Question

Explain why the dipole moment of chalarobenzene is lower than that of cyclohexyl chloride

Answer 1

Due to sp2 hybridisation of C-atom in chlorobenzene, C-atom is more electronegative (greater s-character) whereas in cyclohexyl chloride,C-atom is sp hybridised, i.e. less electronegative (lesser s-character). So, polarity of C—Cl bond in chlorobenzene is less than the C—Cl bond in cyclohexyl chloride. Further, due to delocalisation of lone pair of electrons of Cl-atom over the benzene ring, C—Cl bond in chlorobenzene acquires some double bond character while C—Cl bond in cyclohexyl chloride is a pure single bond. Thus, C—Cl bond in chlorobenzene is shorter than in cyclohexyl chloride. As dipole moment is a product of charge and distance, therefore, the dipole moment of chlorobenzene is lower than that of cyclohexyl chloride.