ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

4-substituted 2-nitrophenylguanidines .3. Kinetic-study of the cyclization

P. Pazdera, J. Pichler, and M. Potáček

Department of Organic Chemistry, Faculty of Natural Sciences, J. E. Purkyně University, CS-611 37 Brno

Abstract: The rate of cyclization of 4-X-2-nitrophenylguanidines to 3-amino-7-X-1,2,4-benzotriazine-l -oxides was searched in dependence on pH and substituent X by spectrophotometry. The cyclization was found to be an irreversible reaction. The rate con­stant was shown to be a linear function of the hydroxide ion concentration. The values of the logarithm of rate constant of cyclization of the individual 4-substituted 2-nitroguanidines are in good correlation with Hammett  σ_m constants of substituents X. The dependence of the reaction rate on the guanidine concentration and on the temperature of reaction was investigated for the derivative with X = OCH₃. It was proved that the reaction is of the first order with respect to substrate. The energy of activation and the frequency factor were cal­culated from the dependence of the reaction rate on temperature and from Arrhenius equation. The entropy and the enthalpy of activation were cal­culated from Eyring equation.

Full paper in Portable Document Format: 424a547.pdf

Chemical Papers 42 (4) 547–558 (1988)