Compounds A, B and C in the following reaction sequence are:
` C_(2) H_(5)Br overset("AgCN")(rarr) A overset(H3O^(+))(rarr)` B + C

Options

A. `C_(2) H_(5)CN, C_(2)H_(5)"COOH", NH_(3)`
B. `C_(2)H_(5)"NC", C_(2) H_(5) NH_(2),"HCOOH"`
C. `C_(2)H_(5)"NC", C_(2) H_(5) "NHCH"_(3),"HCOOH"`
D. none of these

Answer

To solve the problem, we need to identify the compounds A, B, and C in the given reaction sequence involving the compound C2H5Br (ethyl bromide) reacting with AgCN and subsequently undergoing hydrolysis with H3O+.

### Step-by-Step Solution:

1. **Identify the Initial Compound**:
The starting compound is C2H5Br, which can be written as CH3CH2Br (ethyl bromide).

2. **Reaction with AgCN**:
When C2H5Br reacts with AgCN, a nucleophilic substitution occurs. In this case, the nucleophile is not CN⁻ directly because AgCN does not dissociate to release CN⁻ ions due to the strong covalent bond between Ag and CN. Instead, the nitrogen atom of the isocyanide (AgCN) acts as the nucleophile.

- **Reaction**:
\[ CH3CH2Br + AgCN \rightarrow CH3CH2NC + AgBr \]
- **Compound A**: The product formed is ethyl isocyanide (CH3CH2NC).

3. **Hydrolysis of Compound A**:
The next step involves the hydrolysis of compound A (ethyl isocyanide) using H3O⁺. During hydrolysis, the isocyanide will react with water and H⁺ ions.

- **Mechanism**:
- The nitrogen in the isocyanide has a lone pair that can attack a proton (H⁺) from H3O⁺, leading to a positively charged intermediate.
- Water (H2O) can then attack the carbon atom, leading to the formation of an unstable intermediate.

- **Intermediate Formation**:
\[ CH3CH2NC + H3O^+ \rightarrow CH3CH2N^+(H)C \text{(unstable)} \]

4. **Formation of Compounds B and C**:
The unstable intermediate will rearrange and undergo further reactions, leading to the formation of two products, B and C.

- **Final Products**:
- **Compound B**: The stable product formed after hydrolysis is ethylamine (C2H5NH2).
- **Compound C**: The other product formed is formic acid (HCOOH).

5. **Final Identification**:
- **Compound A**: Ethyl isocyanide (CH3CH2NC)
- **Compound B**: Ethylamine (C2H5NH2)
- **Compound C**: Formic acid (HCOOH)

### Summary of Compounds:
- **A**: CH3CH2NC (ethyl isocyanide)
- **B**: C2H5NH2 (ethylamine)
- **C**: HCOOH (formic acid)