In para-chlorophenol, the hydroxyl group and the chlorine atom are located on opposite sides of the benzene ring. This allows the hydroxyl groups of adjacent molecules to form hydrogen bonds more effectively, resulting in stronger intermolecular interactions and a higher melting point.
On the other hand, in ortho-chlorophenol, the hydroxyl group and the chlorine atom are adjacent to each other. This steric hindrance hinders the formation of intermolecular hydrogen bonds, weakening the intermolecular interactions. As a result, ortho-chlorophenol has a lower melting point compared to para-chlorophenol.
