Реактивности 3-N-(4-супституисаних фенил)-5-карбоксиурацилa

The effect of various phenyl substituents on the reactivity of the carboxy groups of 3-N-(4-substituted phenyl)-5-caboxy uracils has been investigated. The substitutents at the phenyl nucleus were as follows: H, Br, I, NO2, Me, OMe. The rate constants of the investigated acids in their reaction with diazodiphenylmethane (DDM) were determined in methanol and in ethanol at 30 °C, using the known spectrophotometric method. The obtained kinetic data, as well as the values of the IR stretching vibrations of the carboxy carbonyl group, were treated by semiempirical relationships based on the principals of linear free energy correlations. Considering that the substituted phenyl group resides at the nitrogen atom, having two carbonyl groups as ortho substituents, it is very probable that the effect of the substituents in position 4 of the phenyl nucleus is influenced by resonance interactions between the nitrogen electron pair, the carbonyl groups and the substituent itself. The polarity of the reaction medium also affects the complex resonance interactions in the molecules of the investigated compounds