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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  σm 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)

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