Which of the following nucleophiles has highest tendency for `S_(N)2` reactions?

Options

A. MeOH
B. `MeCH_(2)OH`
C. `Me_(2)CHOH`
D. `Me_(3)COH`

Answer

To determine which nucleophile has the highest tendency for \( S_N2 \) reactions, we need to consider the following factors:

1. **Nature of the Nucleophile**: Nucleophiles are species that have a lone pair of electrons and can donate them to an electrophile. The strength of a nucleophile is influenced by its basicity and steric hindrance.

2. **Steric Hindrance**: In \( S_N2 \) reactions, the nucleophile attacks the electrophile from the opposite side of the leaving group. If the nucleophile is bulky (large in size), it will have difficulty approaching the electrophile due to steric hindrance. Therefore, smaller nucleophiles are generally better for \( S_N2 \) reactions.

3. **Comparison of Given Nucleophiles**:
- **Option 1: \( CH_3OH \)** (Methanol)
- **Option 2: \( CH_3CH_2OH \)** (Ethanol)
- **Option 3: \( CH_3CH_2CH_2OH \)** (Propanol)
- **Option 4: \( CH_3(CH_2)_2OH \)** (Butanol)

4. **Analyzing Each Option**:
- **Option 1**: Methanol has the smallest size and the least steric hindrance, making it a good nucleophile for \( S_N2 \) reactions.
- **Option 2**: Ethanol is larger than methanol, which introduces more steric hindrance, making it less effective as a nucleophile in \( S_N2 \) reactions.
- **Option 3**: Propanol is even larger, leading to increased steric hindrance compared to ethanol.
- **Option 4**: Butanol is the largest of the four, resulting in the highest steric hindrance and the least nucleophilicity.

5. **Conclusion**: Based on the analysis, methanol (\( CH_3OH \)) is the nucleophile with the highest tendency for \( S_N2 \) reactions due to its smaller size and lower steric hindrance.

**Final Answer**: The nucleophile with the highest tendency for \( S_N2 \) reactions is **Option 1: \( CH_3OH \)**.

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