Benzene has a lower boiling point (80.1 °C) than toluene (110.6 °C) due to its stronger intermolecular forces. Benzene molecules are held together by stronger London dispersion forces compared to toluene. London dispersion forces are temporary attractions that arise due to the constant motion of electrons within the molecule.

The symmetrical electron distribution in benzene allows for efficient stacking of molecules, maximizing these London dispersion forces. In contrast, toluene has a methyl group attached to the benzene ring, introducing asymmetry and disrupting the efficient stacking. The presence of the methyl group also introduces additional steric hindrance, which further inhibits close packing of toluene molecules. As a result, the intermolecular forces in benzene are stronger, leading to a lower boiling point.

Higher Melting Point of Benzene:

Benzene has a much higher melting point (5.5 °C) compared to toluene (-95 °C) due to its higher lattice energy. In the solid state, benzene molecules are arranged in a highly ordered crystalline lattice. The stronger London dispersion forces in benzene contribute to a more stable and rigid lattice structure.

On the other hand, the presence of the methyl group in toluene disrupts the efficient stacking of molecules in the solid state. The methyl group hinders the close packing and introduces asymmetry into the lattice structure, resulting in weaker intermolecular forces. This weaker lattice structure in toluene leads to a lower melting point.

In summary, benzene's lower boiling point can be attributed to its stronger intermolecular forces in the liquid state, while its higher melting point is a consequence of its stronger lattice energy in the solid state.