon oxoacids, whose central atoms are B, P, As, Sb, S, Se, are described here. They are divided into three types. Di- and trinuclear acids are exemplified for each central atom. In some cases higher polynuclear acids are known. Their names are formed by using the appropriate multiplying prefixes to indicate the number of central atoms. Di- and polynuclear noncarbon oxoacids are discussed in Sections P-67.2 and P-67.3.

Insofar as their structures are known and conform to those of the phosphorus acids, arsenic and antimony acids are named in the same way as those of phosphorus, with ‘ars’ and ‘stib’, respectively, in place of ‘phosph’. Similarly, tellurium acids are named in the same way as those of selenium, by changing ‘selen’ to ‘tellur’ in the names of acids.

P-67.2.1 Preselected names
P-67.2.2 Functional replacement derivatives of di- and polynuclear noncarbon oxoacids
P-67.2.3 Acid halides and pseudohalides of di- and polynuclear noncarbon oxoacids
P-67.2.4 Amides and hydrazides of di- and polynuclear noncarbon oxoacids
P-67.2.5 Esters and anhydrides of di- and polynuclear noncarbon oxoacids
P-67.2.6 Substituent groups derived from polyacids

The following traditional names are retained as preselected names (for consistency in the names of polynuclear oxoacids, the numerical infix ‘di’ has been uniformly used in naming dinuclear ‘hypo’ acids). Although the ‘meta’ acids are for general nomenclature only, they are preselected names if the structure is unknown.

For consistency in the names of polynuclear oxoacids, the numerical infix ‘di’ has been uniformly used in naming dinuclear ‘hypo’ acids, for example, hypodiphosphorous acid, rather than hypophosphorous acid.

P-67.2.2.1 General methodology
P-67.2.2.2 Replacement by –OO–, –S–, =S, –Se–, =Se, –Te–, =Te, –NH–, and =NH

Prefixes are used to indicate functional replacement of polynuclear noncarbon oxoacids, listed in P-67.1.2.3.3 and P-67.1.2.3.4. The prefixes are cited and numbered in alphabetical order in front of the retained name of the polyacid, with appropriate locants as required. Each acid is numbered from one end to the other, starting from and finishing at a central atom. Before applying the functional replacement operation, the principal function must be selected; it receives the lower locant. The order of functions to be considered is: acids (see P-67.2.2.2), acid halides and pseudohalides (see P-67.2.3), amides and hydrazides (see P-67.2.4).

P-67.2.2.2 Replacement by –OO–, –S–, =S, –Se–, =Se, –Te–, =Te, –NH–, and =NH

Functional replacement of oxygen atom(s) is denoted by prefixes, i.e., peroxy, for –OO–; thio, for –S– or =S; seleno, for –Se– or =Se; telluro, for –Te– or =Te; and imido, for –NH– or =NH. Superscripted italic letter locants N¹ N² are used to designate substitution on imido groups that are not linkages between atoms that receive numerical locants as part of the chain. For rules on primes, see P-16.9.

The use of superscripted ‘N’ locants is a change from previous recommendations serially letters for example, ‘N′’, ‘N′′’, etc. ; the priming serially follows the arabic numbers of the chain, the number of primes parallels the increasing value of the arabic numbers.

Superscripted italic letters are used to specifically locate the chalcogen atoms in acid groups, for example S³.

This is a change from previous recommendations where the specific location of a chalcogen atom in acid groups was described by an on line arabic number prefixed to the atomic symbol.

