Give reasons-
(ii) The dipole moment of chlorobenzene is lower than that of cyclohexyl chloride.

Explanation

In chlorobenzene, C-atom of the C-Cl bond is `sp^(2)` -hybridised, thus it is more electronegative than the corresponding `sp^(3)` -hybridised carbon of chloro-cyclohexana. Consequently, attraction of bonding electron pair away from carbon by chlorine is less pronounced in chlorobenzene than in cyclohexyl chloride and so, molecular dipole moment is smaller in chlorobenzene.

Futher, chlorobenzene is a resonance hybrid of the given resonation structures and so, there exsists a `pi`-moment. Thus `pi`- moment acts in opposition to that of the strong `sigma`-moment arising out of the highly polar `C rarr Cl` bond. The resultant dipole moment of chlorobenzene is thus smaller than that of cyclohexyl chloride (it has no resonance structure and so, no `pi`-moment).
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