What is the final product of the following reaction?
`CH_(3) CH = CH_(2) + NBS rarr " A " overset("AgCN")(rarr)`B (Major)

Options

A. `CH_(3)`CH =CHCN
B. `CH_(3) `CH = CHNC
C. `CH_(2) = CHCH_(2)`CN
D. `CH_(2) = CHCH_(2)`NC

Answer

To solve the question regarding the final product of the reaction involving `CH3CH=CH2` with N-bromosuccinimide (NBS) followed by treatment with silver cyanide (AgCN), we can break it down into steps:

### Step-by-Step Solution:

1. **Identify the Reactants**:
The starting compound is `CH3CH=CH2`, which is propene. The reagents involved are N-bromosuccinimide (NBS) and silver cyanide (AgCN).

**Hint**: Recognize the structure of the alkene and the reagents involved.

2. **Reaction with NBS**:
NBS is used for allylic bromination. In this reaction, the hydrogen atom on the carbon adjacent to the double bond (the allylic position) will be replaced by a bromine atom.

- The allylic carbon in propene is the one next to the double bond, which is `CH2` in `CH3-CH=CH2`.
- The product of this reaction (let's call it Product A) will be `CH3-CHBr-CH2`.

**Hint**: Remember that NBS selectively brominates the allylic position.

3. **Formation of Product A**:
The product A can be represented as:
\[ \text{A} = CH3-CHBr-CH2 \]

**Hint**: Write down the structure of Product A to visualize the bromination.

4. **Reaction with AgCN**:
Next, we treat Product A with silver cyanide (AgCN). AgCN dissociates into Ag+ and CN-. The bromine atom in Product A is a good leaving group due to its electronegativity.

- The CN- ion acts as a nucleophile and attacks the carbon atom bonded to bromine, leading to the substitution of bromine with the cyanide group.

5. **Formation of Product B**:
The final product (let's call it Product B) will be:
\[ \text{B} = CH3-CH(CN)-CH2 \]
This structure can also be written as:
\[ \text{B} = CH2=CH-CH2-CN \]
However, the major product will be the one where the cyanide is attached to the allylic carbon.

**Hint**: Identify the major product by considering the stability of the resulting structure.

### Final Answer:
The final product of the reaction is:
\[ \text{B} = CH3-CH(CN)-CH2 \]