Understanding the Reaction of Benzoic Acid with Lithium Aluminium Hydride

The question asks about the product formed when Benzoic acid reacts with lithium aluminium hydride.

Let's first understand the reactants:

• Benzoic acid: This is a carboxylic acid with the chemical formula $\text{C}_6\text{H}_5\text{COOH}$. It contains a phenyl group attached to a carboxyl group.
• Lithium aluminium hydride ($\text{LiAlH}_4$): This is a very strong reducing agent commonly used in organic chemistry. It is capable of reducing various functional groups, including carboxylic acids, esters, amides, nitriles, and epoxides.

Reduction of Carboxylic Acids by $\text{LiAlH}_4$

Lithium aluminium hydride is known to reduce carboxylic acids to primary alcohols. The reaction typically involves the hydride ion ($\text{H}^-$) attacking the electrophilic carbonyl carbon, followed by elimination steps and further reduction. The overall process effectively replaces the carbon-oxygen double bond and the $\text{-OH}$ group of the carboxyl group with $\text{-CH}_2\text{-}$.

The general reaction for the reduction of a carboxylic acid ($\text{RCOOH}$) with $\text{LiAlH}_4$ is:

\(\text{RCOOH} \xrightarrow{\text{1. LiAlH}_4, \text{ ether}} \text{RCH}_2\text{OH}\)
\(\phantom{\text{RCOOH}} \xrightarrow{\text{2. H}_2\text{O}}\)

In this reaction, the carboxylic acid is reduced to the corresponding primary alcohol.

Applying the Reaction to Benzoic Acid

When Benzoic acid reacts with lithium aluminium hydride, the carboxyl group ($\text{-COOH}$) attached to the phenyl ring is reduced to a primary alcohol group ($\text{-CH}_2\text{OH}$).

The structure of Benzoic acid is:

\(\text{C}_6\text{H}_5\text{-COOH}\)

The product formed after reduction with $\text{LiAlH}_4$ will be the compound where the $\text{-COOH}$ group is converted to $\text{-CH}_2\text{OH}$. This compound is benzyl alcohol.

The structure of benzyl alcohol is:

\(\text{C}_6\text{H}_5\text{-CH}_2\text{OH}\)

The reaction can be written as:

\(\text{C}_6\text{H}_5\text{COOH} \xrightarrow{\text{1. LiAlH}_4, \text{ ether}} \text{C}_6\text{H}_5\text{CH}_2\text{OH}\)
\(\phantom{\text{C}_6\text{H}_5\text{COOH}} \xrightarrow{\text{2. H}_2\text{O}}\)

Thus, the reaction of Benzoic acid with lithium aluminium hydride yields benzyl alcohol.

Analyzing the Options

Let's look at the given options:

1. Benzene ($\text{C}_6\text{H}_6$): This is an aromatic hydrocarbon. It is not the product of this reduction reaction.
2. Benzyl alcohol ($\text{C}_6\text{H}_5\text{CH}_2\text{OH}$): This is a primary alcohol and matches the product we determined from the reduction of Benzoic acid.
3. Toluene ($\text{C}_6\text{H}_5\text{CH}_3$): This is methylbenzene. It is not the product of this reduction reaction.
4. None of the above: This would be correct only if none of the above options were the product.

Based on the chemistry of $\text{LiAlH}_4$ reduction of carboxylic acids, the product of the reaction of Benzoic acid is indeed benzyl alcohol.

In summary, Benzoic acid reacts with lithium aluminium hydride to produce benzyl alcohol through a reduction process.