This question involves identifying the correct reducing agent for converting a carboxylic acid to an alcohol. The image shows a carboxylic acid group (R-COOH) being converted to an alcohol (R-CH₂OH).

Step 1: Understand the Reduction Process

Carboxylic acids contain a carbonyl group (C=O) and require strong reducing agents to convert them to primary alcohols. The general reaction is:

$R - COOH \overset{[H]}{\to} R - {CH}_{2} OH$

Step 2: Evaluate Each Option

LiAlH₄ (Lithium aluminium hydride): A strong reducing agent that reduces carboxylic acids to primary alcohols. It is effective for this conversion.

9-BBN (9-Borabicyclo[3.3.1]nonane): A selective reducing agent used for hydroboration of alkenes, not for reducing carboxylic acids.

NaBH₄ (Sodium borohydride): A mild reducing agent that reduces aldehydes and ketones but not carboxylic acids.

All: Since 9BBN and NaBH₄ do not reduce carboxylic acids, this option is incorrect.

Step 3: Final Answer

Only LiAlH₄ is capable of reducing carboxylic acids to primary alcohols. Therefore, the correct answer is LiAlH₄.

Related Topics

Reduction Reactions
Carbonyl Chemistry
Hydride Reducing Agents

Important Formulae and Theory

Reduction of Carboxylic Acid: $RCOOH + 4 [H] \to RCH 2 OH + H_{2} O$

Mechanism: Involves nucleophilic addition of hydride to the carbonyl carbon, followed by elimination and further reduction.

Note: LiAlH₄ provides the necessary hydride ions (H^-) for this reduction, while NaBH₄ is too weak and 9BBN is not suitable.