title: Structure-reactivity relationships in the pyridinolysis of N-methyl-N-arylcarbamoyl chlorides in dimethyl sulfoxide.
abstract: Nucleophilic substitution reactions of N-methyl-N-arylcarbamoyl chlorides (YC(6)H(4)N(CH(3))COCl) with pyridines (XC(5)H(4)N) have been investigated in dimethyl sulfoxide at 45.0 degrees C. A striking trend in the selectivity parameters is that they are constant within experimental errors, rho(X) = -2.25 +/- 0.03, beta(X) = 0.42 +/- 0.01, and rho(Y) = 1.10 +/- 0.06, with changing reactivities of the electrophiles (deltasigma(Y)) and nucleophiles (deltasigma(X)), respectively, and this leads to a vanishingly small cross-interaction constant, rho(XY) approximately equals beta(XY) approximately equals 0. The rate data can be expressed in the Ritchie N(+) type equation. Based on this and other results, the mechanism of nucleophile (pyridine) addition to the resonance- stabilized carbocation is proposed. It has been shown from the definition of beta(XY) (and rho(XY)) together with the Marcus equation that the high intrinsic barrier, DeltaG(0), in the intrinsic-barrier controlled reaction series is a prerequisite for such reactions in which the cross-interaction vanishes and the N(+) relationship holds.
authors.affiliation: Department of Chemistry, Inha University, Inchon, 402-751 Korea. ilee@inha.ac.kr
authors.forename: I
authors.initials: I
authors.lastname: Lee
authors.forename: S W
authors.initials: SW
authors.lastname: Hong
authors.forename: H J
authors.initials: HJ
authors.lastname: Koh
authors.forename: Y
authors.initials: Y
authors.lastname: Lee
authors.forename: B S
authors.initials: BS
authors.lastname: Lee
authors.forename: H W
authors.initials: HW
authors.lastname: Lee