(A) Finish the resonance forms of the sigma complex for the electrophilic aromatic substitution of bromobenzene where the electrophile lands para to the bromine. You should get a total of four resonance forms; the fourth one is something you haven't seen but explains why halogens are ortho/para directors for the second EAS. FⓇ :Br: H R.D.S. :Br: Three more (B) Could you get this fourth resonance form if the electrophile (E) landed meta to the bromine? (C) Even though the halogens are ortho/para directors the EAS runs slower than the EAS of benzene. Sketch the reaction coordinate diagram that shows the relative energies (i.e. stabilities) of the sigma complexes for para EAS, meta EAS and for the EAS of benzene (i.e. reference). As an option, speculate why the EAS on a phenyl halide runs slower than benzene even though halogens are ortho / para directors
An electrophile substitutes an atom that is attached to an aromatic ring in electrophilic aromatic substitution reactions, that are organic processes. Typically, in such reactions, an electrophile takes the place of a hydrogen atom from a benzene ring.
In these electrophilic aromatic substitution (EAS) reactions, there are different groups that directs the incoming electrophile in different position w.r.t. the substituents. Like electron releasing substituents like bromo(-Br), chloro(-Cl), methoxy(-OCH3), methyl(-CH3) etc. on the benzene ring directs the incoming electrophile to the ortho/para position w.r.t. the substituents.
Whereas, electron withdrawing group like nitro(-NO2), ester(-COOR), etc. direct the incoming electrophile to meta position w.r.t. the substituents.
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