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