Strongest acid amon the following is

Options

A. o-methoxyphenol
B. p-methoxyphenol
C. m-methoxyphenol
D. phenol

Explanation

To determine the strongest acid among the given compounds: ortho-methoxyphenol, para-methoxyphenol, meta-methoxyphenol, and phenol, we will analyze the effects of the methoxy group (-OCH3) on the acidity of phenol.

### Step-by-Step Solution:

1. **Identify the Compounds**:
- The compounds to compare are:
- Ortho-methoxyphenol
- Para-methoxyphenol
- Meta-methoxyphenol
- Phenol

2. **Understand the Role of the Methoxy Group**:
- The methoxy group (-OCH3) is an electron-donating group through resonance (it has a +M effect) and can also exhibit a -I (inductive) effect.
- The resonance effect will increase electron density on the aromatic ring, while the inductive effect will withdraw electron density.

3. **Analyze Each Compound**:
- **Ortho-methoxyphenol**: The methoxy group is in the ortho position, which increases electron density via resonance (+M effect), but the -I effect destabilizes the negative charge on the conjugate base (phenoxide ion) formed upon deprotonation.
- **Para-methoxyphenol**: Similar to ortho, the para position also allows for resonance (+M effect) but has less steric hindrance compared to ortho. The -I effect still destabilizes the conjugate base.
- **Meta-methoxyphenol**: The methoxy group in the meta position does not participate in resonance with the hydroxyl group (-OH). Thus, there is no destabilizing +M effect, and the -I effect is less impactful here.
- **Phenol**: In phenol, there is no methoxy group, so it has a baseline acidity.

4. **Compare the Acidity**:
- The acidity of a compound is determined by the stability of its conjugate base. The more stable the conjugate base, the stronger the acid.
- In meta-methoxyphenol, the absence of destabilizing resonance means that the conjugate base is more stable compared to ortho and para-methoxyphenol.
- Therefore, meta-methoxyphenol has the highest acidity among the four.

5. **Conclusion**:
- The strongest acid among the given options is **meta-methoxyphenol**.

### Final Answer:
**Meta-methoxyphenol is the strongest acid among the given options.**

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