Rearrange the following in the increasing order of acidic strength.
(i) benzoic acid (ii) p-methoxybenzoic acid (iii) o -methyoxybenzoic acid

Options

A. `ilt ii lt iii`
B. `iii lt ilt ii`
C. `ii lt ilt iii`
D. `iii lt ii lt i`

Explanation

To determine the increasing order of acidic strength among benzoic acid, p-methoxybenzoic acid, and o-methoxybenzoic acid, we need to analyze how the methoxy group (–OCH3) affects the acidity of benzoic acid.

### Step-by-Step Solution:

1. **Identify the Compounds**:
- **Benzoic Acid (C6H5COOH)**: This is the simplest carboxylic acid with a carboxyl group (-COOH) directly attached to a benzene ring.
- **p-Methoxybenzoic Acid (C6H4(OCH3)COOH)**: This compound has a methoxy group (-OCH3) attached to the para position relative to the carboxylic acid group.
- **o-Methoxybenzoic Acid (C6H4(OCH3)COOH)**: This compound has a methoxy group attached to the ortho position relative to the carboxylic acid group.

2. **Understand the Effect of Methoxy Group**:
- The methoxy group is an electron-donating group due to its +M (mesomeric) effect. This means it can donate electron density to the benzene ring.
- Electron-donating groups generally decrease the acidity of carboxylic acids because they destabilize the negative charge on the conjugate base (the carboxylate ion) formed after deprotonation.

3. **Analyze the Position of the Methoxy Group**:
- In **p-methoxybenzoic acid**, the methoxy group is at the para position. The electron-donating effect is present, but it does not have any significant steric hindrance or additional resonance stabilization.
- In **o-methoxybenzoic acid**, the methoxy group is at the ortho position. Here, the ortho effect comes into play. The proximity of the methoxy group can lead to steric hindrance and resonance effects that stabilize the conjugate base more than in the para case.

4. **Rank the Acidity**:
- **o-Methoxybenzoic Acid**: The ortho effect increases the acidity due to steric hindrance and resonance stabilization of the conjugate base. Therefore, it is the most acidic.
- **Benzoic Acid**: This is the baseline compound with no electron-donating groups affecting its acidity.
- **p-Methoxybenzoic Acid**: The methoxy group at the para position decreases acidity the most, making it the least acidic among the three.

5. **Final Order**:
- Increasing order of acidic strength:
- p-methoxybenzoic acid < benzoic acid < o-methoxybenzoic acid.

### Conclusion:
The increasing order of acidic strength is:
**p-methoxybenzoic acid < benzoic acid < o-methoxybenzoic acid.**