Concept:

Lithium aluminum hydride (\(\text{LiAlH}_4\)) is an extremely powerful reducing agent capable of fully reducing carbonyl and carboxyl groups down to the lowest oxygenated state.

Formula:

$$ \text{CH}_3\text{COOH} \xrightarrow{\text{1. LiAlH}_4, \text{ether} / \text{2. H}_3\text{O}^+} \text{CH}_3\text{CH}_2\text{OH} $$

Solution:

• Acetic acid (a 2-carbon carboxylic acid) undergoes vigorous reduction when treated with \(\text{LiAlH}_4\).



• It does not stop at the intermediate aldehyde stage because \(\text{LiAlH}_4\) is too reactive.



• It fully reduces the carboxyl group to a primary alcohol.



• The 2-carbon primary alcohol is ethanol.

Why other options are incorrect:

Ethanal (an aldehyde) is the intermediate but cannot be isolated using \(\text{LiAlH}_4\). Ethanoic is just the IUPAC name for the reactant itself. Ethane would require complete deoxygenation (like red P/HI), which \(\text{LiAlH}_4\) cannot achieve for acids.