Which of the following is not an example of +E effect:

Options

A. (A) Hydrohalognation of Propene
B. (B) Hydroboration of propyne
C. (C) Formation of acetaldehydecyanohydrine
D. (D) Hydration of ethene

Answer

To solve the question "Which of the following is not an example of +E effect?", we will follow these steps:

### Step 1: Understand the +E Effect
The +E effect, or positive electromeric effect, occurs when there is a complete transfer of pi electrons in the presence of an electrophile. This effect is temporary and requires the substrate to have a double or triple bond.

### Step 2: Analyze the Given Options
We need to evaluate each option to determine if it is an example of the +E effect. The options typically involve reactions of compounds with double or triple bonds.

### Step 3: Evaluate Each Option
1. **Hydrohalogenation of Propene**:
- Propene has a double bond (C=C).
- The electrophile (HX) attacks the double bond, leading to the +E effect.
- Conclusion: This is an example of +E effect.

2. **Hydroboration of Propyne**:
- Propyne has a triple bond (C≡C).
- The electrophile attacks the triple bond, resulting in the +E effect.
- Conclusion: This is also an example of +E effect.

3. **Formation of Acetyldehyde Cyanohydrin**:
- In this reaction, the electrophile attacks the carbonyl carbon (C=O) rather than a double or triple bond.
- Since there is no double or triple bond involved in the attack, this does not exhibit the +E effect.
- Conclusion: This is NOT an example of +E effect.

4. **Hydration of Ethene**:
- Ethene has a double bond (C=C).
- The electrophile (H+) attacks the double bond, leading to the +E effect.
- Conclusion: This is an example of +E effect.

### Step 4: Identify the Correct Answer
From the analysis, the only option that does not demonstrate the +E effect is the **formation of acetyldehyde cyanohydrin**.

### Final Answer
**Option 3: Formation of Acetyldehyde Cyanohydrin is not an example of +E effect.**

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