2-Bromopentane is treated with alcoholic KOH solution. The major product formed in this reaction and the type of reaction respectively are

Options

A. pent-2-ene, `beta`-elimination
B. pent-l-ene, `beta`-elimination
C. pentan-2-ol, nucleophilic substitution
D. pent-1-ene, nucleophilic substitution

Explanation

To solve the problem of what major product is formed when 2-Bromopentane is treated with alcoholic KOH, let's break down the reaction step by step.

### Step 1: Identify the Reactants
We start with 2-Bromopentane, which has the following structure:
- **Structure**: CH3-CH2-CHBr-CH2-CH3

### Step 2: Understand the Role of Alcoholic KOH
Alcoholic KOH is a strong base and will promote elimination reactions (dehydrohalogenation) rather than substitution reactions. The hydroxide ion (OH-) acts as a base to abstract a proton (H+) from the adjacent carbon atom.

### Step 3: Mechanism of the Reaction
1. The KOH will abstract a proton from the carbon adjacent to the carbon bearing the bromine atom (the β-carbon).
2. This results in the formation of a double bond (alkene) and the elimination of bromide ion (Br-).

### Step 4: Determine Possible Products
When 2-Bromopentane undergoes elimination:
- If the proton is removed from the carbon adjacent to the carbon with Br (C-3), the product will be:
- **Product 1**: CH3-CH=CH-CH2-CH3 (2-pentene)
- If the proton is removed from the other adjacent carbon (C-2), the product will be:
- **Product 2**: CH3-CH2-CH=CH-CH3 (1-pentene)

### Step 5: Stability of the Alkenes
To determine which alkene is the major product, we assess the stability of the alkenes formed:
- 2-pentene (Product 1) has more alkyl substituents around the double bond, making it more stable due to hyperconjugation and the inductive effect.
- 1-pentene (Product 2) is less stable as it has fewer substituents.

### Step 6: Conclusion
The major product formed is **2-pentene**, and the type of reaction is **β-elimination** (also known as dehydrohalogenation).

### Final Answer
The major product formed is **2-pentene**, and the type of reaction is **β-elimination**.

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