International Union of Pure and Applied Chemistry

Division VIII Chemical Nomenclature and Structure Representation Division

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

Prepared for publication by Henri A. Favre and Warren H. Powell, Royal Society of Chemistry, ISBN 978-0-85404-182-4

Changes to the web Blue Book made since first made public on 17 May 2021.

P-12.1, paragraph before example 6. [corrected 26 January 2022]
For ...substitutive names ‘vinylbenzene’, ‘phenylethene’, and ‘phenylethylene’. The name...
read ...substitutive name ‘vinylbenzene’. The name...

P-12.1, example 6. [corrected 26 January 2022]
Delete phenylethene and phenylethylene

P- [corrected 16 June 2021]
Add after example 8
1H-tetrazole (PIN)
(not 1H-1,2,3,4-tetrazole)

P-, example 2. [modified 16 June 2021]
For (not 4-chorotrioxetane)
read (not 4-chloro-1,2,3-trioxetane)

P-14.6, example 3. [modified 23 February 2022)
For N-{2-[(acetyldimethylsilyl)methoxy]ethyl}-N-[2-({2-[(2-aminoethyl)amino]ethyl}amino)ethyl]ethane-1,2-diamine
read N1-{2-[(acetyldimethylsilyl)methoxy]ethyl}-N2-[2-({2-[(2-aminoethyl)amino]ethyl}amino)ethyl]ethane-1,2-diamine

for N-[2-({2-[(acetyldimethylsilyl)methoxy]ethyl}amino)ethyl]-N-{2-[(2- aminoethyl)amino]ethyl}ethane-1,2-diamine
read N1-[2-({2-[(acetyldimethylsilyl)methoxy]ethyl}amino)ethyl]-N2-{2-[(2- aminoethyl)amino]ethyl}ethane-1,2-diamine

P-, line 2. [corrected 26 January 2022]
For ...For example, in a cyclic unsaturated alcohol having one substituent group...
read ...For example, in an unsaturated alcohol having one substituent group...

P-, example 2. [corrected 10 June 2021]
For (not N-nitrosoaniline)
read N-nitrosoaniline

P-, example 6. [corrected 10 June 2021]
For ethyl(methyl)(propyl)silanecarboxylic acid
read ethyl(methyl)(propyl)silanecarboxylic acid PIN)

P-, example 7. [corrected 10 June 2021]
For methyl(phenyl)phosphinic acid
read methyl(phenyl)phosphinic acid PIN)

P-, example 8. [corrected 10 June 2021]
For cyclopropyl(phenyl)methanol
read cyclopropyl(phenyl)methanol PIN)

P-, example 1. [corrected 10 June 2021]
For bromo(nitro)(phenyl)acetic acid
read bromo(nitro)(phenyl)acetic acid PIN)

P-, example 2. [corrected 10 June 2021]
For diethyl ethyl(methyl)propanedioate
read diethyl ethyl(methyl)propanedioate PIN)

P-, example 3. [corrected 10 June 2021]
For bromo(chloro)acetic acid
read bromo(chloro)acetic acid PIN)

P-, example 4. [corrected 10 June 2021]
For cyclopropyl(fluoro)acetonitrile
read cyclopropyl(fluoro)acetonitrile PIN)

P- [corrected 30 March 2022]
Replace section (retain box at end)

P- The presence of square brackets and/or parentheses that are an integral part of the name of a parent structure may affect the nesting order as described below.

P- In determining the nesting order in a name the parentheses of added indicated hydrogen are ignored.


1-(3,4-dihydroquinolin-1(2H)-yl)ethan-1-one (PIN, P-64.3.2)

P- In determining the nesting order in a name the square brackets of ring fusion, spiro fusion, ring assembly, or the extended von Baeyer names are ignored.


(7,7-dimethyl-2-oxobicyclo[2.2.1]heptan-1-yl)methanesufonic acid (PIN, P-14.8.1)
10,10′-[[1,1′-biphenyl]-4,4′-diylbis(oxy)]didecanoic acid (PIN, P-
trispiro[1-oxaspiro[2.3]hexane-2,3′:4,3′′:5,3′′′-tri(tetracyclo[,7.04.6]heptane)] (PIN, P-
N-(dibenzo[b,d]furan-1-yl)acetamide (PIN, P-

P- In determining the nesting order in a name the parentheses used to indicate compound locants, phane amplifiction locants, stereochemistry, specific isotopic substitution, or coordination with multicenter bonding are taken into consideration.


