Which of the following isomers is move volatile : o-nitrophenol or p-nitrophenol

Explanation

To determine which isomer is more volatile between o-nitrophenol (ortho-nitrophenol) and p-nitrophenol (para-nitrophenol), we can analyze their structures and the type of hydrogen bonding present in each compound.

### Step-by-Step Solution:

1. **Identify the Structures of the Isomers**:
- **Ortho-nitrophenol (o-nitrophenol)**: The nitro group (-NO2) is positioned adjacent to the hydroxyl group (-OH) on the benzene ring.
- **Para-nitrophenol (p-nitrophenol)**: The nitro group is positioned opposite the hydroxyl group on the benzene ring.

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