ACIDITY OF EXHAUSTIVELY SUBSTITUTED PARA-NITROSOPHENOLS WITH PYRIDINE SUBSTITUENTS
There are a number of exhaustively substituted nitrosophenols with ester groups and methyl substituents in the ring. Acidity constants values are 5,33-5,64 for this nitrosophenols. In the present work, the values of pKa for the newly synthesized nitrosophenols containing simultaneously alkoxycarbonyl groups and the pyridine substituent in the aromatic ring were determined for the first time. The study was performed spectrophotometrically at a temperature of 25°C in citrate buffer solutions. The dependence of the change in acidity with increase in the alkyl substituent of ester groups is the same for nitrosophenols with methyl groups in the ring and for nitrosophenols with a pyridine substituent. It was found the introduction of a pyridine substituent increases acidity by about an order of magnitude in comparison with the known persubstituted nitrosophenols. This increase in acidity is well explained by the manifestation of a negative mesomeric effect of nitrogen atom. It is possible under the condition of co-planarity of the pyridine and benzene rings.