Which of the following is most acidic?

Options

A. Phenol
B. Benzyl alchol
C. `m-`Chlorophenol
D. Cyclohexanol

Explanation

To determine which of the given compounds is the most acidic, we will analyze the acidity of each compound step by step.

### Step 1: Identify the Compounds
The three compounds we need to compare are:
1. Phenol (C6H5OH)
2. Benzyl alcohol (C6H5CH2OH)
3. M-chloro-phenol (C6H4ClOH)

### Step 2: Understand the Nature of Acidity
Acidity in organic compounds is influenced by the stability of the conjugate base formed after deprotonation (loss of H+). The more stable the conjugate base, the stronger the acid.

### Step 3: Analyze Phenol
Phenol is an aromatic alcohol. When phenol loses a proton (H+), it forms the phenoxide ion (C6H5O−). The negative charge on the oxygen can be delocalized into the aromatic ring, stabilizing the conjugate base.

### Step 4: Analyze Benzyl Alcohol
Benzyl alcohol is an aliphatic alcohol. When it loses a proton, it forms the benzyl anion (C6H5CH2−). The negative charge is localized on the carbon atom and is not stabilized by resonance with an aromatic system, making it less stable than the phenoxide ion.

### Step 5: Analyze M-chloro-phenol
M-chloro-phenol has a chlorine atom attached to the meta position of the phenolic ring. The chlorine atom is an electron-withdrawing group (due to its electronegativity) and exerts a -I (inductive) effect. This effect decreases the electron density on the oxygen atom of the phenolic group, which increases the acidity of m-chloro-phenol compared to phenol.

### Step 6: Compare the Acidity
- **Phenol**: Moderate acidity due to resonance stabilization of the phenoxide ion.
- **Benzyl Alcohol**: Least acidic due to lack of resonance stabilization in the conjugate base.
- **M-chloro-phenol**: More acidic than phenol because the -I effect from the chlorine atom stabilizes the conjugate base by reducing electron density.

### Conclusion
Among the three compounds, **M-chloro-phenol** is the most acidic due to the presence of the electron-withdrawing chlorine atom, which stabilizes the conjugate base more effectively than in phenol or benzyl alcohol.

### Final Answer
The most acidic compound is **M-chloro-phenol**.

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