Which statement is false for elimination reaction .

Options

A. `beta`-elimination is more common than `alpha` & `gamma` elimination
B. In`beta`-elimination , formation of multiple bond occur
C. `beta`-elimination may be E1, E2 or E1cB
D. E1 & E2 requires presence of poor leaving group but E1cB requires presence of good leaving group.

Explanation

To determine which statement is false regarding elimination reactions, we will analyze the given statements step by step.

### Step 1: Understand the Types of Elimination Reactions
Elimination reactions can be classified mainly into two types: E1 and E2 mechanisms.

- **E1 Mechanism**: This is a two-step process where the leaving group departs first, forming a carbocation, followed by the elimination of a proton to form a double bond.
- **E2 Mechanism**: This is a one-step process where the base abstracts a proton while the leaving group departs simultaneously, forming a double bond.

### Step 2: Analyze the Statements
1. **Beta elimination is more common than alpha and gamma elimination.**
- **True**: Beta elimination is indeed more common because it involves the removal of a hydrogen atom from the beta position relative to the leaving group, which is generally more favorable.

2. **In beta elimination, formation of multiple bonds occurs.**
- **True**: In beta elimination, the removal of a proton and a leaving group leads to the formation of a double bond (alkene), which is a multiple bond.

3. **Beta elimination may be E1, E2, or E1cb.**
- **True**: Beta elimination can occur through E1, E2, or E1cb mechanisms, depending on the conditions and the structure of the substrate.

4. **E1 and E2 require the presence of a poor leaving group, but E1cb requires the presence of a good leaving group.**
- **False**: E1 and E2 mechanisms typically require a good leaving group for the reaction to proceed. E1cb, on the other hand, can occur with a poor leaving group under certain conditions, but it does not require a good leaving group.

### Step 3: Identify the False Statement
Based on the analysis, the false statement is:
**"E1 and E2 require the presence of a poor leaving group, but E1cb requires the presence of a good leaving group."**

### Final Answer
The correct answer is the statement regarding E1 and E2 requiring a poor leaving group, which is false.

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