Test: Reactions of Aldehydes & Ketones(9 Dec) - JEE MCQ

NaBH₄ brings about reduction of carbonyls by hydrid e transfer mechanism at planar sp² carbon. Hence, if a chiral carbon is generated, racemic mixture is always produced.

LiAIH₄ reduces both carbonyls and carboxylic groups but does not reduce olefinic bond.

In the above reaction, four stereoisomers, two pairs of enantiomers are formed. Each member of a pair of enantiomer is diastereomer of each member of other pair of enantiomer. Hence, fractional crystallisation would give two fractions, each containing racemic mixture.

Clemmensen reduction is suitable for reductio n of carbonyls containing additional acidic functional group.

Wolff-Kishner reduction is suitable for reduction of carbonyls containing olefinic bonds. If Clemmensen reduction is done, HCI also attacks olefinic bonds.

With aluminium isopropoxide (MPV reduction), carbonyls are selectively reduced to alcohols leaving other groups intact.

If possible, intramolecular reaction is preferred over intermolecular reaction.

In MPV reduction, carbonyl is reduced to alcohol while isopropoxide fraction of reducing agent is oxidised to acetone.