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ExamsJEE AdvancedChemistry

o-Nitrophenol has a lower solubility in water than its m- and p-isomers mainly because:

  1. The melting point of o-nitrophenol is lower than that of the m- and p-isomers.
  2. o-Nitrophenol is more volatile in steam than the m- and p-isomers.
  3. o-Nitrophenol exhibits intramolecular hydrogen bonding.
  4. o-Nitrophenol exhibits intermolecular hydrogen bonding.

Correct answer: o-Nitrophenol exhibits intramolecular hydrogen bonding.

Solution

In o-nitrophenol the -OH and adjacent -NO2 form an intramolecular (chelate) hydrogen bond, so the molecule cannot hydrogen-bond effectively with water, lowering its water solubility. In the m- and p-isomers the groups are too far apart, so they hydrogen-bond with water and dissolve better.

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