(1) Carboxylic group (-COOH) in acids is highly polar. in liquid state, pair of carboxylic acid molecules is held together by two intermolecular hydrogen bonds, have higher aggregations and in the vapour.
(2) Intermolecular hydrogen bonding in carboxylic acids state most of the carboxylic acid.s exist as dimmers in which two molecules are held by two hydrogen R – R bonds.
Acidic hydrogen of one molecule forms hydrogen bond with carbonyl oxygen of the other molecule.
This doubles the size of the molecule resulting in increase in o – intermolecular van der Waals forces, which in turn results in high boiling points.
Carboxylic acids possess higher boiling points than those of alcohols, aldehydes, ketones. ether, hydrocarbons of comparable molecular masses.