Carboxylic Acids and Derivatives

(See also amides, amidines , etc. under Nitrogen)

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acids: See carboxylic acids, oxoacids, sulfonic acids, etc.

acid anhydrides:*

Compounds consisting of two acyl groups bonded to the same oxygen atom: acyl-O-acyl. Symmetric and mixed anhydrides have identical and different acyl groups, respectively. NOC Rule C-491, GNOC Recom. R-5.7.7. E.g. CH3C(=O)OC(=O)CH3 acetic anhydride, CH 3C(=O)OS(=O)2Ph acetic benzenesulfonic anhydride, PhC(=S)OC(=S)Ph (thiobenzoic) anhydride.

acid thioanhydrides: See thioanhydrides.

acyl anions: See acyl species.

acyl carbenes:

Any compound acyl-C:-R. In organic chemistry, an unspecified acyl carbene is commonly a carboxylic acyl carbene, RC(=O)-C:-R.

acyl cations: See acyl species.

acyl groups:*

Groups formed by removing one or more hydroxy groups from oxoacids that have the general structure RkE(=O)l(OH)m (l not equal to 0), and replacement analogues of such acyl groups. NOC Rules C-403, C-543.3, C-631.1, C-641.7, C-641.8, C-641.9, D-5.67, RNRI Rule RC-81.2.2. E.g. CH 3C(=O)-, CH3C(=NR)-, CH3C(=S)-, PhS(=O)2-, HP([triple bond]N)-, . In organic chemistry an unspecified acyl group is commonly a carboxylic acyl group.

acyl halides:

Compounds consisting of an acyl group bonded to halogen. NOC Rule C-481, GNOC Recom. R-5.7.6. E.g. CH3S(=O)2Cl methanesulfonyl chloride, cyclohexanecarboximidoyl chloride, CH3C(=O)Cl acetyl chloride.

acyl radicals: See acyl species.

acyl species:

Acyl intermediates include acyl anions, acyl radicals and acyl cations (synonym: acylium ions) which are formally derived from oxoacids RkE(=O)l(OH)m (l not equal to 0) by removal of a hydroxyl cation HO+, a hydroxyl radical HO. or a hydroxyl anion HO-, respectively, and replacement analogues of such intermediates. Acyl anions, radicals and cations can formally be represented by canonical forms having a negative charge, an unpaired electron or a positive charge on the acid-generating element of the oxoacid. See under acyl groups.

Acyl anions. E.g. RC-(=O), RS-(=O)2 , RC-(=S), RC-(=NH).

Acyl radicals, RNRI Rule RC-81.2.2. E.g. RC.(=O), RS.(=O)2 .

Acyl cations, RNRI Rule RC- E.g. RC+(=O) [2head arrow] RC[triple bond]O+ .


Diesters of geminal diols; i.e. R2C[OC(=O)R]2. NOC Rule C-332.1, GNOC Recom. E.g. benzylidene diacetate

acylium ions: See acyl species.

acyloxyl radicals:

Oxygen-centered radicals consisting of an acyl radical bonded to an oxygen atom. E.g. RC(=O)O., RC(=NR)O., RS(=O)O..

anhydrides: See acid anhydrides.

carboxylic acids:*

Oxoacids having the structure RC(=O)OH. The term is used as a suffix in systematic name formation to denote the -C(=O)OH group including its carbon atom. NOC Rule C-401.2.

cyclic acid anhydrides/cyclic anhydrides:*

Acid anhydrides derived by loss of water between two oxoacid functions RkE(=O)l(OH)m (l not equal to 0) (carboxylic, sulfonic, etc.) in the same molecule so as to close a ring. NOC Rules C-491.4, C-643.2. Oxo oxygen replacement analogues are included. Cf. thioanhydrides. E.g.


Compounds formally derived from an oxoacid RkE(=O)l(OH)m (l not equal to 0), and an alcohol, phenol, heteroarenol, or enol by linking with formal loss of water from an acidic hydroxy group of the former and a hydroxy group of the latter. By extension acyl derivatives of alcohols, etc. Acyl derivatives of chalcogen analogues of alcohols (thiols, selenols, tellurols) etc. are included. See also acylals, ortho esters, depsides, depsipeptides, glycerides, lactides, lactones, macrolides. NOC Rules C-463, C-464, C-641.5, C-641.6, D-5.61. E.g. R'C(=O)OR, R'C(=S)OR, R'C(=O)SR, R'S(=O)2OR, (HO)2P(=O)OR, (R'S)2C(=O), ROCN (but not R-NCO) (R not equal to H).

Note: O-Alkyl derivatives of other acidic compounds [See amides (1) note] may be named as esters but do not belong to the class esters proper. NOC Rule D-5.21. E.g. (Ph)2POCH3 methyl diphenylphosphinite.


Dialkylidenesuccinic anhydrides (generally photochromic).


Cyclic esters derived by multiple esterification between two (usually) or more molecules of lactic acid or other hydroxy carboxylic acids. They are designated as dilactides, trilactides, etc., according to the number of hydroxy acid residues. NOC Rule C-474.1. E.g. a dilactide (a 1,4-dioxane-2,5-dione)


1. Cyclic hemiacetals formed by intramolecular addition of a hydroxy group to an aldehydic or ketonic carbonyl group. They are thus 1-oxacycloalkan-2-ols or unsaturated analogues. E.g.

2. This term has also been used for hydroxy lactones, but such use is not recommended.


Cyclic esters of hydroxy carboxylic acids , containing a 1-oxacycloalkan-2-one structure, or analogues having unsaturation or heteroatoms replacing one or more carbon atoms of the ring. NOC Rule C-471.1.


Macrocyclic lactones with a ring of twelve or more members.

naphthenic acids:

Acids, chiefly monocarboxylic, derived from naphthenes. The term seems to be obsolescent, except in the petrochemical industry.

ortho acids:*

Hypothetical compounds having the structure RC(OH)3. Thus hydrated forms of carboxylic acids. Orthocarbonic acid, C(OH)4, is generically included. NOC Rule C-464. See also ortho amides, ortho esters.

ortho esters:*

Compounds having the structure RC(OR')3 (R' not equal to H), or the structure C(OR')4 (R' not equal to H). NOC Rule C-464.1. E.g. HC(OCH3)3 trimethyl orthoformate, C(OCH3)4 tetramethyl orthocarbonate.

oxo acids: See oxo carboxylic acids.

oxo carboxylic acids:

Compounds having a carboxy group as well as an aldehydic or ketonic group in the same molecule. NOC Rule C-415. E.g. HC(=O)CH2CH2CH2C(=O)OH 5-oxopentanoic acid. In an organic context the term is generally shortened to oxo acids. The full name should be used if confusion with oxoacids seems possible.

per acids:

An ambiguous term, which may imply either a higher oxidation state of a central atom, as in perchloric acid, or a derivative of hydrogen peroxide, as in CH3C(=O)OOH. Accordingly, it is not recommended as a class name. See peroxy acids.

peroxy acids:*

Acids in which an acidic -OH group has been replaced by an -OOH group. NOC Rule C-441.1. E.g. CH3C(=O)OOH peroxyacetic acid, PhS(=O)2OOH benzeneperoxysulfonic acid.

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