2-[bicyclo[6.6.1]pentadeca-8(15)-en-1-yl]ethan-1-ol (PIN)
trimethyl[12H-1(6)-pyrana-3,5(1,4),7(1)-tribenzenaheptaphan-74-yl]silane (PIN) (P-
[1(1′)E,3E,3′E-3,3′-diethylidene-1,1′-bi(cyclobutylidene) (PIN, P-
[1(44)E,2S,26R]-bicyclo[24.20.1]heptatetraconta-1(46),44,45-trien-2-ol (PIN, P-
10-{[(3S)-1-phosphabicyclo[2.2.2]octan-3-yl]methyl}-10H-phenoxazine (PIN)
(3S)-2-[(2S)-2-{[(1S)-1-ethoxy-1-oxo-4-phenylbutan-2-yl]amino}propanoyl]-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid (PIN)
1,2-di[(13C)methyl]benzene (PIN. P-82.2.1)
3-[ethyl(2-34S)trisulfanyl]propanoic acid (PIN, P-
[(2,3,5,6-η)-bicyclo[2.2.1]hepta-2,5-diene]tricarbonyliron (P-69.2.4)
{μ-[2(1-3,3a,8a-η):1(4-6-η)]azulene}-(pentacarbonyl-1κ3C,2κ2C)diiron(Fe—Fe) (P-69.2.5)

P- In determining the nesting order where square brackets are used for an isotopically labelled compound, by convention, parenthesis are used.


1-(amino[14C]methyl)cyclopentan-1-ol (PIN, P-

P- When the nesting order given in P-16.5.4 results in consecutive enclosing marks of the same level, the next level of enclosing mark is used. For example the following name formed by the application of the nesting order rules given above results in the appearance of consecutive parentheses twice.

2-{2-[(1-ethoxy-1-oxo-4-phenylbutan-2-yl)amino]propanoyl}-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid (without stereochemistry)
(3S)-2-[(2S)-2-{[(2S)-1-ethoxy-1-oxo-4-phenylbutan-2-yl]amino}propanoyl]-1,2,3,4-tetrahydroisoquinoline-3-carboxylic (with stereochemistry)

With this example the stereochemistry needs to be inserted at three positions. Insertion of the third one into the name without stereochemistry results in two opening parenthesis next to each other. Hence to clarify the brackets these need to be adjusted as shown by the second name.

Explanation: The order of insertion of stereochemistry for 2-{2-[(1-ethoxy-1-oxo-4-phenylbutan-2-yl)amino]propanoyl}-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid is as shown below.

Stage 1 insert stereochemistry at the inner most position:

2-{2-{[(2S)-1-ethoxy-1-oxo-4-phenylbutan-2-yl]amino}propanoyl}-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid

The substituent (2S)-1-ethoxy-1-oxo-4-phenylbutan-2-yl requires square brackets to surround it hence subsequent enclosing marks need to be adjusted.

Stage 2 insert stereochemistry at the next position:

2-[(2S)-2-{[(2S)-1-ethoxy-1-oxo-4-phenylbutan-2-yl]amino}propanoyl]-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid

The substituent (2S)-2-{[(2S)-1-ethoxy-1-oxo-4-phenylbutan-2-yl]amino}propanoyl has a parenthesis on the left and brace on the right so to make clear it requires square brackets around it.

Stage 3 insert stereochemistry at the third position:

(3S)-2-[(2S)-2-{[(2S)-1-ethoxy-1-oxo-4-phenylbutan-2-yl]amino}propanoyl]-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid

P-16.5, contents list. [corrected 30 March 2022]
Add P-16.5.4 Multiple enclosing marks

P-16.5.4.. [corrected 30 March 2022]
For P-16.5.4 When multiple types...
read P-16.5.4 Multiple enclosing marks

When multiple types...

After P- [corrected 16 June 2021]
P- Omission of locants

All locants are omitted for parent Hantzsch-Widman names if there is only one heteroatom or if there is no ambiguity if locants are omitted.


(not 1-thiepine)

(not 1H-1,2,3,4-tetrazole)

P-, example 1. [corrected 26 January 2022]
Delete 3-benzooxepine

P-, example 2. [corrected 26 January 2022]
Delete 4H-3,1-benzooxazine

P- [1 December 2021]
For ...horizontal rows. Such rows...
read ...horizontal rows. If the compound requires distorted rings not shown above see P- Such rows...

P-, before the example add. [corrected 23 February 2022)

P- [corrected 1 December 2021]
For P-
read P-

P- Distorted ring shapes
If a compound cannot be drawn only using the shapes shown in P- a distorted ring shape will be required. The distorted ring should be as small as possible.

only preferred shapes used distorted five-membered ring
only preferred shapes used
(the separation to show the
seven-membered ring is not
fused to the left hand ring
does not count as a distortion)
 distorted seven-membered ring
distorted four-membered ring distorted six-membered ring

P-, replace the structure of example 1. [corrected 26 January 2022]

P-, replace structure of example 2. [corrected 26 January 2022]

P-, replace structure of example 2 on this page. [corrected 26 January 2022]

P-25.8.1, Note 3. [modified 11 August 2021]
For In the order of seniority used by CAS quinolizine precedes quinoline and the indacenes precede biphenylene.
read In the order of seniority used by CAS quinolizine precedes quinoline and isoquinoline; and indolizine preceeds indole and isoindole.

