Britannica Sources used in this answer

Why does formic acid boil at a higher temperature than ethanol?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

oxidation of alcohols — carboxylic acid Alcohols may be oxidized to give aldehydes, ketones, and carboxylic acids. The oxidation of organic compounds generally increases the number of bonds from carbon to oxygen, and it may decrease the number of bonds to hydrogen.

Formic acid boils at a higher temperature than ethanol primarily because of the way their molecules interact through hydrogen bonding.1

Although both compounds have nearly identical molecular weights, two molecules of a carboxylic acid can form two hydrogen bonds with each other, whereas two alcohol molecules can only form one. This allows carboxylic acids to exist as dimers—pairs of molecules—in both the liquid and, to some extent, the gaseous state.1

Because of this dimerization, boiling a carboxylic acid requires more energy for two reasons:
* If the dimer persists into the gaseous state, the effective molecular weight is doubled.1
* If the dimer is broken during the phase change, additional energy is required to overcome the two hydrogen bonds.1

Consequently, the stronger intermolecular attraction in formic acid necessitates a higher temperature to reach the boiling point compared to ethanol.1