One among the following compounds will not give effervescence with sodium carbonate:

Options

A. `C_6H_5CO_2H`
B.
C. `C_6H_5OH`
D.

Explanation

To determine which compound will not give effervescence with sodium carbonate (Na2CO3), we need to understand the conditions under which effervescence occurs. Effervescence is typically observed when carbon dioxide (CO2) is released, which happens when sodium carbonate reacts with an acid. Strong acids will react with sodium carbonate to produce carbon dioxide, while weak acids will not.

### Step-by-Step Solution:

1. **Identify the Reaction**: Sodium carbonate reacts with acids to produce carbon dioxide gas, which leads to effervescence. The general reaction is:
\[ \text{Acid} + \text{Na}_2\text{CO}_3 \rightarrow \text{Salt} + \text{H}_2\text{O} + \text{CO}_2 \uparrow \]

2. **Analyze the Given Compounds**: We need to analyze the acidic strength of the compounds provided in the options. The stronger the acid, the more likely it is to react with sodium carbonate and produce effervescence.

3. **Evaluate Each Compound**:
- **C6H5COOH (Benzoic Acid)**: This is a carboxylic acid and is considered a relatively strong acid due to resonance stabilization of its conjugate base (benzoate ion). It will react with sodium carbonate and produce CO2.
- **C6H5SO3H (Benzene Sulfonic Acid)**: This is also a strong acid. The sulfonate ion formed after deprotonation is highly stabilized due to resonance with multiple oxygen atoms, making it a strong acid that will also react with Na2CO3.
- **C6H5OH (Phenol)**: Phenol is a weak acid compared to the previous two. The phenoxide ion formed after deprotonation is less stable due to the lack of equivalent resonance structures, which makes phenol a weaker acid. It is less likely to react with sodium carbonate to produce CO2.
- **3-Nitrophenol**: This compound has a nitro group, which is a strong electron-withdrawing group. This increases the acidic strength of 3-nitrophenol compared to phenol, making it more likely to react with sodium carbonate.

4. **Conclusion**: Among the given compounds, phenol (C6H5OH) is the least acidic and will not produce effervescence when reacted with sodium carbonate. Therefore, the correct answer is:
\[ \text{C6H5OH (Phenol)} \]

### Final Answer:
**Option C: C6H5OH (Phenol)** will not give effervescence with sodium carbonate.