Reduction of carboxylic acids with LiAlH4

Steps:

• LiAlH4 is a strong reducing agent that converts carboxylic acids to primary alcohols.
• The -COOH group in CH3COOH is reduced: the carbonyl becomes -CH2OH, retaining the carbon chain.
• Excess LiAlH4 ensures complete reduction, avoiding aldehyde intermediates.
• The product is CH3CH2OH, a one-carbon chain extension from the original acid.

Why A is correct:

• Carboxylic acids (RCOOH) reduce to primary alcohols (RCH2OH) via hydride addition to the carbonyl, as per standard organic reduction rules.

Why the others are wrong:

• B: Ethane-1,2-diol (HOCH2CH2OH) forms from ethylene oxide or oxalic acid reduction, not from acetic acid.
• C: Ethanal (CH3CHO) is an aldehyde intermediate, but excess LiAlH4 reduces it further to alcohol.
• D: Methane (CH4) results from decarboxylation or Clemmensen reduction of ketones, not this reaction.

Final answer: A