p-Dichlorobenzene has higher m.p. than those of o- and m-isomers. Discuss

Explanation

The p-isomer being more symmetrical fits closely in the crystal lattice and thus has stronger inter-
molecular forces of attraction than o- and m-isomers. Since during melting or dissolution, the crystal lattice breaks, therefore, a large amount of energy is needed to melt or dissolve the p-isomer than the corresponding o-and m-isomers. ln other words, the melting point of the p-isomer is higher and its solubility lower than the corresponding o-and m-isomers.