title: Nucleophilic substitution reactions of alpha-chloroacetanilides with benzylamines in dimethyl sulfoxide.
abstract: Kinetic studies of the reactions of alpha-chloroacetanilides (YC6H4NRC(=O)CH2Cl; R = H (5) and CH3 (6)) with benzylamines (NH2CH2C6H4X) were carried out in dimethyl sulfoxide at 55.0 degrees C. The Brønsted betaX values were in the range from 0.6 to 0.9 and cross-interaction constants phoXY were positive: phoXY = +0.21 and +0.18 for 5 and 6, respectively. The rates were faster with 6 than with 5 and inverse secondary kinetic isotope effects involving deuterated benzylamine (ND2CH2C6H4X) nucleophiles, kH/kD < 1.0, were obtained. Based on these and other results, a stepwise mechanism with rate-limiting expulsion of the chloride leaving group from a zwitterionic tetrahedral intermediate, T+/-, is proposed. In this mechanism, a prior carbonyl addition to T+/- is followed by a bridged type transition state to expel the chloride. An enolate-like transition state in which the developing negative charge on C(alpha) delocalizes toward the carbonyl group (nC-->pi*(C=O) interaction) is not feasible for the present series of reactions due to a stronger charge transfer involving the lone pair on the anilino nitrogen (nAN-->pi*(C=O) interaction).
authors.affiliation: Department of Chemistry, Inha University, Inchon 402-751, Korea.
authors.forename: Ki Sun
authors.initials: KS
authors.lastname: Lee
authors.forename: Keshab Kumar
authors.initials: KK
authors.lastname: Adhikary
authors.forename: Hai Whang
authors.initials: HW
authors.lastname: Lee
authors.forename: Bon-Su
authors.initials: BS
authors.lastname: Lee
authors.forename: Ikchoon
authors.initials: I
authors.lastname: Lee