Doc: Nomenclature of Carboxylic Acids

Functional Group

• Carboxyl group: -COOH or -CO₂H

• The carboxyl group (-COOH) has the highest priority among all functional groups in IUPAC nomenclature.

• When present in a compound, it is always treated as the principal functional group, and the suffix -oic acid (or -dioic acid for two groups) is used in the name.

• Other functional groups are named as substituents using their prefix forms (e.g., hydroxy-, amino-, oxo-, etc.).

Basic IUPAC rules for naming carboxylic acids

(A) Identify the Parent Chain

• Choose the longest carbon chain containing -COOH.

• This chain becomes the parent hydrocarbon.

• Carbon of -COOH is always C-1, while we use arabic numerals only when needed to indicate positions of other substituents.

(B) Suffix

Replace the terminal -e of the alkane with -oic acid.
Examples

1. CH₃COOH → ethane → ethanoic acid

2. CH₃CH₂CH₂COOH → butane → butanoic acid

(C) Multiple -COOH Groups

If there are two or more carboxyl groups, indicate this by the suffix -dioic acid, -trioic acid, etc., and give appropriate locants. Use prefixes di-, tri-, tetra-etc.

Examples

• HOOC-CH₂-COOH → propanedioic acid (malonic acid)

• HOOC-(CH₂)₂-COOH → butanedioic acid (succinic acid)

(D) Substituents

Name other substituents (alkyl, halo, nitro, amino, oxo, etc.) and give their positions using Arabic numerals. Use hyphens to separate numbers and words, and commas to separate multiple numbers.

Common substituents:

• alkyl (methyl, ethyl...)

• halo (chloro, bromo...)

• nitro (NO₂)

• amino (NH₂)

• hydroxy (OH)

• oxo (=O)

Example:

• 3-oxo-2-methylbutanoic acid

Table - 1 : IUPAC Nomenclature of Acid derivatives :-

S.No.	Compound	IUPAC Name
1		Methanoic acid
2		Ethanoic acid
3		2-Cyclohexylpropanoic acid
4		3-Oxo-2-propylbutanoic acid
5		4-Aminobutanoic acid
6		3-Phenylpentanoic acid
7		3-Methylbutanoic acid
8		Ethanoyl chloride
9		Propanoyl chloride
10		3-Bromobutanoyl bromide
11		Cyclopentanecarbonyl chloride
12		Ethanoic anhydride
13		Trifluoroethanoic anhydride
14		1,2-Benzenedicarboxylic anhydride (common name: phthalic anhydride)

S.No.	Compound	IUPAC Name
1		Methanoic acid
2		Ethanoic acid
3		2-Cyclohexylpropanoic acid
4		3-Oxo-2-propylbutanoic acid
5		4-Aminobutanoic acid
6		3-Phenylpentanoic acid
7		3-Methylbutanoic acid
8		Ethanoyl chloride
9		Propanoyl chloride
10		3-Bromobutanoyl bromide
11		Cyclopentanecarbonyl chloride
12		Ethanoic anhydride
13		Trifluoroethanoic anhydride
14		1,2-Benzenedicarboxylic anhydride (common name: phthalic anhydride)

Dicarboxylic Acids

If the substituent is a second carboxyl group, we have a dicarboxylic acid. For example :

Oxalic acid or Ethanedioic acid                               

 Malonic acid -1, 3- dioic acid      

 Succinic acid -1, 4- dioic acid

Glutaric acid

Adipic acid - hexane-1,6-dioic acid

Pimelic acid - heptane-1,7-dioic acid

Malonic acid - Propanedioic acid    

Succinic acid - Butanedioic acid    

Adipic acid - Hexanedioic acid