Which functional group is primarily responsible for the acidity of carboxylic acids?

The acidity of carboxylic acids is primarily attributed to the presence of the carboxyl group, which is written as –COOH. This functional group consists of both a carbonyl (C=O) and a hydroxyl (–OH) group. In carboxylic acids, the hydrogen atom in the hydroxyl part of the carboxyl group can dissociate as a proton (H+), which leads to the characteristic acidic behavior of these compounds.

When a carboxylic acid donates a proton, it forms a carboxylate ion (RCOO–). The stability of this ion is enhanced due to resonance stabilization, as the negative charge can be delocalized across the two oxygen atoms. This ability to stabilize the negative charge contributes significantly to the acidity of carboxylic acids compared to other functional groups.

Other groups listed, such as the hydroxyl group, amino group, and carbonyl group, do not confer the same level of acidity. While hydroxyl groups can also participate in hydrogen bonding and may display some acidic properties, they lack the resonance stabilization seen in carboxyl groups once they lose a proton. Thus, the defining feature of carboxylic acids and their acidity is indeed