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 problem of determining the final product of the reaction between propene (CH₃CH=CH₂) and NBS followed by AgCN, we will go through the reaction step by step.

### Step 1: Identify the Reactants
The initial reactant is propene, which can be represented as:
\[ \text{CH}_3\text{CH}=\text{CH}_2 \]

### Step 2: Reaction with NBS
NBS (N-Bromosuccinimide) is used for bromination at the allylic position via a free radical mechanism. In propene, the allylic position is the carbon adjacent to the double bond.

- The allylic carbon in propene is the carbon that is connected to the double bond. In this case, it is the carbon that is part of the CH₃ group.
- The reaction will result in the removal of one hydrogen from the allylic position and the addition of a bromine atom.

The product after bromination (let's call it compound A) will be:
\[ \text{CH}_2\text{BrCH}=\text{CH}_2 \]
This can be rearranged to:
\[ \text{CH}_2\text{Br-CH}=\text{CH}_2 \]

### Step 3: Reaction with AgCN
Next, we take compound A and react it with AgCN (Silver cyanide). This reaction involves a nucleophilic substitution mechanism.

- AgCN does not dissociate into ions, so the nucleophilic attack will be carried out by the nitrogen atom in the cyanide group (CN).
- The nitrogen will attack the carbon that is bonded to bromine in the compound A.

The product after this reaction (let's call it compound B) will be:
\[ \text{CH}_2\text{CN-CH}=\text{CH}_2 \]

### Final Product
Thus, the final product B after the reaction with AgCN is:
\[ \text{CH}_2\text{=CH-CH}_2\text{CN} \]

### Summary of the Final Product
The major product of the reaction sequence is:
\[ \text{CH}_2\text{=CH-CH}_2\text{CN} \]