Oxidation–Reduction Reactions
In hydration reactions, water adds to a carbonyl, forming a geminal diol.
When one equivalent of alcohol reacts with an aldehyde (via nucleophilic addition), a
hemiacetal is formed. When the same reaction occurs with a ketone, a hemiketal is formed.
When another equivalent of alcohol reacts with a hemiacetal (via nucleophilic substitution), an
acetal is formed. When the same reaction occurs with a hemiketal, a ketal is formed.
Nitrogen and nitrogen derivatives react with carbonyls to form imines, oximes, hydrazones, and
semicarbazones. Imines can tautomerize to form enamines.
Hydrogen cyanide reacts with carbonyls to form cyanohydrins.
Aldehydes can be oxidized to carboxylic acids using an oxidizing agent like KMnO 4 , CrO 3 , Ag 2 O, or
H 2 O 2 . They can be reduced to primary alcohols via hydride reagents (LiAlH 4 , NaBH 4 ).
Ketones cannot be further oxidized, but can be reduced to secondary alcohols using the same
hydride reagents.
