Increasing order of acidic strength among `p-`methoxyphenol `(i)p-`methylphenol `(II)` and `p-`nitrophenol `(III)` is

Options

A. p - nitorphenopl , p - methoxyphenol , p - methylphenol
B. p - methylphenol , p - methoxyphenol , p - nitrophenol
C. p - nitorphenol , p - methyphenol , p - methoxyphenol
D. p - methoxyphenol , p - methylphenol , p - nitrophenol

Answer

To determine the increasing order of acidic strength among p-methoxyphenol (I), p-methylphenol (II), and p-nitrophenol (III), we need to analyze the effects of the substituents on the phenolic compound's acidity.

### Step-by-Step Solution:

1. **Identify the Compounds**:
- p-Methoxyphenol (I): Contains a methoxy group (-OCH₃) at the para position relative to the hydroxyl (-OH) group.
- p-Methylphenol (II): Contains a methyl group (-CH₃) at the para position relative to the hydroxyl (-OH) group.
- p-Nitrophenol (III): Contains a nitro group (-NO₂) at the para position relative to the hydroxyl (-OH) group.

2. **Understand the Nature of Substituents**:
- The methoxy group (-OCH₃) is an electron-donating group due to its +M (mesomeric) effect. This increases the electron density on the benzene ring and destabilizes the phenoxide ion formed when phenol loses a proton, thus decreasing acidity.
- The methyl group (-CH₃) is also an electron-donating group, primarily through its +I (inductive) effect, which similarly decreases acidity but is less effective than the methoxy group.
- The nitro group (-NO₂) is an electron-withdrawing group due to its -M (mesomeric) and -I (inductive) effects. This decreases the electron density on the benzene ring and stabilizes the phenoxide ion, thus increasing acidity.

3. **Compare the Acidity**:
- p-Methoxyphenol (I) has the weakest acidity due to the strong electron-donating effect of the methoxy group.
- p-Methylphenol (II) is slightly more acidic than p-methoxyphenol because the methyl group is a weaker electron-donating group compared to the methoxy group.
- p-Nitrophenol (III) is the most acidic due to the strong electron-withdrawing effect of the nitro group, which stabilizes the phenoxide ion.

4. **Establish the Increasing Order of Acidity**:
- Based on the analysis, the order of acidity from weakest to strongest is:
- p-Methoxyphenol (I) < p-Methylphenol (II) < p-Nitrophenol (III)

### Final Answer:
The increasing order of acidic strength is:
**p-Methoxyphenol (I) < p-Methylphenol (II) < p-Nitrophenol (III)**