Q.Explain why formic acid ($\text{HCOOH}$, boiling point $100.5\,^\circ\text{C}$) boils at a distinctly higher temperature than an alcohol of comparable molar mass, using the concept of carboxylic-acid dimerisation.

Formic acid's $\text{-COOH}$ group can both donate a hydrogen bond (via its $\text{-OH}$) and accept one (via its carbonyl oxygen); two molecules exploit both capabilities at once, pairing up into a closed, ring-shaped dimer in which each molecule simultaneously donates a hydrogen bond to the other and accepts one back -- a structure held together by two hydrogen bonds, not one. This dimer persists strongly even in the vapour phase and in non-polar solvents. For boiling-point purposes, the dimer behaves as though it were a single, much heavier particle, and two hydrogen bonds -- not just one -- must be broken before the pair can separate and vaporise as individual molecules, both of which raise the boiling point well above what …

Identify that a carboxylic acid, unlike an alcohol, can both donate AND accept a hydrogen bond simultaneously, allowing a doubly hydrogen-bonded cyclic dimer to form -- …

Attributing the high boiling point only to 'the carboxyl group being polar' -- polarity alone gives only ordinary dipole-dipole attraction; the DISTINCTIVE extra boiling-point boost specifically comes from the doubly hydrogen-bonded CYCLIC …