Carboxylic Acids Carboxylic Acids Carboxylic acids are important members of the class of compounds in which an OH group is bonded to carbon. The feature that differentiates the carboxylic acids from the alcohols is that the carbon attached to the OH also has a doubly bonded oxygen. CH 3 CO 2 H. Acetic acid is formed by the oxidation of ethanol and is responsible for the sour flavor of a spoiled bottle of wine. The C 6 H 5 group is a benzene ring, so this compound simply has an acid group attached to a benzene ring.
Benzoic acid is a common food preservative.