Inverse phase transfer catalysis. Kinetics of the pyridine 1-oxide-catalyzed reactions of dichlorobenzoyl chlorides and benzoate ions

Abstract

The substitution reactions of 2,3-, 2,4-, 3,4-, or 3,5-dichlorobenzoyl chloride (Cl 2C 6H 3COCl) and 2,3-, 2,4-, 3,4-, or 3,5-dichlorobenzoate ion (Cl 2C 6H 5COO −) or benzoate ion (C 6H 5COO −) in a two-phase H 2O/CH 2Cl 2 medium using pyridine 1-oxide (PNO) as an inverse phase transfer catalyst were investigated. The reaction of Cl 2C 6H 3COCl and PNO in CH 2Cl 2 to produce the ionic intermediate, 1-(dichlorobenzoyloxy)-pyridinium chloride (Cl 2C 6H 3COONP +Cl −) is the rate-determining step. In the PNO-catalyzed two-phase reaction of Cl 2C 6H 3COCl and C 6H 5COONa, the order of reactivities of Cl 2C 6H 3COCl toward reaction with PNO is (2,3-, 2,4-)>3,5->3,4-≫2,6-Cl 2C 6H 3COCl, whereas it is 3,5->(2,3-, 3,4-)>2,4-Cl 2C 6H 3COCl in the PNO-catalyzed two-phase reaction of Cl 2C 6H 3COCl and the corresponding Cl 2C 6H 3COONa. The order of reactivities of Cl 2C 6H 3COO − ions towards the reaction with 1-(benzoyloxy)-pyridinium (C 6H 5COONP +) ion is (3,4-, 3,5-)>(2,3-, 2,4-Cl 2C 6H 3COO −).