Which of the following will be the major product when 3 - phenylpropene reacts with HBr?

Options

A. `C_(6)H_(5)CH_(2)CHBrCH_(3)`
B. `C_(6)H_(5)CHBrCHCH_(2)`
C. `C_(6)H_(5)CH_(2)CH_(2)CH_(2)Br`
D. `C_(6)H_(5)CHBrCH_(2)CH_(3)`

Answer

To determine the major product when 3-phenylpropene reacts with HBr, we can follow these steps:

### Step 1: Identify the Structure of 3-Phenylpropene
3-Phenylpropene has a phenyl group (C6H5) attached to a propene chain. The structure can be represented as follows:

```
C6H5
|
H2C=C-CH2-CH3
```

### Step 2: Understand the Reaction with HBr
When 3-phenylpropene reacts with HBr, the alkene (C=C) will undergo electrophilic addition. The double bond will react with HBr, where H+ will add to one carbon and Br- will add to the other carbon.

### Step 3: Determine Possible Carbocation Formation
When HBr adds to the double bond, two possible carbocations can form:
1. If H+ adds to the terminal carbon (CH2), a primary carbocation is formed.
2. If H+ adds to the carbon adjacent to the phenyl group, a secondary carbocation is formed.

The secondary carbocation is more stable due to the resonance stabilization provided by the phenyl group.

### Step 4: Identify the More Stable Carbocation
The more stable carbocation will be formed when H+ adds to the carbon adjacent to the phenyl group. This results in a secondary carbocation:

```
C6H5
|
H2C-CH+-CH3
```

### Step 5: Carbocation Rearrangement
The secondary carbocation can undergo rearrangement. The positive charge can shift to the carbon adjacent to the phenyl group, which is stabilized by resonance from the phenyl ring.

### Step 6: Nucleophilic Attack by Br-
Once the more stable carbocation is formed, the Br- ion will attack the positively charged carbon, leading to the final product.

### Step 7: Write the Final Product
The final product of the reaction will be:

```
C6H5-CHBr-CH2-CH3
```

This can be represented as:
- C6H5CHBrCH2CH3

### Conclusion
The major product when 3-phenylpropene reacts with HBr is **C6H5CHBrCH2CH3**.