How will you explain the directive influence of (i)-CH=CH_2 and(ii) -C Cl_3 group when attached to the benzene ring ?

How will you explain the directive influence of (i)-CH=CH_2 and(ii) -C

1.	How will you explain the directive influence of (i)-CH=CH_2 and(ii) -C Cl_3 group when attached to the benzene ring ?
Answer» Solution :(i)Stability of the carbocation INTERMEDIATE can be used to explain the o,p-directing influence of the `-CH=CH_2` as follows : Only carbocations resulting from o- and p-substitution are STABILIZED by spreading the charge on the side chain while each such type of stabilization is not possible in case of m-substitution. Thus, `-CH=CH_2` GROUP is o,p-directing . Similarly, we can explain the directive influence of `C_6H_5` group which is also o,p-directing. (ii)Hyperconjugation effect can be used to explain the directive influence of `C Cl_3` group as DISCUSSED below . Due to the presence of +ve charge at o- and p-positions , the ELECTRON density is comparatively more at m-positions. Therefore , `-C Cl_3` is a m-directing group.