Examples:

1,3-dithiotriphosphoric S¹,S³-acid
(not 1,3-dithiotriphosphoric 1-S,3-S-acid)
(name derived from the preselected name triphosphoric acid)

1-thiodiphosphoric S¹-acid (name derived from the preselected name diphosphoric acid;
the ‘thio’ replacement determines locant ‘1’)

2-seleno-1,1,3-trithiodiarsonic S¹,S³-acid
(name derived from the preselected name diarsonic acid;
the ‘dithio’ replacement for one acid group determines the locant ‘1’)

1,3-dithiodiphosphonic O¹,S³-acid
(name derived from the preselected name diphosphonic acid;
the ‘OH’ group of the acid function is alphabetically preferred for lower locant to the ‘SH’ group)

1-imidohypodiarsonic acid
(name derived from the preselected name hypodiarsonic acid;
the ‘imido’ replacement prefix determines the locant ‘1’)

1,3-diimidodiphosphoric acid
(name derived from the preselected name diphosphoric acid)

1-thiodisulfuric S¹-acid
(name derived from preselected name disulfuric acid)

3-amido-1-selenodisulfuric Se¹-acid
(name derived from the preselected name disulfuric acid;
the acid determines the locant ‘1’)

2-thiodisulfuric acid (preselected name)
sulfanedisulfonic acid
trithionic acid (traditional name)

2-(dithioperoxy)disulfuric acid (preselected name)
disulfanedisulfonic acid
tetrathionic acid (traditional name)

2,4-diimidotrisulfuric acid
(name derived from the preselected name trisulfuric acid)

N¹-methyl-1-imido-2-thiodithionous S²-acid (PIN;
the ‘imido’ replacememt prefix determines the locant ‘1’
[not 1-(methylimido)-2-thiodithionous 2-S-acid]

N¹-methyl-1,2-diimidodithionous acid (PIN)

2-imido-1,1,3-trithiodisulfuric O³,S¹-acid
(name derived from the preselected name disulfuric acid)

1-imido-1,3-dithiodisulfuric O¹,S³-acid
(name derived from the preselected name disulfuric acid;
the ‘OH’ group of the acid function is alphabetically preferred for lower locant to the ‘SH’ group)

Acid halides and pseudohalides, in which all OH groups have been replaced by halides or pseudohalide atoms or groups, are named by functional class nomenclature by replacing the name ‘acid’ by the name of the appropriate halide or pseudohalide. For acid halides and acid pseudohalides the senority is halides (alphabetical) followed by the following seniority for the halogenides: N₃, CN, NC, NCO, NCS, NCSe, NCTe.

Examples:

2-imidodiphosphonic 1-bromide 3-chloride
(name derived from the preselected name diphosphonic acid;
the ‘Br’, bromide, is preferred to ‘Cl’, chloride (alphabetically) and determines the locant ‘1’)

2-thiodiphosphoric tetrachloride
(name derived from the preselected name diphosphoric acid)

diphosphoric tetraisocyanate (PIN)

cyanohypodiphosphorous triiodide (PIN)

3-amido-2-imidodiphosphonic chloride
(name derived from the preselected name diphosphonic acid,
the acid chloride is preferred to the amide group and determines the locant ‘1’)

Polynuclear noncarbon oxoacids in which all –OH groups have been replaced by –NH₂ or –NHNH₂ groups are named as amides or hydrazides, respectively, by functional class nomenclature. Amides are expressed by the class name ‘amide’, preceded by an appropriate multiplying prefix, ‘di’, ‘tri’, etc. Similarly, hydrazides are expressed by the class name ‘hydrazide’. Functional replacement is described by prefixes cited before the whole name and not in front of the class name. Italic letter locants N, N′, etc. and superscripted letter locants N¹, N′¹, etc. are used to designate substitution on nitrogen atoms that are not linkages between central atoms that receive numerical locants as part of the chain. When a choice is needed, amides are senior to hydrazides, and receive the lower locants.

Examples:

hypodiphosphoric tetraamide
(name derived from the preselected name hypodiphosphoric acid)

hypodiphosphonic diamide
(name derived from the preselected name hypodiphosphonic acid)

diphosphoric tetraamide
(name derived from the preselected name diphosphoric acid)

2,4-diimidotrisulfuric diamide
(name derived from the preselected name trisulfuric acid)

diphosphonic dihydrazide
(name derived from the preselected name diphosphonic acid)

2-thiodiphosphoric tetraamide
(name derived from the preselected name diphosphoric acid)

triphosphonic diamide
(name derived from the preselected name triphosphonic acid)

N¹-methyl-1,2,3-triimidodiphosphoric tetraamide (PIN)