P-, example 2. [corrected 30 March 2022]
For Step 2: 14,2,4,514,6,12-hexaoxa-114,54-dithia-3(2,5)-furana-1,5(1,5)dicyclotetradecanacyclododecaphane (I) (PIN)
read Step 2: 14,2,4,514,6,12-hexaoxa-114,54-dithia-3(2,5)-furana-1,5(1,5)-dicyclotetradecanacyclododecaphane (I) (PIN)

P-28.2.3. [corrected 1 December 2021]
For bivalent
read divalent

P-28.5, example 3. [corrected 30 March 2022]
For 11H,21H,31H,41H,51H,61H,71H-1,7(2),2,3,4,5,6(2,5)heptapyrrolaheptaphane (PIN)
read 11H,21H,31H,41H,51H,61H,71H-1,7(2),2,3,4,5,6(2,5)-heptapyrrolaheptaphane (PIN)

P-31.0, line 4. [corrected 26 January 2022]
For ...also called ‘mancude’ compounds (an acronym for MAximum Number of nonCUmulated DoublE bonds)....
read ...also called ‘mancude’ compounds (an acronym for MAximum number of NonCUmulated DoublE bonds)....

P-45.4.2 (formerly P-45.4.5), example. [corrected 30 March 2022]
For 2-[(13C)methyloxy]-N-{2-[methyl(18O)oxy]ethyl}ethan-1-amine (PIN)
read 2-(13C)methoxy-N-[2-(18O)methoxyethyl]ethan-1-amine (PIN)

for [not 2-[methyl(18O)oxy]-N-{2-[(13C)methyloxy]ethyl}ethan-1-amine]
read [not 2-(18O)methoxy-N-[2-(13C)methoxyethyl]ethan-1-amine]

P-45.4.3 (formerly P-45.4.6), [was a new example]. [corrected 30 March 2022]
For 4-([2-13C]ethyl)-2-[2-([2-14C]ethyl)pentyl]heptan-1-ol (PIN)
read 4-[2-13C]ethyl-2-(2-[2-14C]ethylpentyl)heptan-1-ol (PIN)

for [not 4-([2-14C]ethyl)-2-[2-([2-13C]ethyl)pentyl]heptan-1-ol
read [not 4-[2-14C]ethyl-2-(2-[2-13C]ethylpentyl)heptan-1-ol

P-57.4, example 4, explanation, line 1. [corrected 26 January 2022]
For ...involves a choice is between a ‘methyl’ group...
read ...involves a choice between a ‘methyl’ group...

P-, example 4. [corrected 26 May 2021]
For 1H,2H-3a,7a-methano[2]benzofuran (PIN)
read 1H,2H-3a,7a-methano-2-benzofuran (PIN)

P-62.1 (a) (2), lines 1/2. [corrected 26 January 2022]
For ...compounds having the structure R-N=CR2 (R = H or hydrocarbyl),...
read ...compounds having the structure R2C=N-R (R = H or hydrocarbyl),....

P-, Note line 5. [corrected 26 January 2022]
For ...functional class name were eliminated to form...
read ...functional class name is eliminated to form...

P-, example 8. [corrected 26 January 2022]
For N-cyclopropylbutan-1-amine
read (not N-cyclopropylbutan-1-amine)

P-, example 1. [corrected 23 February 2022)
Replace structure by

P-62.6.1 (1), line 2. [corrected 26 January 2022]
For ...the terminal letter, ‘e’ if present...
read ...the terminal letter ‘e’, if present...

P-, lines 2/3. [corrected 26 January 2022]
For ...lower than ‘ketone’. It is the stereospecific trans- or (E)- stereoisomer.
read ...lower than ‘ketone’. Chalcone refers only to the trans- or (E)- stereoisomer.

P-, example 5. [modified 26 January 2022]
For benzal
read [not benzil]

P-, line 1. [corrected 26 January 2022]
For Only the following five retained names are preferred IUPAC names....
read Only the following five carboxylic acids are retained names and are also preferred IUPAC names.....

P-65.5.4 (2) [corrected 1 December 2021]
For bivalent
read divalent

P-, replace structure of example 9. [corrected 26 January 2022]

P-, example 3. [corrected 16 June 2021]
For P,P′-diacetic P,P′-dipropanoic ethane-1,2-diylbis(phosphonic) tetraanhydride (PIN)
read P,P′-diacetic P,P′-dipropanoic (ethane-1,2-diyl)bis(phosphonic) tetraanhydride (PIN)

P-66 title. [corrected 26 January 2022]

P-66.1.0, lines 3-5. [corrected 26 January 2022]
For ...three acyl groups on a single nitrogen atom are generically included and may be designated as primary, secondary, and tertiary amides, respectively.
read ...three acyl groups on a single nitrogen atom are generically included.

