Elimination of bromine from 2-bromobutane results in the formation of
(i)equimolar mixture of 1 and 2-butane
(ii)predominantly2-butene
(iii)predominantly 1-butene
(iv)predominantly 2-butyne.

Options

A. equimolar mixture of 1 and 2 butene
B. predominantly 1-butene
C. predominantly 1-butene
D. predominantly 2-butyne

Explanation

To solve the question regarding the elimination of bromine from 2-bromobutane, we can follow these steps:

### Step 1: Identify the Structure of 2-Bromobutane
2-bromobutane is a four-carbon alkane with a bromine atom attached to the second carbon. The structure can be represented as follows:

```
CH3-CH(Br)-CH2-CH3
```

### Step 2: Understand the Elimination Reaction
In an elimination reaction, a small group (in this case, bromine) is removed from a larger molecule, leading to the formation of a double bond. The reaction typically involves the removal of a hydrogen atom from a beta carbon and the halogen from the alpha carbon.

### Step 3: Identify Alpha and Beta Carbons
In 2-bromobutane:
- The alpha carbon is the one attached to the bromine (C2).
- The beta carbons are the carbons adjacent to the alpha carbon (C1 and C3).

### Step 4: Use a Strong Base for Elimination
When treated with a strong base like alcoholic KOH, the base will abstract a hydrogen atom from one of the beta carbons, leading to the formation of an alkene.

### Step 5: Determine Possible Products
1. **If H is removed from C1 (beta carbon)**:
- The product formed will be 1-butene:
```
CH2=CH-CH2-CH3 (1-butene)
```

2. **If H is removed from C3 (beta carbon)**:
- The product formed will be 2-butene:
```
CH3-CH=CH-CH3 (2-butene)
```

### Step 6: Apply Zaitsev's Rule
According to Zaitsev's rule, the more substituted alkene is favored in elimination reactions. In this case:
- 1-butene has one substituent (the double bond is at the end).
- 2-butene has more substituents (the double bond is in the middle and is more stable).

### Step 7: Conclusion
Since 2-butene is more substituted and therefore more stable than 1-butene, the predominant product of the elimination of bromine from 2-bromobutane will be predominantly 2-butene.

### Final Answer
The correct option is (ii) predominantly 2-butene.

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