2,4-diimidotriphosphoric pentaamide
(name derived from the preselected name triphosphoric acid)

2,4,6-triimidotetraphosphoric hexaamide
(name derived from the preselected name tetraphosphoric acid)

pentaimidotriphosphoric pentaamide
(name derived from the preselected name triphosphoric acid)

heptaimidotetraphosphoric hexaamide
(name derived from the preselected name tetraphosphoric acid)

H₂N-SO₂-O-SO₂-NH₂
disulfuric diamide
(name derived from the preselected name disulfuric acid)

H₂N-SeO₂-O-SeO₂-NH₂
diselenic diamide
(name derived from the preselected name diselenic acid)

3-hydrazidodiphosphonic 1-amide

1,3-dihydrazidodiphosphoric 1,3-diamide

P-67.2.5.1 Salts of di- and polybasic noncarbon oxoacids
P-67.2.5.2 Esters of polybasic noncarbon oxoacids
P-67.2.5.3 Anhydrides of polybasic noncarbon oxoacids

P-67.2.5.1.1 Neutral salts of di- and polynuclear noncarbon oxoacids are named by citing the cation(s) followed by the name of the anion(s) as (a) separate word(s). Names of anions are formed by changing the ‘ic acid’ ending to ‘ate’ and the ‘ous acid’ to ‘ite’. Different cations are cited in alphabetical order.

Examples:

disodium N-methyl-1,2-diimidodithionite (PIN)

4 Na⁺   (^–O)₂P(=O)-O-P(=O)(O^–)₂
tetrasodium diphosphate
(name derived from the preselected name diphosphoric acid)

Example:

Fully esterified polynuclear noncarbon oxoacids are named as neutral salts, except that names of allowed groups (alkyl groups, aryl groups, etc.), cited in alphanumerical order when more than one, replace the name of the cations. Partial (acid) esters of polybasic noncarbon oxoacids and their salts are named by the procedures for neutral esters and acid salts, except that the name ‘hydrogen’ denoting acid hydrogen atoms is indicated by the separate word ‘hydrogen’ (with the appropriate multiplying prefix denoting multiplicity) inserted between the name of the cation or of the organic group and the name of the anion.

Examples:

dimethyl thiohypodiphosphonite (PIN)

methyl hydrogen dithiohypodiphosphonite (PIN)

CH₃-O-SO₂-O-SO₂-S-CH₂-CH₃
S-ethyl O-methyl thiodisulfate (PIN)

(CH₃)₂CH-O-SO-O-SO-O-CH(CH₃)₂
1,3-bis[(propan-2-yl)oxy]-1λ⁴,3λ⁴-dithioxane-1,3-dione (PIN)
[not di(propan-2-yl) disulfite, see P-67.3.2]

CH₃-O-SO₂-S-SO₂-O-CH₃
O¹,O³-dimethyl thiodisulfate (PIN)

Neutral anhydrides formed between organic acids and polynuclear noncarbon oxoacids having preselected names are named by citing, in alphabetical order, the names of the acids followed by the name of the class ‘anhydride’; multiplying prefixes ‘di’, ‘tri’, etc. are used to indicate the multiplicity of the anhydride linkages.

Acidic anhydrides are named by using the senior acid as parent or by using systematic substitutive nomenclature as described in P-67.3.1.

Examples:

In the presence of a characteristic group having precedence for citation as principal group, polynuclear noncarbon oxoacids are cited as prefixes. The names of these prefixes are formed by:

(1) combinations of acyl groups;

(2) on the basis of the names of the group which includes the greatest number of P, As, Sb, S, Se, and Te central atoms.

(3) skeletal replacement nomenclature (see P-15.4 and P-51.4), when conditions for its use are satisfied.

