Experiment 15:. SUBSTITUENT EFFECTS ON THE RATE OF ELECTROPHILIC AROMATIC SUBSTITUTION. Objectives:. To explore how different substituent groups on an aromatic ring affect the rate and orientation of electrophilic aromatic substitution using a qualitative bromine test.
SUBSTITUENT EFFECTS ON THE RATE OF ELECTROPHILIC AROMATIC SUBSTITUTION
An electron pair from the aromatic ring attacks Br2, forming a new C-Br bond…
…and leaving a nonaromatic, carbocation intermediate.
The carbocation intermediate loses H+, and the neutral substitution product forms as two electrons from the C-H bond move to regenerate the aromatic ring. HBr forms as a byproduct.
H < Phenyl < CH3 < NHCOCH3 < OCH3 < OH < NH2
NO2 < COR < CHO < I < Br < Cl < F < H