1. In each of the cases below, determine which benzene is more reactive, in electrophilic aromatic substitution reactions? Provide a thorough explanation for each case. a. CH3 b. C. d. CH3 NEt₂ or or or or OCH3 CH₂CH3 Br NO₂
Electrophilic aromatic substitution reaction: The addition of electrophile(E+) to benzene results in substitution instead of addition as in alkenes and alkynes. This reaction is facilitated by generally by Lewis acid.
The rate of the reaction is effected by the presence of different substituents.
The electron donating groups or ring activating groups increases the rate of reaction because the more electron density moves on to the ring while electrophilic substitution.
Examples : RO-(alkoxide), -OR(alkoxy), -OH(hydroxy), -NH2(amine), -NHC(O)-(amide). -C(O)-O-(ester) and alkyl(R) groups.
The electron withdrawing groups or ring deactivating groups decreases the rate of reaction because the electron density moves from the ring towards the electron withdrawing group which reduces the electron density on the ring.
Examples : -CN(cyano), -NO2(nitro), -CCl3(haloalkyl), -C(O)-R(carbonyl, -SO3R(sulfonyl) -N+H3R(ammonium) and halo groups.
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