Examples:

(2) 3-[(1,3,3-trihydroxy-1,3-dioxo-1λ⁵,3λ⁵-diphosphoxan-1-yl)oxy]propanoic acid (PIN)
(1) 3-{[hydroxy(phosphonooxy)phosphoryl]oxy}propanoic acid

(3) 3,5,7-trioxo-2,4,6,8-tetraoxa-3λ⁴,5λ⁴,7λ⁴-trithiadecan-10-oic acid (PIN)
(1) {[({[(methoxysulfinyl)oxy]sulfinyl}oxy)sulfinyl]oxy}acetic acid
(2) [(5-methoxy-1,3,5-trioxo-1λ⁴,3λ⁴,5λ⁴-trisulfoxan-1-yl)oxy]acetic acid

(3) 3,5-bis(sulfanylidene)-2,3λ⁴,4,5λ⁴,6-pentathianonan-9-oic acid (PIN)
(2) 3-[5-methyl-2,4-bis(sulfanylidene)-2λ⁴,4λ⁴-pentasulfanyl]propanoic acid
(1) 3-[({[(methylsulfanyl)sulfinothioyl]sulfanyl}sulfinothioyl)sulfanyl]propanoic acid

P-67.3.1 Names of polynuclear noncarbon oxoacids that cannot be formed on the basis of fundamental oxoacids are either named by using class names, such as anhydrides, or they are formed substitutively. Anhydride names are preferred to substitutive names.

Some names are also included in this Section because their structure does not correspond to the name implied by a diacid or a hypodiacid, for example the name ‘disulfurous acid’, exemplified below.

Names of derivatives of acids that cannot be formed directly by functional replacement are generated by substitution of acids with preferred names such as phosphonic acid and phosphinic acid; or they are class names such as ‘anhydride’. The parent is chosen in accordance with the seniority order of classes: acids, acid halides, azides, cyanides, isocyanides, isocyanates (and chalcogen analogues in the order O > S > Se > Te), amides, hydrazides, and the maximum number of groups representing the senior class (see P-67.1.2.3.2).

Examples:

{[amino(hydroxy)phosphanyl]oxy}phosphonamidic acid (preselected name)
(phosphonamidic acid is senior to phosphonamidous acid)
phosphoramidic phosphoramidous monoanhydride
(an acid is preferred to an anhydride in the seniority order of classes)

phosphorodiamidic phosphorodiamidous anhydride (preselected name)
[(diaminophosphanyl)oxy]phosphonic diamide
(an anhydride is senior to an amide)

(arsonosulfanyl)phosphonic acid (preselected name)
arsoric phosphoric thiomonoanhydride
(an acid is senior to an anhydride; the phosphorus acid is senior to the arsenic acid)

N-(hydroxyphosphonoyl)phosphoramidic acid (preselected name)
(only a substitutive name is possible in this case)

(HO)₂P-HP(O)-OH
(dihydroxyphosphanyl)phosphinic acid (preselected name)

(CH₃-O)₂P(O)-O-HP(O)-O-CH₃
methyl [(dimethoxyphosphoryl)oxy]phosphonate (PIN)
(phosphonic acid is senior to phosphoric acid; see P-42)
(formerly trimethyl isohypophosphate)

(CH₃)₂P-P(OH)-P(CH₃)₂
bis(dimethylphosphanyl)phosphinous acid (PIN)
(not 1,1,3,3-tetramethyltriphosphan-2-ol;
the acid is senior to the heterol)

1-hydroxy-1,1-diiodo-1λ⁴-disulfane-2-carbonitrile (PIN)
(formerly diiodo(thiocyanatido)orthosulfurous acid)
(not orthosulfurodiiodidothiocyanatidous acid)

methyl hydrogen {[ethoxy(hydroxy)boranyl]oxy}phosphonate (PIN)
(ethyl dihydrogen borate) (methyl dihydrogen phosphate) anhydride

CH₃-CO-O-P(O)(OH)₂
(acetyloxy)phosphonic acid (PIN)
acetic phosphoric monoanhydride
monoacetyl phosphate

HO-SeO₂-O-SO₂-OH
selenic sulfuric anhydride (preselected name)
(selenonooxy)hydroxy-λ⁶-sulfanedione

CH₃-CH₂-CO-O-B(OH)₂
(propanoyloxy)boronic acid (PIN)
boric propanoic monoanhydride

CH₃-CO-O-CO-O-CO-OH
{[(acetyloxy)carbonyl]oxy}formic acid (PIN)
acetic dicarbonic monoanhydride

The name disulfurous acid should correspond to the structure HO-SO-O-SO-OH implied for all homogeneous diacids in accordance with the definition given in P-67.2. As the reported structure, HO-SO-SO₂-OH, is called ‘disulfurous acid’ in the Nomenclature of Inorganic Chemistry (ref. 12) a different name must be assigned to HO-SO-O-SO-OH. A substitutive name is appropriate in this situation.

