Single-Electron Transfer in [sigma]-Complexation Reactions of 2,6-Dimethoxy-3,5-dinitropyridine with Para-X-phenoxide Anions in Aqueous Solution

• Published in: International journal of chemical kinetics Vol. 48; no. 9; p. 523
• Main Authors: Mahdhaoui, Faouzi, Dhahri, Nejeh, Boubaker, Taoufik
• Format: Journal Article
• Language: English; French; German
• Published: Hoboken Wiley Subscription Services, Inc 01.09.2016
• Subjects: Aqueous solutions; Kinetics
• ISSN: 0538-8066; 1097-4601
• DOI: 10.1002/kin.21011

Second-order rate constants have been measured spectrophotometrically for reactions of 2,6-dimethoxy-3,5-dinitropyridine 1 with 4-X-substituted phenoxide anions (X = OMe, Me, H, Cl, and CN) 2a-e in aqueous solution at various temperatures. The effect of phenoxide substituents on the reaction rate was examined quantitatively on the basis of kinetic measurements, leading to nonlinear correlations of [Delta]≠H and [Delta]≠S with Hammett's substituent constants (σ). Each Hammett plots exhibits two intersecting straight lines for the reactions of 1 with the phenoxide anions 2a-e, whereas the Yukawa-Tsuno plots for the same reactions are linear. The large negative ρ values (-4.03 to -3.80) obtained for the reactions of 1 with the phenoxide anions possessing an electron-donating group supports the proposal that the reactions proceed through a single-electron transfer mechanism.