Carboxylic acid

Structures of three carboxylic acids

Carboxylic acids are important precursor chemicals both in the lab and in living organisms. The twenty common amino acids are a particularly important class of carboxylic acids. Carboxylic acids are generally tart in taste and are thus widely used in the food industry. Foods are often preserved with the addition of sodium benzoate, which is the conjugate base of benzoic aicd. Acetic acid is a carboxylic acid that gives vinegar its bite. Formic acid has historically been used to preserve specimens of animal tissue.

chemical properties

Carboxylic acids contain a carbon atom that is attached to one oxygen with a double bond, a hydroxyl group by a single bond, and one additional bond to an organic group, often an alkane or alkene group. Carboxylic acids are weak acids, in the Brønstad-Lowry sense, with pKa's around 4.5. Carboxylic acids can be formed by the hydrolyses of a corresponding ester. Thus, ethyl acetate can be hydrolyzed to from acetic acid and ethanol. Conversely, the Fisher esterification reaction can be used to react a carboxylic acid with an alcohol to form an ester. Carboxylic acids can also be reduced to form aldehydes or further reduced to form primary alcohols.

flavoring agents

Their tart taste makes many carboxylic acids useful as flavoring agents in the food industry. Citrus acid is widely used in fruit punches and candy.