Since the name ‘disulfurous acid’ is used for HO-SO-SO2-OH in the Nomenclature of Inorganic Chemistry ref. 12), it cannot be used in the systematic way for HO-SO-O-SO-OH. Accordingly, the preselected name for the latter is ‘1,3-dihydroxy-1λ4,3λ4-dithioxane-1,3-dione’.

Examples:

P-68.0 Introduction
P-68.1 Nomenclature for compounds of the Group 13 elements
P-68.2 Nomenclature for compounds of the Group 14 elements
P-68.3 Nomenclature for compounds of the Group 15 elements
P-68.4 Nomenclature for compounds of the Group 16 elements
P-68.5 Nomenclature for compounds of the Group 17 elements

The nomenclature of organic compounds is based on two approaches. General principles, rules, and conventions applicable, with some rare exceptions, to all compounds of elements belonging to Groups 13 through 17; they have been described and illustrated in previous Chapters. Another approach is based on the identical treatment of compounds within one Group. Up until now the nomenclature of compounds of Group 13 was compounds of the element boron; these will be included in a future publication by another group. It is advantageous to describe all compounds of a Group in the same manner to identify clearly their similarities and underline exceptions, if any. This method should facilitate naming of new compounds by comparison with established models.

Another aspect of nomenclature that is described Group by Group would be to easily grasp the general patterns of the different Groups. The nomenclature of Group 15 is diverse; suffixes are associated with nitrogen, mononuclear and polynuclear acids are the base of many derivatives of phosphorus, arsenic, and many compounds of antimony and bismuth compounds are named substitutively. By comparison, compounds of Group 14 are essentially named by substitutive nomenclature. Thus, the compound C₆H₅-PH-OCH₃ is named by functional class nomenclature as an ester, i.e., methyl phenylphosphinite, but the compound, C₆H₅-SnH(OCH₃)₂ is named substitutively as dimethoxy(phenyl)stannane in spite of their apparent similarity of structures.

There is a third purpose for this Section about Groups 13 through 17. In it, substitutive nomenclature treats metals, semi-metals, and non-metals equally when a compound contains carbon. The Group treatment illustrates many aspects of the nomenclature of organometallic compounds. This is particularly evident for the nomenclature of compounds of the Groups 13 and 14 elements, for which the extensive and well known nomenclature for boron and carbon compounds serves as models to name the other compounds of the Group.

For boron and the metals of Groups 14 and 15, i.e., Ge, Sn, Pb, Sb, and Bi, the same principles are followed as in other sections of these recommendations, namely, if the compound contains carbon and can be named by substitutive nomenclature principles given elsewhere in these recommendations based on acceptable parent hydride names, it is assigned a PIN; however, if there is no carbon present, the name is described as a preselected parent hydride or a name based on a preselected parent hydride or compound. Finally, for many compounds of these elements, their structures are not consistent with the principles of substitutive nomenclature; these, then, are named by the principles of inorganic and coordination nomenclature, for which see ref. 12.

P-68.1 NOMENCLATURE FOR COMPOUNDS OF THE GROUP 13 ELEMENTS

Except for the polynuclear boron hydrides, boron compounds have traditionally been included in the recommendations for naming organic compounds. However, substitutive nomenclature has been applied on the basis of parent hydrides, their substituent groups, and appropriate operations to complement the nomenclature of polynuclear boron compounds, for example names formed by skeletal replacement (‘a’) nomenclature, multiplicative nomenclature, and names derived from the functional parent acids based on boric acid, B(OH)₃, boronic acid, HB(OH)₂, and borinic acid, H₂B(OH); these are retained functional parent compounds.

