Abstract
A kinetic study of the reactions of potentially bioactive 2-amino-4-arylthiazoles with highly reactive 4,6-dinitrobenzofuroxan (DNBF) is reported herein in acetonitrile solution. The complexation reaction was followed by recording the UV-vis spectra with time at lambda(max )= 482 nm. Electronic effects of substituents influencing the rate of reaction have been studied using structurereactivity relationships. It is shown that the Hammett plot relative to the reaction of DNBF with 2-amino-4-(4-chlorophenyl)thiazole exhibit positive deviation from the log k(1) versus c correlation, while it showed excellent linear correlation in terms of Yukawa-Tsuno equation. It has be noticed that the nonlinear Hammett plot observed for 2-amino-4-(4-chlorophenyl) thiazole is not attributed to a change in rate-determining step but is due to nature of electronic effect of substituent caused by the resonance of stabilization of substrates. The second-order rate constant (k(1)) relating to the bond C-C and C-N forming step of the complexation processes of DNBF with 4-substituted-aminothiazoles and 2-amino-5-methyl-4-phenylthiazole, respectively, is fit into the linear relationship log k = S-N (N + E), thereby permitting the assessment of the nucleophilicity parameter (N) of the 2-amino-4-arylthiazoles of the range (4.90 < N < 6.85). 2-amino-4-arylthiazoles is subsequently ranked by positioning its reactivity on the general nucleophilicity scale developed recently by Mayr and coworkers (2003) leading an interesting and a direct comparison over a large domain of pi-, sigma-, and n-nucleophiles. The global electrophilicity/nucleophilicity reactivity indexes of the 2amino-4-arylthiazoles have been investigated by means of a density functional theory (DFT) method. . (C) 2020 The Authors. Published by Elsevier B.V. on behalf of King Saud University.