Search

Hydrolysis of 2,4-dithiophenobarbital in aqueous solutions of pH 2-12 was investigated at 40 and 60 degrees C using UV spectrophotometry. The values of reaction order, rate constants, pKa1 and pKa2 and activation energy were determined. The preliminary estimation of degradation products was accomplished using thin layer chromatography. The major products were isolated by circular chromatography and identified by spectroscopic and classical methods.

Lipophilicty of 29 thiobarbituric acid derivatives were assessed by reversed-phase thin-layer chromatography using methanol: water mixtures as a mobile phase. A linear relationship was found between RM values and methanol concentrations in the mobile phase. The retention parameter, RM0, was related to theoretical partition coefficients calculated by means of different theoretical procedures (AlogPs, IAlogP, miLogP, logPKowwin, xlogP).

The rates of hydrolysis of thiophenobarbital and its N-mono- and N,N'-dimethyl-derivatives were determined under different conditions of pH and temperature using UV spectroscopy. They were compared with those obtained in the presence of different concentrations of beta-cyclodextrin. It was found that the compounds degrade with different rates and beta-cyclodextrin retards the hydrolysis. The formation of complexes between the investigated compounds and beta-cyclodextrin was proved by 13C NMR and ROESY spectra and molecular modeling. The inclusion with the phenyl substituent into the beta-cyclodextrin cavity is preferred.

Kinetics of hydrolysis of N,N- and N,S-dimethyl-2-thiophenobarbital and products of this reaction were investigated. The UV spectroscopy served as a tool for kinetic investigations and chromatography was used to separate and isolate the main products of hydrolysis. These products were identified by spectroscopic methods and the course of hydrolysis of both isomers was compared.