Note: Acid hydrolysis of esters to carboxylic acids. More importantly, once you produce and heat a carboxylic acid that is beta to another carbonyl (such as an ester), decarboxylation (loss of CO2) will readily occur via a 6-membered cyclic transition state. The net result of malonic ester synthesis is the apparent alkylation of acetic acid.

Note: Acid hydrolysis of the ester to a carboxylic acid which is beta to the ketone. Under heated conditions, this will readily decarboxylate to yield a net result that is the apparent alkylation of acetone.

Note: Hot acid to yield decarboxylation results in a carboxylic acid substituent on a closed ring.

Note: Sulfonation of benzene is reversible with hot (steaming), dilute acid. This can make it useful as a temporary 'blocking group.'

Note: Aqueous acid may also be used to deprotect silyl ethers

Note: Acetal protecting groups may subsequently be removed by aqueous acid hydrolysis

Note: Acetal protecting groups may subsequently be removed by aqueous acid hydrolysis after the highly reactive organometallic step has been completed

Note: Acid-catalyzed hydrolysis of nitriles to carboxylic acids

Note: Acid-catalyzed hydrolysis of an acetal back to the component carbonyl and alcohols. Excess H₂O is assumed to drive the reaction equilibrium.

Note: Acid-catalyzed hydrolysis of a cyclic acetal back to component molecules

Note: Acid-catalyzed hydrolysis of an imine back to component molecules.

Note: Acid-catalyzed hydrolysis of an enamine back to component molecules.

Note: Carboxylic acids can be prepared from more reactive derivatives like anhydrides by hydrolysis, in this case helped by acid catalysis.

Note: Acid-catalyzed hydrolysis of an ester to a carboxylic acid, with excess water assumed to drive the reaction equilibrium. Virtually all carboxylic acid derivatives can be hydrolyzed to carboxylic acids with aqueous acid.

Note: Amides are among the least reactive carboxylic acid derivatives. One of the few reactions that can be completed is acid-catalyzed hydrolysis

Note: Nitriles are counted among carboxylic acid derivatives in part because they can be hydrolyzed under acid conditions to yield carboxylic acids.

Note: The final step of Gabriel synthesis of a primary amine is hydrolysis of the phthalimide. This is comparable to hydrolysis of an amide to an amine and carboxylic acid.

Note: Treating arenediazonium salts with aqueous acid results in substitution by water. This provides one of the only synthetic methods to produce phenols.

Note: Amino-malonate derived synthesis of amino acids concludes with acid hydrolysis of the amide and esters, including decarboxylation of the resulting beta-di-carboxylic acid.

Note: Hydrolysis of the nitrile yields the carboxylic acid of the amino acid.