Benzonitrile can be prepared from benzaldehyde on treatment with

Options

A. `NH_3`
B. `NH_3` followed by hydrogenation with NI
C. `NH_2 OH `
D. hydrogen cyanide.

Explanation

To prepare benzonitrile from benzaldehyde, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Reactants**: We start with benzaldehyde (C6H5CHO) as our starting material. We need to convert the aldehyde group (-CHO) into a nitrile group (-CN).

2. **Choose the Reagent**: To convert benzaldehyde to benzonitrile, we can use a reagent that introduces the cyanide group. A common reagent for this transformation is sodium cyanide (NaCN) or potassium cyanide (KCN) in the presence of a suitable acid.

3. **Reaction Mechanism**: The reaction involves a nucleophilic addition of the cyanide ion (CN-) to the carbonyl carbon of benzaldehyde. The mechanism can be outlined as follows:
- The cyanide ion attacks the electrophilic carbon of the carbonyl group in benzaldehyde.
- This results in the formation of a cyanohydrin intermediate.
- The cyanohydrin can then undergo dehydration (loss of water) to yield benzonitrile.

4. **Final Product**: The final product of this reaction is benzonitrile (C6H5CN).

### Summary of the Reaction:
Benzaldehyde + NaCN/KCN → Benzonitrile + H2O