Carboxyl

A carboxyl group is a functional group consisting of a carbon atom and an oxygen atom doubly bonded to each other.

Carboxyl groups are characteristic constituents of more complex functional groups such as carboxylic acids, ketones, aldehydes, and amides.

The C=O stretch of carboxyl groups can be identified spectroscopically by a sharp peak in the infrared between 1700 and 2100 cm^-1.