o-Nitrophenol is less soluble in water than p-nitrophenol because :
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → o-Nitrophenol shows intramolecular H-bonding
Solubility in water depends on how well a molecule can form hydrogen bonds with water.
In o-nitrophenol the –OH and –\( \ce{NO2} \) groups are next to each other, so the O–H forms a hydrogen bond with an oxygen of the nitro group inside the same molecule (intramolecular, a six-membered chelate ring). The –OH is “used up” and is hardly available to hydrogen-bond with water, so o-nitrophenol is less soluble.
In p-nitrophenol the groups are far apart; its –OH and –\( \ce{NO2} \) groups are free to form intermolecular hydrogen bonds with water, so it is more soluble.
Why the other options are incorrect
Option (1) o-Nitrophenol is more steam volatile than p-nitrophenol — Incorrect. True, but it is another result of the same intramolecular H-bond, not the reason for the lower solubility.
Option (3) o-Nitrophenol shows intermolecular H-bonding — Incorrect. False; intermolecular H-bonding is shown by p-nitrophenol.
Option (4) Melting point of o-nitrophenol is lower than p-nitrophenol — Incorrect. Also true, but a lower melting point does not explain lower solubility; both follow from the intramolecular H-bond.
NCERT (2026-27 edition):
Electrophilic Aromatic Substitution – “… o-Nitrophenol is steam volatile due to intramolecular hydrogen bonding while p-nitrophenol is less volatile due to intermolecular hydrogen bonding which causes the association of molecules.”