Question

Account for the following:

Haloarenes are insoluble in water but are soluble in benzene.

Answer 1

1. Insolubility in Water: Water is a highly polar solvent with strong hydrogen bonding between its molecules. Haloarenes (aromatic rings with halogen substituents) are largely non-polar or only slightly polar due to the aromatic ring and the nature of the C–X bond (where X is a halogen). They cannot form significant hydrogen bonds with water molecules. Since “like dissolves like,” non-polar haloarenes do not dissolve well in polar water because they cannot effectively interact with the water molecules to break apart and disperse.
2. Solubility in Benzene: Benzene is a non-polar solvent and has strong van der Waals (dispersion) interactions with other non-polar molecules and slightly polar molecules like haloarenes. Haloarenes can interact well with benzene through these van der Waals forces because both consist predominantly of non-polar aromatic rings and similar electronic environments. This similarity in polarity leads to good solubility of haloarenes in benzene.

Hence, the solubility behavior of haloarenes can be explained by the principle of “like dissolves like.” Since haloarenes are mostly non-polar, they are insoluble in polar water but soluble in non-polar benzene.