IUPAC names carboxylic acids by replacing the ending -e of the alkane with the same number of carbons with -oic .

carboxylic acid nomenclature

[1] Methanoic acid (Formic acid)

[2] Ethanoic acid (Acetic acid)

[3] Propanoic acid (Propionic acid)

[4] Butanoic acid (Butyric acid)

When the acid has substituents, the longest chain is numbered by giving the lowest locant to the carbon of the acid group. Carboxylic acids have priority over other groups, which are named as substituents.

2 carboxylic acid nomenclature

[5] 4-Hydroxy-3-methylpentanoic acid

[6] 2-Bromo-5-oxoheptanoic acid

Carboxylic acids also have priority over alkenes and alkynes. Molecules with two acid groups are named with the ending -dioic .


3 carboxylic acid nomenclature

[7] Hex-4-enoic acid

[8] Pentanedioic acid

[9]  But-3-ynoic acid

When the acid group is attached to a ring, the cycle is taken as the main chain and ends in


carboxylic acid nomenclature

[10] Cyclohexanecarboxylic acid

[11] 3-Methylcyclohexanecarboxylic acid