94398-04-6Relevant articles and documents
KINETICS AND MECHANISM OF METHANOLYSIS OF BENZOYL DERIVATIVES OF SUBSTITUTED PHENYLUREAS AND PHENYLTHIOUREAS
Kavalek, Jaromir,El Bahaie, Said,Sterba, Vojeslav
, p. 2103 - 2110 (2007/10/02)
The methanolysis rate constants and dissociation constants have been measured of benzoyl derivatives of substituted phenylureas and phenylthioureas.The dissociation constants of the thio derivatives are higher by 1 order of magnitude and the rate constants are higher by 2 orders of magnitude than the respective values of the oxygen analogues.Logarithms of the rate and dissociation constants have been correlated with Hammett ? constant; the ρ constant of the methanolysis of the oxygen derivatives is almost 2 * higher than that of the thio derivatives, which is explained by a change in the rate-limiting step.Methylation of the phenyl nitrogen atom increases the acidity by almost 2 orders of magnitude.This effect is due obviously to steric hindrance to the conjugation with the adjacent carbonyl or thiocarbonyl group.
