The melting point of 2-nitrophenol is lower than that of 4-nitrophenol and this is because of:

• A. intramolecular hydrogen bonding in 2-nitrophenol
• B. intramolecular hydrogen bonding in 4-nitrophenol
• C. intermolecular hydrogen bonding in 2-nitrophenol
• D. hydrogen bonding has no relation to the melting point

The melting point difference between 2-nitrophenol and 4-nitrophenol can be attributed to the presence of intramolecular hydrogen bonding in 2-nitrophenol. This bonding occurs within the same molecule, which stabilizes its structure and lowers its melting point compared to 4-nitrophenol, where such bonding is not as significant.

Key Points to Remember

• Intramolecular hydrogen bonding: This occurs when a hydrogen bond forms between atoms within the same molecule, affecting its stability.
• Melting point: The temperature at which a solid becomes a liquid; influenced by molecular interactions.
• 2-nitrophenol vs. 4-nitrophenol: The position of the nitro group affects the type of hydrogen bonding that can occur.

Therefore, the correct answer is A. intramolecular hydrogen bonding in 2-nitrophenol.