Question

The reagent which can do the conversion CH₃COOH → CH₃ - CH₂ - OH is

• A. LiAlH₄ / ether
• B. H₂, Pt
• C. NaBH₄
• D. Na and C₂H₅OH

Answer 1

The Correct Option is A

To solve the problem, we need to identify the reagent that can convert CH₃COOH (acetic acid) to CH₃-CH₂-OH (ethanol).

1. Understanding the Reaction:
The starting compound, CH₃COOH, is a carboxylic acid (acetic acid), and the product, CH₃-CH₂-OH, is a primary alcohol (ethanol). This conversion involves reducing the carboxylic acid to its corresponding alcohol, which means reducing the -COOH group to -CH₂OH. Ethanol has two carbons, matching acetic acid, so this is a straightforward reduction.

2. Analyzing the Reduction of Carboxylic Acids:
Carboxylic acids are relatively stable and require strong reducing agents to be converted to alcohols. Common reagents for this reduction include:
- LiAlH₄ (lithium aluminum hydride), a strong reducing agent that can reduce carboxylic acids to primary alcohols.
- NaBH₄ (sodium borohydride), which is milder and typically reduces aldehydes and ketones to alcohols but not carboxylic acids.
- H₂ with a catalyst like Pt (catalytic hydrogenation), which is not typically effective for reducing carboxylic acids to alcohols under standard conditions.
- Na and C₂H₅OH, which is used in the Bouveault-Blanc reduction to reduce esters to alcohols, not carboxylic acids directly.

3. Evaluating the Options:
- (A) LiAlH₄/ether: LiAlH₄ is a strong reducing agent that can reduce carboxylic acids to primary alcohols. The reaction proceeds as follows:
CH₃COOH + LiAlH₄ → CH₃CH₂OH (after hydrolysis). Ether is used as a solvent to facilitate the reaction.
- (B) H₂, Pt: Catalytic hydrogenation with H₂ and Pt is not effective for reducing carboxylic acids to alcohols under standard conditions; it’s more suited for reducing alkenes or alkynes.
- (C) NaBH₄: Sodium borohydride is a milder reducing agent and does not reduce carboxylic acids to alcohols; it typically reduces aldehydes and ketones.
- (D) Na and C₂H₅OH: This combination is used in the Bouveault-Blanc reduction, which reduces esters to alcohols, not carboxylic acids directly.

Final Answer:
The reagent that can perform the conversion is LiAlH₄/ether, so the answer is (A).

Answer 2

The given reaction is the reduction of acetic acid (CH₃COOH) to ethanol (CH₃CH₂OH).

Let's analyze each option:

• Option A: LiAlH₄ / ether: Lithium aluminum hydride (LiAlH₄) is a strong reducing agent that can reduce carboxylic acids to alcohols. The reaction with ether as the solvent is typical for this reduction, making this the correct choice.
• Option B: H₂, Pt: Hydrogen with platinum can reduce carboxylic acids to alcohols, but LiAlH₄ is more commonly used for this reduction.
• Option C: NaBH₄: Sodium borohydride (NaBH₄) is a milder reducing agent and can reduce aldehydes and ketones to alcohols, but it is not effective in reducing carboxylic acids.
• Option D: Na and C₂H₅OH: This combination does not serve as an effective reducing agent for carboxylic acids.

The correct answer is (A) : LiAlH₄ / ether.