o-nitrophenol is more volatile than p-nitrophenol it is due to

Options

A. Intermolecular hydrogen bonding in o- nitrophenol
B. Intramolecular hydrogen bonding in o- nitrophenol
C. Intramolecular hydrogen bonding in p-nitrophenol
D. More resonating structure of p-nitrophenol

Answer

To determine why o-nitrophenol is more volatile than p-nitrophenol, we can analyze the molecular structures and the presence of hydrogen bonding in both compounds.

### Step-by-Step Solution:

1. **Understanding the Structures**:
- **Ortho-Nitrophenol (o-nitrophenol)** has the nitro group (-NO2) and the hydroxyl group (-OH) on adjacent carbon atoms of the benzene ring.
- **Para-Nitrophenol (p-nitrophenol)** has the nitro group and the hydroxyl group on opposite sides of the benzene ring.

2. **Hydrogen Bonding**:
- In o-nitrophenol, the proximity of the -OH group and the -NO2 group allows for the formation of intramolecular hydrogen bonds. This means that the hydrogen atom of the hydroxyl group can form a bond with the oxygen atom of the nitro group within the same molecule.
- In contrast, p-nitrophenol does not have this capability because the -OH and -NO2 groups are too far apart to form such a bond.

3. **Effect of Hydrogen Bonding on Volatility**:
- The presence of intramolecular hydrogen bonding in o-nitrophenol stabilizes the molecule, making it less likely to interact with other molecules in the liquid phase. This results in a lower boiling point and higher volatility.
- In p-nitrophenol, the absence of such hydrogen bonding leads to stronger intermolecular forces (like dipole-dipole interactions) between molecules, which increases its boiling point and decreases volatility.

4. **Conclusion**:
- Therefore, o-nitrophenol is more volatile than p-nitrophenol due to the presence of intramolecular hydrogen bonding in o-nitrophenol, which is not present in p-nitrophenol.

### Final Answer:
o-nitrophenol is more volatile than p-nitrophenol due to the presence of intramolecular hydrogen bonding in o-nitrophenol.

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