Select correct regarding acidic strength of given compounds: (1) o-methylbenzoic acid (2) m-methylbenzoic acid (3). P-methylbenzoic acid (4) benzoic acid.

Options

A. 1gt2gt3gt4
B. 4gt3gt2gt1
C. 1gt4gt2gt3
D. 3gt2gt4gt1

Answer

To determine the correct order of acidic strength for the given compounds (1) o-methylbenzoic acid, (2) m-methylbenzoic acid, (3) p-methylbenzoic acid, and (4) benzoic acid, we will analyze the effects of the methyl group on the acidity of benzoic acid.

### Step-by-Step Solution:

1. **Identify the Compounds**:
- (1) o-methylbenzoic acid (ortho position)
- (2) m-methylbenzoic acid (meta position)
- (3) p-methylbenzoic acid (para position)
- (4) benzoic acid (no substituent)

2. **Understand the Ortho Effect**:
- Ortho-substituted benzoic acids (like o-methylbenzoic acid) exhibit increased acidity due to the ortho effect. The proximity of the methyl group can stabilize the carboxylate ion formed after deprotonation.

3. **Evaluate the Effects of the Methyl Group**:
- The methyl group is an electron-donating group due to hyperconjugation and +I (inductive) effect. This effect generally decreases acidity because it destabilizes the negative charge on the carboxylate ion.

4. **Rank the Acidity**:
- **Most Acidic**: o-methylbenzoic acid (due to the ortho effect).
- **Next**: benzoic acid (no substituents, hence no destabilization).
- **Next**: m-methylbenzoic acid (the methyl group has less destabilizing effect compared to para).
- **Least Acidic**: p-methylbenzoic acid (the methyl group has both +I and hyperconjugation effects, which are more pronounced at the para position).

5. **Final Order of Acidity**:
- The order of acidic strength is:
1. o-methylbenzoic acid (most acidic)
2. benzoic acid
3. m-methylbenzoic acid
4. p-methylbenzoic acid (least acidic)

### Final Answer:
The correct order of acidic strength is:
**o-methylbenzoic acid > benzoic acid > m-methylbenzoic acid > p-methylbenzoic acid.**