Which of the following is steam volatile

Options

A. Phenol
B. o-Nitrophenol
C. m - Nitrophenol
D. p - Nitrophenol

Explanation

To determine which of the given compounds is steam volatile, we need to analyze the structures and intermolecular interactions of each compound. The compounds in question are phenol, ortho-nitrophenol, meta-nitrophenol, and para-nitrophenol.

### Step-by-Step Solution:

1. **Identify the Structures**:
- **Phenol**: A benzene ring with a hydroxyl (OH) group attached.
- **Ortho-nitrophenol**: A phenol with a nitro (NO2) group attached to the adjacent carbon (ortho position) of the benzene ring.
- **Meta-nitrophenol**: A phenol with a nitro group attached to the carbon that is one position away from the hydroxyl group (meta position).
- **Para-nitrophenol**: A phenol with a nitro group attached to the carbon directly opposite the hydroxyl group (para position).

2. **Analyze Intermolecular Forces**:
- **Phenol**: Exhibits hydrogen bonding between molecules due to the presence of the hydroxyl group.
- **Ortho-nitrophenol**: Exhibits intramolecular hydrogen bonding between the hydroxyl group and the nitro group, which reduces intermolecular hydrogen bonding.
- **Meta-nitrophenol**: Exhibits intermolecular hydrogen bonding similar to phenol but with a slightly higher boiling point due to the position of the nitro group.
- **Para-nitrophenol**: Also exhibits intermolecular hydrogen bonding, but the distance between the hydroxyl and nitro groups is greater than in ortho-nitrophenol, leading to stronger intermolecular forces compared to ortho-nitrophenol.

3. **Determine Volatility**:
- The compound with the lowest boiling point will be the most steam volatile.
- **Ortho-nitrophenol** has intramolecular hydrogen bonding, which decreases its intermolecular interactions, leading to a lower boiling point compared to the other compounds.
- **Phenol**, **meta-nitrophenol**, and **para-nitrophenol** have stronger intermolecular hydrogen bonding, resulting in higher boiling points.

4. **Conclusion**:
- Based on the analysis, **ortho-nitrophenol** is the most steam volatile compound due to its intramolecular hydrogen bonding, which reduces the boiling point.

### Final Answer:
**Ortho-nitrophenol** is steam volatile.