Which of the following reaction shall produce benzoic acid ?

Options

A.
B.
C.
D.

Answer

To determine which reactions produce benzoic acid, we will analyze the given reactions step by step.

### Step 1: Analyzing the first reaction with bromobenzene and magnesium (Mg)
1. **Starting Material**: Bromobenzene (C6H5Br)
2. **Reaction with Magnesium**: When bromobenzene reacts with magnesium in dry ether, it forms a Grignard reagent (C6H5MgBr).
3. **Reaction with Carbon Dioxide**: The Grignard reagent (C6H5MgBr) then reacts with carbon dioxide (CO2) to form a carboxylate intermediate (C6H5COOMgBr).
4. **Hydrolysis**: Upon hydrolysis (addition of water), the carboxylate intermediate converts to benzoic acid (C6H5COOH).

**Conclusion for Step 1**: This reaction produces benzoic acid.

### Step 2: Analyzing the second reaction with nitrobenzene and HCl
1. **Starting Material**: Nitrobenzene (C6H5NO2)
2. **Reduction with HCl**: The nitro group (NO2) is reduced to an amino group (NH2) using HCl and a reducing agent.
3. **Final Product**: The product of this reaction is aniline (C6H5NH2), not benzoic acid.

**Conclusion for Step 2**: This reaction does not produce benzoic acid.

### Step 3: Analyzing the third reaction with bromobenzene, sodium cyanide (NaCN), and HCl
1. **Starting Material**: Bromobenzene (C6H5Br)
2. **Nucleophilic Substitution**: When bromobenzene reacts with sodium cyanide (NaCN), the bromine atom is replaced by a cyano group (C≡N), forming benzonitrile (C6H5CN).
3. **Hydrolysis**: Upon hydrolysis (addition of water and acid), benzonitrile is converted to benzoic acid (C6H5COOH).

**Conclusion for Step 3**: This reaction produces benzoic acid.

### Step 4: Analyzing the fourth reaction
1. **Starting Material**: The details of the fourth reaction are not provided, but based on the previous analysis, we can conclude that if it does not involve a pathway to form a carboxylic acid from a suitable precursor, it will not yield benzoic acid.

**Conclusion for Step 4**: This reaction does not produce benzoic acid.

### Final Answer
The reactions that produce benzoic acid are:
1. The reaction of bromobenzene with magnesium followed by carbon dioxide and hydrolysis.
2. The reaction of bromobenzene with sodium cyanide followed by hydrolysis.