`C_6 H_5 N_2 Cl underset( " Pyridine ") overset ( Cu_2 (CN ) _2 ) to A overset( H_3 O^(+) ) to B ` . Here [B] is

Options

A. Cyanobenzene
B. Benezamide
C. Benzene
D. Benzoic acid

Answer

To solve the problem step by step, we will analyze the reactions involved with the given diazonium salt and the reagents used.

### Step 1: Identify the Reactants
The starting compound is C₆H₅N₂Cl, which is a diazonium salt. The reaction involves pyridine and Cu₂(CN)₂.

### Step 2: Reaction with Cu₂(CN)₂
When the diazonium salt (C₆H₅N₂Cl) reacts with Cu₂(CN)₂ in the presence of pyridine, it undergoes a reaction known as the Sandmeyer reaction. This reaction replaces the diazonium group (N₂) with a cyano group (C≡N).

The reaction can be represented as:
\[ C_6H_5N_2Cl + Cu_2(CN)_2 \xrightarrow{Pyridine} C_6H_5C \equiv N + HCl + N_2 \]

The product formed here is benzonitrile (C₆H₅C≡N).

### Step 3: Hydrolysis of Benzonitrile
Next, the benzonitrile (C₆H₅C≡N) is subjected to hydrolysis in the presence of hydronium ions (H₃O⁺). Hydrolysis of nitriles typically leads to the formation of amides.

The hydrolysis reaction can be represented as:
\[ C_6H_5C \equiv N + H_3O^+ \rightarrow C_6H_5C(=O)NH_2 \]

The product formed here is benzoamide (C₆H₅C(=O)NH₂).

### Conclusion
Thus, the final product [B] after the reactions is **benzoamide (C₆H₅C(=O)NH₂)**.

### Summary of the Steps
1. Identify the reactants: C₆H₅N₂Cl (diazonium salt).
2. React with Cu₂(CN)₂ in pyridine to form benzonitrile (C₆H₅C≡N).
3. Hydrolyze benzonitrile with H₃O⁺ to form benzoamide (C₆H₅C(=O)NH₂).