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

Answer

To determine the increasing order of acidity among phenol, p-methylphenol, m-nitrophenol, and p-nitrophenol, we need to analyze the stability of their conjugate bases. The more stable the conjugate base, the stronger the acid.

### Step-by-Step Solution:

1. **Identify the Compounds:**
- Phenol (C6H5OH)
- p-Methylphenol (C6H4(CH3)OH)
- m-Nitrophenol (C6H4(NO2)OH)
- p-Nitrophenol (C6H4(NO2)OH)

2. **Understand Acidity and Conjugate Bases:**
- Acidity is determined by the stability of the conjugate base formed after the acid donates a proton (H+).
- For phenols, the conjugate base is formed by deprotonating the hydroxyl group (OH), resulting in a phenoxide ion (C6H5O−).

3. **Analyze Each Compound:**
- **Phenol:** The phenoxide ion formed is stabilized by resonance. The negative charge on the oxygen can delocalize into the aromatic ring, making it relatively stable.
- **p-Methylphenol:** The methyl group (CH3) is an electron-donating group (due to +I effect), which destabilizes the phenoxide ion by increasing electron density on the negatively charged oxygen. Thus, it is less acidic than phenol.
- **m-Nitrophenol:** The nitro group (NO2) is an electron-withdrawing group, but because it is in the meta position, it does not effectively stabilize the negative charge on the oxygen through resonance. Therefore, it has moderate acidity.
- **p-Nitrophenol:** The nitro group is in the para position, which allows it to stabilize the negative charge on the phenoxide ion through resonance. This makes p-nitrophenol more acidic than both phenol and m-nitrophenol.

4. **Rank the Acidity:**
- p-Nitrophenol > m-Nitrophenol > Phenol > p-Methylphenol
- Thus, the increasing order of acidity is:
- p-Methylphenol < Phenol < m-Nitrophenol < p-Nitrophenol

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