Which of the following is most acidic ?

Options

A. Benzyl alcohol
B. Cyclohexanol
C. Phenol
D. m-chlorophenol

Explanation

To determine which of the given compounds is the most acidic, we need to analyze the structures and the effects of substituents on acidity.

### Step-by-Step Solution:

1. **Identify the Compounds**:
- The compounds given are:
1. Benzyl alcohol (C6H5CH2OH)
2. Cyclohexanol (C6H11OH)
3. Phenol (C6H5OH)
4. Meta-chlorophenol (C6H4ClOH)

2. **Understand Acidity**:
- Acidity is influenced by the ability of a compound to donate a proton (H+). The presence of electron-withdrawing groups (EWGs) increases acidity, while electron-donating groups (EDGs) decrease acidity.

3. **Analyze Each Compound**:
- **Benzyl Alcohol**: The hydroxyl (OH) group is attached to a carbon that is sp3 hybridized. This makes it less acidic because sp3 hybridized carbons do not stabilize the negative charge on the conjugate base effectively.
- **Cyclohexanol**: Similar to benzyl alcohol, the OH group is attached to a sp3 hybridized carbon, making it also less acidic.
- **Phenol**: The OH group is attached to a sp2 hybridized carbon in the benzene ring. The resonance stabilization of the phenoxide ion (the conjugate base) increases the acidity compared to benzyl alcohol and cyclohexanol.
- **Meta-Chlorophenol**: The chlorine atom is an electron-withdrawing group due to its electronegativity and ability to stabilize the negative charge through inductive effects. This increases the acidity of meta-chlorophenol compared to phenol.

4. **Compare Acidity**:
- Between benzyl alcohol and cyclohexanol, both are less acidic.
- Phenol is more acidic than both benzyl alcohol and cyclohexanol due to resonance stabilization.
- Meta-chlorophenol is the most acidic because the chlorine atom withdraws electron density, stabilizing the conjugate base even further.

5. **Conclusion**:
- The most acidic compound among the given options is **Meta-Chlorophenol**.

### Final Answer:
**Meta-Chlorophenol is the most acidic compound.**

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