Give reasons:
(i). `C-Cl` bond length in chlorobenzene is shorter than `C-Cl` bond length in `CH_(3)-Cl`
(ii). The dipole moment of chlorobenzene is less than of cyclohexyl chloride.
(c). `S_(N^(1))` reactions are accompanied by racemisation is optically active alkyl halides.

Explanation

(i) C - Cl bond length in chlorobenzene is shorter than C- Cl bond length in `CH_(3) - Cl` because of resonance in chlorobenzene, C- Cl bond in chlorobenzene has double bond character, which makes it shorter in length.

(ii) The carbon in chlorobenzene is `SP^(2)` hybridised having greater S-character, making it more electronegative. Hence, `SP^(2)` hybrid carbon of C - Cl bond in chlorobenzene is less polar than cyclohexyl chloride having `SP^(3)` hybridised carbon. Therefore, dipole moment of chlorobenzene is lower than that of cyclohexyl chloride.

(iii) `S_(N)1` reactions are accompained by recemization in optically active alkyle nalides. This is due to the reason that carbocation being `SP^(2)` hybridised are planar species therefore, the attack of nucleophile on it can occur from both the faces with almost equal ease giving a 50 : 50 mixture of two enantiomers.