Ortho and Para nitrophenols can be separated by steam distillation. This is because
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → o-nitrophenol undergoes intramolecular hydrogen bonding
Reason:
Ortho-nitrophenol (o-nitrophenol) and para-nitrophenol (p-nitrophenol) can be separated by steam distillation because of the difference in their volatility, which arises due to hydrogen bonding:
- o-Nitrophenol: The –OH and –NO₂ groups are close → forms intramolecular hydrogen bonding → Molecules exist as discrete units (no association) → Lower boiling point, steam volatile
- p-Nitrophenol: Intramolecular H-bonding is not possible → forms intermolecular hydrogen bonding → Molecules associate strongly → higher boiling point, not steam volatile
During steam distillation, o-nitrophenol distills over with steam, while p-nitrophenol remains in the flask.
Why others are incorrect:
- ☀ p-nitrophenol undergoes intramolecular hydrogen bonding → False (it undergoes intermolecular)
- ☀ o-nitrophenol undergoes intermolecular hydrogen bonding → False (it undergoes intramolecular)
- ☀ o-nitrophenol is water soluble → False (both are sparingly soluble; separation is due to volatility, not solubility)