NaBH4 Reduces Aldehydes and Ketones to Alcohols

Steps:

• Identify functional groups in compound Z; assume it contains a carbonyl (aldehyde or ketone) based on typical problems.
• NaBH4 selectively reduces aldehydes/ketones to primary/secondary alcohols without affecting other groups like carboxylic acids.
• With excess NaBH4, all reducible carbonyls convert to alcohols.
• The product structure shows the carbonyl replaced by CH(OH) or CH2OH.

Why A is correct:

• A depicts the alcohol from carbonyl reduction, matching NaBH4's action on C=O to C-OH per the reduction mechanism.

Why the others are wrong:

• B shows unreduced carbonyl, ignoring NaBH4's reactivity.
• C indicates ester reduction, but NaBH4 does not reduce esters under standard conditions.
• D suggests carboxylic acid formation, which NaBH4 cannot produce from ketones/aldehydes.

Final answer: A