The correct order of acid strength of the following substituted phenols in water at `28^(@)C` is

Options

A. p-nitrophenolltp-fluorophenolltp-chlorophenol
B. p-chlorophenolltp-fluorophenolltp-nitrophenol
C. p-flurophenolltp-chlorophenolltp-nitro-phenol
D. p-flurophenolltp-nitrophenolltp-chlorophenol

Explanation

To determine the correct order of acid strength of substituted phenols in water at 28°C, we need to analyze the effects of the substituents on the phenolic compound's ability to donate a proton (H⁺).

### Step-by-Step Solution:

1. **Identify the Substituted Phenols**:
Let's consider the substituted phenols mentioned: para-nitrophenol (p-NO₂C₆H₄OH) and para-chlorophenol (p-ClC₆H₄OH).

2. **Understand the Concept of Acidity**:
The acidity of phenols is influenced by the stability of the phenoxide ion (the conjugate base formed after deprotonation). The more stable the phenoxide ion, the stronger the acid.

3. **Analyze the Effects of Substituents**:
- **Para-Nitrophenol**: The nitro group (NO₂) is a strong electron-withdrawing group through both resonance and inductive effects. This increases the stability of the phenoxide ion by delocalizing the negative charge.
- **Para-Chlorophenol**: The chloro group (Cl) is also an electron-withdrawing group, but it is less effective than the nitro group. Chlorine withdraws electrons mainly through an inductive effect and has a weak resonance effect.

4. **Compare the Stability of Conjugate Bases**:
- The phenoxide ion from para-nitrophenol is more stable due to the strong electron-withdrawing nature of the nitro group, which stabilizes the negative charge.
- The phenoxide ion from para-chlorophenol is less stable compared to that of para-nitrophenol because the chlorine is a weaker electron-withdrawing group.

5. **Establish the Order of Acidity**:
Based on the stability of the conjugate bases, we can conclude that:
- Para-nitrophenol is a stronger acid than para-chlorophenol.

Thus, the correct order of acid strength of the substituted phenols in water at 28°C is:
**p-Nitrophenol > p-Chlorophenol**

### Final Answer:
**The correct order of acid strength is: para-nitrophenol > para-chlorophenol.**

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