In dénydrohalogenation of tert-pentyl bromide using alc. KOH, major product obtained is

Options

A. 2-Methylbut-1-ene
B. 2-Methylbut-2-ene
C. Pen! 1-ene
D. Pent-2 ene

Answer

To determine the major product obtained from the dehydrohalogenation of tert-pentyl bromide using alcoholic KOH, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Structure of tert-Pentyl Bromide**:
- tert-Pentyl bromide has the structure of a tertiary alkyl halide. The molecular formula is C5H11Br.
- The structure can be represented as:
```
CH3
|
CH3-C-CH2-CH3
|
Br
```

2. **Understand the Reaction Conditions**:
- The reaction is conducted using alcoholic KOH, which acts as a strong base.
- This will favor an elimination reaction (E2 mechanism) rather than substitution.

3. **Identify the Mechanism**:
- In the E2 mechanism, a hydrogen atom is removed from a β-carbon (the carbon adjacent to the carbon bearing the leaving group, Br in this case) along with the leaving group (Br).
- The elimination leads to the formation of a double bond.

4. **Locate the β-Hydrogens**:
- In the structure of tert-pentyl bromide, the β-carbons are the ones adjacent to the carbon attached to the bromine.
- The β-carbons are the ones that have hydrogen atoms that can be eliminated.

5. **Determine the Possible Products**:
- If we remove a β-hydrogen from the β-carbon that is attached to two other carbons (the one in the middle), we will form the more substituted alkene.
- The possible elimination can occur from either of the β-carbons, but we will focus on the one that leads to the more stable (more substituted) alkene.

6. **Formation of the Major Product**:
- By removing a β-hydrogen from the carbon adjacent to the tertiary carbon (the one with Br), we will form 2-methylbutene.
- The structure of the major product (2-methylbutene) can be represented as:
```
CH3
|
CH2=C-CH2-CH3
|
CH3
```

7. **Conclusion**:
- The major product obtained from the dehydrohalogenation of tert-pentyl bromide using alcoholic KOH is 2-methylbutene.

### Final Answer:
The major product is **2-methylbutene**.