The nomenclature of Al, Ga, In, and Tl compounds in these recommendations, including formal organometallic compounds, is patterned on boron nomenclature and is recommended only for use in general nomenclature. Recommendations of preferred IUPAC names for most compounds of these elements will appear in a later publication by another group.

P-68.1.1 Parent hydrides
P-68.1.2 Names for substituent groups derived from parent hydrides
P-68.1.3 Modification of the degree of hydrogenation
P-68.1.4 Functional parent compounds
P-68.1.5 Substitutive nomenclature
P-68.1.6 Adducts

P-68.1.1.1 Mononuclear hydrides
P-68.1.1.2 Acyclic polynuclear hydrides
P-68.1.1.3 Cyclic hydrides

The names of the mononuclear hydrides are listed in Table 2.1. The standard bonding number is 3 and the λ-convention (see P-14.1) is used to indicate nonstandard bonding numbers. The names of these parent hydrides are all preselected names (see P-12.2).

Examples:

P-68.1.1.2.1 Acyclic di- and polynuclear parent hydrides are named by citing the number of skeletal atoms in the molecule as a multiplying prefix, ‘di’, ‘tri’, etc., in front of the name of the mononuclear parent hydride. The number of hydrogen atoms in the molecule is designated by an arabic numeral enclosed in parentheses immediately following the name derived as above. These numbers are omitted when there is no ambiguity or by convention in the names of acyclic polynuclear hydrides. A specific nomenclature is used to name polycyclic polyboranes; these names are described in Chapter IR-6.2.3 of ref. 12. Parent hydrides are preselected names.

Examples:

diborane(4) (preselected name)

triborane(5) (preselected name)

diborane(6) (preselected name)

digallane(6) (preselected name)

1-methyldiborane(6) (PIN)

1-carba-nido-pentaborane(5) (PIN)

When nitrogen atoms are present, this is a change from the 1993 Guide (ref. 2) because the ‘amine’ characteristic group was not recognized there.

Examples:

tetramethyldiboroxane (PIN)

trialuminoxane (preselected name)

1-methyl-N-(methylboranyl)boranamine (PIN)

Examples:

2,9-dimethyl-4,7-dioxa-2,9-diboradecane (PIN)
[ethane-1,2-diylbis(oxymethylene)]bis(dimethylborane)

3,5,7-trisila-1,9-diboranonane (PIN)
[silanediylbis(methylene)]bis[(boranylmethyl)silane]
Si,Si′-bis(boranylmethyl)[silanediylbis(methylene)]bis(silane)

P-68.1.1.3.1 Polyhedral polyboranes.

Nomenclature of polyhedral polyboranes constitute a rich and diversified system characterized by specific prefixes. It has been described and illustrated in the Section IR-6.2.3 (ref. 12); it is not reproduced in these recommendations.

Examples:

arachno-tetraborane(10)
(preselected name)

nido-pentaborane(9)
(preselected name)

1,2-dicarba-closo-decaborane(10) (PIN)

Examples:

1,3,6,2-trioxaluminocane
(not 1,3,6-trioxa-2-aluminacyclooctane)

1H-gallole
(not 1-gallacyclopenta-2,4-diene)

1,3,2-dioxaboretane (PIN)
(not 1,3-dioxa-2-boracyclobutane)

1H-borepine (PIN)
(not 1H-1-boracyclohepta-2,4,6-triene)

tetraboretane (preselected name; see P-12.2; P-22.2.5)
cyclotetraborane(4)
(not 1,2,3,4-tetraboracyclobutane)

1,3,2,4-dithiadiboretane (preselected name; see P-12.2; P-22.2.6)
cyclodiborathiane
(not 1,3-dithia-2,4-diboracyclobutane)

1,3,5,2,4,6-triazatriborinane
(preselected name)
borazine (see D-7.54, ref. 1)
cyclotriborazane
(not 1,3,5-triaza-2,4,6-triboracyclohexane)