P-, example 1. [corrected 26 January 2022]
For N,N-dimethylformamide (PIN)
read dimethylformamide (PIN)

Delete dimethylformamide

P-, line 1. [corrected 26 January 2022]
For ... H2N-CO-NH2 has the retained named ‘urea’, which...
read ... H2N-CO-NH2 has the retained name ‘urea’, which...

P-, example 1. [corrected 23 February 2022)
For N-(propan-2-yl)dicarbonic diamide (PIN)
read N1-(propan-2-yl)dicarbonic diamide (PIN)

P-, example 3. [corrected 30 March 2022]
For [2-(1,3-dioxolan-2-yl)ethyl]trimethylsilane (PIN)
read [2-(1,3-dioxolan-2-yl)ethyl]tri(methyl)silane (PIN)

P-, example 1. [corrected 30 March 2022]
For bromo(chloro)phenylborane (PIN)
read bromo(chloro)(phenyl)borane (PIN)

P-, example 10. [corrected 30 Mach 2022]
For (difluoroboranyl)trimethylsilane (PIN)
read (difluoroboranyl)tri(methyl)silane (PIN)

P- (formerly P-, example 2 on his page. [modified 23 February 2022)
Replace structure by

for N,N-bis({3,5-di-tert-butyl-2-[(diethylgallanyl)oxy]phenyl}methylidene)-2(NGa)-ethane-1,2-diamine
read N1,N2-bis({3,5-di-tert-butyl-2-[(diethylgallanyl)oxy]phenyl}methylidene)-2(NGa)-ethane-1,2-diamine

for (μ-{2,2′-[ethane-1,2-diylbis(azanylylidene-1κN:2κN-methanylylidene)bis(4,6-di-tert-butylphenolato-1κO:2κO′)di(ethanido-1κ2C1,2κ2C1)gallium
read (μ-{2,2′-[ethane-1,2-diylbis(azanylylidene-1κN1:2κN2-methanylylidene)bis(4,6-di-tert-butylphenolato-1κO:2κO′)bis[di(ethanido-1κ2C1,2κ2C1)gallium]

P-, example 1. [modified 30 March 2022]
For (1) (anthracen-2-yl)diazenyl]naphthalen-2-yl}phenyldiazene (PIN)
read (1) {7-[(anthracen-2-yl)diazenyl]naphthalen-2-yl}(phenyl)diazene (PIN)

for {not [7-(anthracen-2-yldiazenyl)naphthalen-2-yl]phenyldiazene
(numbering shown); alphanumerical order ‘anthracen-2-yl’ precedes ‘anthracen-2-yldiazenyl’}
read {not (anthracen-2-yl)[7-(phenyldiazenyl)naphthalen-2-yl]diazene;
each primary substituent has the same locant, i.e., none, so ‘anthracenyldiazenyl’ is alphabtically preferred to ‘anthracenylphenyl’}

P-73.4, example 2. [corrected 30 March 2022]
For 2-ethoxy-N-{2-[(2-ethoxyethyl)methylsulfaniumyl]ethyl}-N,N-dimethylethanaminium (PIN)
read 2-ethoxy-N-{2-[(2-ethoxyethyl)(methyl)sulfaniumyl]ethyl}-N,N-dimethylethanaminium (PIN)

P-82.2.5, example 1. [corrected 1 December 2021
Delete acet(2H)amide

P-82.6.2, example 3. [corrected 1 December 2021
Delete D-(O-2H)glycer(2H)aldehyde

P- was P- [corrected 1 December 2021
For P-
read P-

Insert new P- after P- [corrected 1 December 2021

P- When the nuclide is located at a position in a retained name that is not numbered a systematic name that identifies separately the relevant atom is used for the IUPAC preferred name. For general nomenclature an italicized prefixes or Greek letters may be used to denote its position.

benzene(13C)carbonitrile (PIN)

benzene(13C)carboxylic acid (PIN)
(carboxyl-13C)benzoic acid

[benzene[14C]carbonyl]phosphonic acid (PIN)
[phenyl[14C]carbonyl]phosphonic acid
[carbonyl-14C]benzoylphosphonic acid

[phenyl(13C)methyl]hydrazine (PIN)

P-, example 8 on this page [modified 30 March 2022]
For O-ethyl 18O-methyl naphthalene-2-yl[18O]phosphonate (PIN)
read O-ethyl 18O-methyl (naphthalene-2-yl)[18O]phosphonate (PIN)

For ...(see P-
read ...(see P-

P-93.2.3, example 1. [corrected 10 June 2021]
Add [(S)-ethyl(methyl)(phenyl)azaniumyl]oxidanide

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