(a) Show the formation of the electrophile in the following reactions : (i) CI_(2)+AICI_(3), (ii) HNO_(3)+H_(2)SO_(4), (iii) Br_(2)+Fe, (iv) H_(2)SO_(4), (v) H_(2)S_(2)O_(7), Fuming sulphuric acid. (b) How do substituent groups on an aromatic rign influence the course of electrophilic aromatic substituion ? Classify them by their effects.

(a) Show the formation of the electrophile in the following reactions

1.	(a) Show the formation of the electrophile in the following reactions : (i) CI_(2)+AICI_(3), (ii) HNO_(3)+H_(2)SO_(4), (iii) Br_(2)+Fe, (iv) H_(2)SO_(4), (v) H_(2)S_(2)O_(7), Fuming sulphuric acid. (b) How do substituent groups on an aromatic rign influence the course of electrophilic aromatic substituion ? Classify them by their effects.
Answer» Solution :(a) (i) `CI_(2)+AICI_(3)toCI^(+)+AICI_(4)^(-)` (ii) `HONO_(2)+HOSO_(3)HtoH_(2)O+NO_(2)^(+)+HSO_(4)^(-)` (iii) `2Fe+3FeBr_(2)to2FeBr_(3)` `FeBr_(3)+Br_(2)toBr^(+)+FeBr_(4)^(-)` (iv) `2H_(2)SO_(4)toH_(3)O^(+)+HSO_(4)^(-)+SO_(3)` (v)`H_(2)S_(2)O_(7)toH^(+)+HSO_(4)^(+)+SO_(3)` (B) The substituents on an aromatic ring affect the electrophilic substitution in two ways : 1. Reactivity : The compound is more reactive than benzene, the groups present are activating. In case, the compound is less reactive than benzene, the groups present are deactivating. 2. Orientation : Whether electrophile (E) enters ortho, para or meta. There are three CLASSES of SUBSTITUENT groups: (i)All activaing groups direct E to ortho or parapositions. (ii) Most deactivating groups direct E to meta-positions. ltbegt (iii) A few deactivating groups, e.g., halogens direct E to ortho or para-positions.