Carboxylic acids with alpha-hydrogens undergo halogenation at the alpha-position using chlorine or bromine in the presence of red phosphorus, a reaction known as Hell-Volhard-Zelinsky reaction.

Sodium borohydride is ineffective in reducing the carboxyl group in carboxylic acids. Diborane is preferred for reduction as it selectively targets the carboxyl group without affecting other functional groups like ester, nitro, or halo groups.

Carboxylic acids undergo decarboxylation, losing carbon dioxide, when heated with sodalime (NaOH and CaO). Kolbe electrolysis involves the decarboxylation of alkali metal salts of carboxylic acids during electrolysis, resulting in hydrocarbons with twice the carbon atoms in the alkyl group.

Carboxylic acids can be reduced to primary alcohols using lithium aluminium hydride or diborane. Diborane is preferable as it avoids reduction of other functional groups.

Direct attachment of groups like phenyl or vinyl increases the acidity of carboxylic acids, contrary to the expected decrease due to resonance effects. This is attributed to the greater electronegativity of the sp² hybridized carbon to which the carboxyl carbon ...