Which of the following will not be soluble in sodium bicarbonate?

Options

A. 2,4,6-Trinitrophenol
B. Benzoic aciid
C. o-Nitrophenol
D. Benzenesulphinic acid.

Explanation

To determine which of the following compounds will not be soluble in sodium bicarbonate, we need to analyze the acidity of each compound in relation to carbonic acid (H2CO3), which is the weak acid that sodium bicarbonate can react with.

### Step-by-Step Solution:

1. **Identify the Compounds**: The compounds in question are:
- Benzoic acid
- Ortho-nitrophenol
- Benzene sulfonic acid

2. **Understand Sodium Bicarbonate**: Sodium bicarbonate (NaHCO3) is a weak base and can react with acids to form carbonic acid (H2CO3) and a salt. The reaction is favorable when the acid is stronger than carbonic acid.

3. **Compare Acidity**:
- **Benzoic Acid**: This is a carboxylic acid and is more acidic than carbonic acid. Therefore, it will react with sodium bicarbonate and be soluble.
- **Ortho-nitrophenol**: This compound has intramolecular hydrogen bonding, which decreases its acidity. It is less acidic than carbonic acid, meaning it will not react with sodium bicarbonate and thus will not be soluble.
- **Benzene Sulfonic Acid**: This is a sulfonic acid and is stronger than carbonic acid. It will react with sodium bicarbonate and be soluble.

4. **Conclusion**: The compound that will not be soluble in sodium bicarbonate is **ortho-nitrophenol**.

### Final Answer:
**Ortho-nitrophenol will not be soluble in sodium bicarbonate.**