Kinetic Studies on Nucleophilic Addition Reactions of 4-X-substituted Anilines to N1-methyl-4-nitro-2,1,3 benzothiadiazolium terafluoroborate in Acetonitrile: Reaction Mechanism and Mayr's Approach

The kinetics of the coupling of N1-methyl-4-nitro-2,1,3 benzothiadiazolium tetrafluoroborate 1 with a series of 4-X-substituted anilines 2a-f (X = OH, OMe, Me, H, Cl, and CN) have been investigated in acetonitrile at 20 degrees C. The second-order rate constants result in a nonlinear Bronsted-type plot. The Hammett plot is also nonlinear, whereas the Yukawa-Tsuno plot exhibits an excellent linear correlation with = -1.62 and r = 1.44. The large Bronsted ((nuc) = 1.24) and Hammett ( = -5.16) values suggest that the reactions proceed trough a single electron transfer mechanism. The finding of satisfactory correlation between the log k(1) of the reactions and the oxidation potentials (E degrees) of anilines 2a-d supports this mechanism. On the other hand, electrophilicity parameter E of benzothiadiazolium cation 1 as defined by the correlation log k(20 degrees C) = s(E + N) has been determined and compared with the electrophilic reactivities of a large variety of electrophiles. (C) 2015 Wiley Periodicals, Inc.