p-Dichlorobenzene has higher melting point and lower solubility than those of o- and m-isomers. Explain.

Answer : p-Dichlorobenzene has higher melting point and lower solubility than those of corresponding o- and m-isomers. This is due to the reason that p-isomers being more symmetrical fit closely in the crystal lattice; hence, intermolecular forces in p-isomers are stronger than in those o- and m-isomers. As a result, more energy is required to melt or dissolve p-isomers than the corresponding o- and m-isomers.