Which is most acidic

Options

A.
B.
C.
D.

Answer

To determine which compound is the most acidic among the given options (cyclohexanol, benzyl alcohol, and phenol), we need to analyze the stability of the conjugate bases formed after the release of a proton (H⁺). The acidity of a compound is directly related to the stability of its conjugate base; the more stable the conjugate base, the more acidic the compound.

### Step-by-Step Solution:

1. **Identify the Compounds**: The compounds we are comparing are:
- Cyclohexanol
- Benzyl alcohol
- Phenol

2. **Understand Acidity**: Acidity is determined by the ease of releasing a proton (H⁺). The stability of the conjugate base formed after deprotonation is crucial.

3. **Analyze Each Compound**:
- **Cyclohexanol**: When cyclohexanol loses a proton, it forms cyclohexoxide (C₆H₁₁O⁻). There is no resonance stabilization in this conjugate base, making it less stable.
- **Benzyl Alcohol**: When benzyl alcohol loses a proton, it forms benzyl oxide (C₆H₅CH₂O⁻). This conjugate base can exhibit some resonance stabilization because the negative charge can be delocalized onto the benzene ring.
- **Phenol**: When phenol loses a proton, it forms phenoxide (C₆H₅O⁻). The negative charge on the oxygen can be delocalized into the aromatic ring through resonance, which significantly stabilizes the conjugate base.

4. **Compare Stability of Conjugate Bases**:
- Cyclohexoxide has no resonance stabilization.
- Benzyl oxide has some resonance stabilization.
- Phenoxide has strong resonance stabilization, making it the most stable among the three.

5. **Conclusion**: Since phenoxide is the most stable conjugate base due to resonance, phenol is the most acidic compound among the options given.

### Final Answer: **Phenol (Option D) is the most acidic.**

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