1,3,5,2,4,6-trioxatriborinane (preselected name)
boroxin (see D-7.54, ref. 1)
cyclotriboroxane
(not 1,3,5-trioxa-2,4,6-triboracyclohexane)

1,3,5,2,4,6-trithiatriborinane (preselected name)
borthiin (see D-7.54, ref. 1)
cyclotriborathiane
(not 1,3,5-trithia-2,4,6-triboracyclohexane)

Examples:

2,5,7,10,11,14-hexaoxa-1,6-diborabicyclo[4.4.4]tetradecane (PIN)

2,4,8,10-tetraoxa-3,9-diboraspiro[5.5]undecane (PIN)

Examples:

boranthrene (PIN)

2-phenyl-2H,4H-[1,3,2]dioxaborolo[4,5-d]imidazole (PIN)

5H-dibenzo[b,d]borole (PIN)

Names of substituent groups –BH₂ and =BH derived from borane are formed by method (2) described in P-29.2; they are preselected prefixes.

Prefixes derived from borane are no longer named by method (1) in P-29.2.

Examples:

Double bonds are denoted by the ‘ene’ ending or by saturation of double bonds of mancude ring systems by the use of ‘hydro’ prefixes, as described in Sections P-31.1 and P-31.2, respectively.

Hydro/dehydro prefixes are now classified as detachable prefixes but are not included in the category of alphabetized detachable prefixes (see P-14.4; see also P-15.1.5.2, P-31.2, P-58.2).

Examples:

triborene(5) (preselected name)

1-methyldecahydro-1-benzaluminine

P-68.1.4.1 The names boric acid, boronic acid, and borinic acid are preselected retained names for the compounds B(OH)₃, HB(OH)₂, and H₂B(OH), respectively (see P-67.1.1). They are preferred IUPAC names for deriving the names of the corresponding salts, esters, or anhydrides; or when the hydrogen atom(s) attached to the boron atom is (are) substituted, for example methylboronic acid for CH₃-B(OH)₂. Chalcogen analogues are named using infixes to denote functional replacement of oxygen by S, Se, and Te.

Acid names such as these are not used for other elements of Group 13, which are named using substitutive nomenclature based on the appropriate parent hydride. For names such as methaneboronic acid vs. methylboronic acid for CH₃-B(OH)₂, see P-67.1.1.2.

Examples:

The general methodology for forming substituent groups derived from the boron acids has been described in P-67.1.4.2. Except for the name ‘borono’ for (HO)₂B– which is retained, their names are formed substitutively based on the parent hydride ‘borane’, BH₃. Chalcogen analogues of ‘borono’ are named by replacement prefixes, and not replacement infixes.

Examples:

Derivatives of borane, BH₃, are named by substitutive nomenclature, the substituents being denoted by suffixes and prefixes in accordance with the principles, rules, and conventions of substitutive nomenclature. The three acids described in P-68.1.4 have retained names that are preselected names.

Derivatives are named in accordance with the seniority of classes described by the general rule in Section P-41. Thus, acids having retained names have seniority over other suffixes. Suffixes are used when recommended in substitutive nomenclature, in accordance with the general rule described in Section P-43. In the absence of a suffix that has priority for naming organic compounds, when a choice is possible for selecting the parent hydride, the seniority order is as follows: N > P > As > Sb > Bi > Si > Ge > Sn > Pb > B > Al > Ga > In > Tl > O > S > Se > Te > C (substituent groups).

P-68.1.5.1 Suffix nomenclature
P-68.1.5.2 Prefix nomenclature

Suffixes, when available, are used to denote characteristic groups; prefixes are not recommended. Suffixes containing a carbon atom generate preferred IUPAC names.

Examples:

P-68.1.5.2.1 Substituted parent hydrides
P-68.1.5.2.2 Compounds with bridging atoms or groups
P-68.1.5.2.3 Compounds with groups of higher seniority

Normal prefix names are used to describe substituents of the B, Al, In, or Tl parent hydrides.

Examples: