Electrophilic Aromatic Substitution. 10. A Kinetic Study of the Friedel-Crafts tert-Butylation Reaction in Nitromethane

Article abstract of DOI:10.1021/jo00359a039

A kinetic study of the reaction between tert-butyl chloride and benzene or toluene using aluminum chloride as catalyst was made in solvent nitromethane over the temperature range -27 to 10 deg C.The rate law was found to be first order in aromatic hydrocarbon, in tert-butyl chloride and in initial catalyst concentration.At -15 deg C k₃ for benzene = 6.7 (+/-1.0) * 10^-2M^-2s^-1; for toluene k₃ = 20 (+/-2)*10^-1M^-2s^-1 with product isomer percentages meta 4.6 +/- 0.3 and para 95.4 +/- 0.3.E_a is 76 +/- 13 kJ/mol, ΔH^<*> = 74 +/- 13 kJ/mol, and ΔS^<*> = 16 +/- 46 J/deg mol.Competitive results were k_T/k_B = 25 +/- 1, 4.9 +/- 0.1percent meta, 95.1 +/- 0.1percent para.The results fit Brown's selectivity relationship.A mechanism involving a rate-determining attack by a tert-butyl cation-AlCl4^- ion pair on the aromatic is proposed.