Question

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

Why p-dichlorobenzene has higher melting point than those of ortho and meta-isomers?

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

Why is the melting point of p-dichlorobenzene higher than that of o- and m-isomers?

Answer 1

The melting point of p-dichlorobenzene is higher than that of its ortho- and meta-isomers due to its highly symmetrical structure. This symmetry allows the molecules to pack more efficiently and tightly in the crystal lattice, forming a more stable and orderly solid. As a result, stronger intermolecular forces hold the molecules together, and more energy (heat) is required to break these interactions during melting. In contrast, the less symmetrical o- and m-isomers pack less efficiently, have weaker intermolecular forces, and thus melt at lower temperatures.