The dehydrohalogenation of neopentyl bromide with alcoholic KOH mainly gives

Options

A. 2-methyl-1-butene
B. 2-methyl-2-butene
C. 2,2-dimethyl-1-butene
D. 2-butene

Explanation

To solve the question regarding the dehydrohalogenation of neopentyl bromide with alcoholic KOH, we can follow these steps:

### Step 1: Understand the Structure of Neopentyl Bromide
Neopentyl bromide is a branched alkyl halide with the formula C5H11Br. Its structure can be represented as follows:

```
CH3
|
CH3-C-CH2-Br
|
CH3
```

### Step 2: Identify the Reaction Type
Dehydrohalogenation is a reaction where a hydrogen halide (in this case, HBr) is eliminated from an alkyl halide. The reaction typically occurs in the presence of a strong base, such as alcoholic KOH.

### Step 3: Mechanism of Dehydrohalogenation
In the presence of alcoholic KOH, the base abstracts a proton (H) from a carbon adjacent to the carbon bonded to the bromine atom (the β-carbon). This leads to the formation of a double bond (alkene) as the bromine leaves.

### Step 4: Determine the Possible Products
For neopentyl bromide, the β-hydrogens are located on the carbon atoms adjacent to the carbon bonded to bromine. The elimination can occur in two ways:
1. Removal of H from the primary carbon (leading to the formation of 2-methyl-1-butene).
2. Removal of H from the tertiary carbon (leading to the formation of 2-methyl-2-butene).

### Step 5: Analyze the Stability of the Products
The stability of alkenes is influenced by the degree of substitution:
- 2-methyl-1-butene is a less substituted alkene (only one substituent on the double bond).
- 2-methyl-2-butene is a more substituted alkene (two substituents on the double bond).

More substituted alkenes are generally more stable due to hyperconjugation and the inductive effect.

### Step 6: Conclusion
Since 2-methyl-2-butene is more stable than 2-methyl-1-butene, the major product of the dehydrohalogenation of neopentyl bromide with alcoholic KOH will be **2-methyl-2-butene**.

### Final Answer
The main product of the dehydrohalogenation of neopentyl bromide with alcoholic KOH is **2-methyl-2-butene**.

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