The increasing order of acidity among phenol , p-methylphenol , m-nitrophenol and p-nitrophenol is

Options

A. m-nitrophenol , p-nitrophenol, phenol , p-methylphenol
B. p-methylphenol , m-nitrophenol, phenol , p-nitrophenol
C. p-methylphenol, phenol , m-nitrophenol, p-nitrophenol
D. phenol , p-methylphenol, p-nitrophenol , m-nitrophenol

Explanation

To determine the increasing order of acidity among phenol, p-methylphenol, m-nitrophenol, and p-nitrophenol, we will analyze the stability of their conjugate bases after the deprotonation of the hydroxyl group (-OH). The more stable the conjugate base, the stronger the acid.

### Step-by-Step Solution:

1. **Identify the Structures**:
- **Phenol (C6H5OH)**: A benzene ring with a hydroxyl group.
- **p-Methylphenol (C6H4(CH3)OH)**: A benzene ring with a methyl group at the para position relative to the hydroxyl group.
- **m-Nitrophenol (C6H4(NO2)OH)**: A benzene ring with a nitro group at the meta position relative to the hydroxyl group.
- **p-Nitrophenol (C6H4(NO2)OH)**: A benzene ring with a nitro group at the para position relative to the hydroxyl group.

2. **Draw Conjugate Bases**:
- When phenols lose a proton (H+), they form phenoxide ions. The stability of these ions will help us determine the acidity.
- **Phenoxide Ion from Phenol**: The negative charge is localized on the oxygen.
- **Phenoxide Ion from p-Methylphenol**: The methyl group is an electron-donating group (+I effect), which destabilizes the negative charge.
- **Phenoxide Ion from m-Nitrophenol**: The nitro group at the meta position does not stabilize the negative charge effectively.
- **Phenoxide Ion from p-Nitrophenol**: The nitro group at the para position stabilizes the negative charge through resonance and the -M effect.

3. **Analyze Stability of Conjugate Bases**:
- **p-Nitrophenol**: The conjugate base is stabilized by resonance due to the -M effect of the nitro group, making it the strongest acid.
- **m-Nitrophenol**: The conjugate base is less stable than p-nitrophenol because the nitro group does not stabilize the negative charge effectively.
- **Phenol**: The conjugate base is less stable than m-nitrophenol due to the absence of any electron-withdrawing groups.
- **p-Methylphenol**: The conjugate base is the least stable due to the destabilizing +I effect of the methyl group.

4. **Order of Acidity**:
- Based on the stability of the conjugate bases, we can arrange the compounds in increasing order of acidity:
- p-Methylphenol < Phenol < m-Nitrophenol < p-Nitrophenol

### Final Answer:
The increasing order of acidity is:
**p-Methylphenol < Phenol < m-Nitrophenol < p-Nitrophenol**