Reduction of carboxylic acids with LiAlH4 yields primary alcohols

Steps:

• Identify the reactant: ethanoic acid (CH3COOH) contains a carboxylic acid group (-COOH).
• Recall the reaction: LiAlH4 reduces carboxylic acids to primary alcohols by converting -COOH to -CH2OH.
• Apply to structure: the carbonyl carbon in CH3COOH gains two hydrogens, forming CH3CH2OH.
• Confirm excess reagent ensures complete reduction to alcohol, not intermediate.

Why A is correct:

• LiAlH4 fully reduces RCOOH to RCH2OH, so CH3COOH yields CH3CH2OH (ethanol) per standard organic reduction mechanism.

Why the others are wrong:

• B: Ethane-1,2-diol (HOCH2CH2OH) forms from ethylene oxide or oxalate reduction, not carboxylic acids.
• C: Ethanal (CH3CHO) is an aldehyde intermediate, but LiAlH4 over-reduces it to alcohol.
• D: Methane (CH4) results from decarboxylation or unrelated reactions, not LiAlH4 reduction.

Final answer: A