The following compound is obtained by the reduction of benzoic acid with lithium alumimium hydride –

Options

A. Cyclohexanoic acid
B. Benzylalcohol
C. Cyclohexa–1, 4–dioic acid
D. No reaction

Answer

To solve the question regarding the compound obtained by the reduction of benzoic acid with lithium aluminium hydride (LiAlH4), we will follow these steps:

### Step 1: Identify the Reactants
The reactant in this case is benzoic acid, which has the molecular formula C6H5COOH. It contains a carboxylic acid functional group (-COOH).

**Hint:** Remember that benzoic acid is an aromatic carboxylic acid with a phenyl group attached to a carboxyl group.

### Step 2: Understand the Reducing Agent
Lithium aluminium hydride (LiAlH4) is a strong reducing agent commonly used to reduce carboxylic acids to primary alcohols.

**Hint:** LiAlH4 donates hydride ions (H-) which can reduce carbonyl groups.

### Step 3: Mechanism of Reduction
1. The hydride ion from LiAlH4 attacks the carbonyl carbon of the carboxylic acid, resulting in the formation of a tetrahedral intermediate. The carbonyl oxygen becomes negatively charged (alkoxide ion).

2. The tetrahedral intermediate can be represented as:
- C6H5C(OH)(O-)H

**Hint:** The attack of the hydride ion leads to the formation of a negatively charged oxygen.

### Step 4: Protonation of the Alkoxide
In the presence of water (which is often used to quench the reaction), the negatively charged oxygen will pick up a proton (H+) from water, leading to the formation of a primary alcohol.

3. The product formed after protonation is benzyl alcohol (C6H5CH2OH).

**Hint:** The final product is a primary alcohol, which is characterized by the -OH group attached to a carbon that is bonded to only one other carbon atom.

### Step 5: Conclusion
The compound obtained from the reduction of benzoic acid with lithium aluminium hydride is benzyl alcohol.

**Final Answer:** Benzyl alcohol (C6H5CH2OH).

### Summary of Options
- Option 1: Cyclohexanoic acid - Incorrect
- Option 2: Benzyl alcohol - Correct
- Option 3: Cyclohexane-1,4-dioic acid - Incorrect
- Option 4: No reaction - Incorrect

**Correct Answer:** Option 2 - Benzyl alcohol.