protects has specified product has specified reactant has_intermediate carbonyl group alcohol hemiacetal acetal carbonyl group protection acetal protection 2021-05-17T09:38:59Z RXNO RXNO:0000658 The acid-catalyzed formation of an acetal (or ketal) to protect a carbonyl group by nucleophilic addition of an alcohol to an aldehyde (or ketone) with the elimination of water. acetalisation acetalization