Influence of the topology of molecules on the sorption of derivatives of 1,2,4-triazole and 1,2,4-triazine by nonpolar sorbents under conditions of liquid chromatography

Abstract

The article is devoted to investigation of 1,2,4-triazine and 1,2,4-triazole derivatives chromatographic behavior. The purpose of this work was to study the regularities of some 1,2,4- triazine and 1,2,4- triazole derivatives sorption from water – acetonitrile solutions on different nature sorbents under condition of reversed-phase high performance liquid chromatography. Octadecyl silica gel (ODS), porous graphitized carbon (PGC) and hypercrosslinked polystyrene (HCLP) were used as sorbents. As a result, correlations be- tween topological indices, physico-chemical characteristics, and retention factors of these compounds were obtained. As it was shown, the main factors influencing the properties of the triazole and triazine derivatives studied by us are the presence and number of heteroatoms, the nature of the substituents and their position, which to a large extent also determine the topology of the molecules. The analysis of the correlations showed that, in general, connectivity indices (ICs) of all five orders correlate well with the 1,2,4-triazole and 1,2,4- triazine, 1,3-benzoxazole derivatives with parameters characterizing the dispersion interactions. The maxi- mum values of the correlation coefficient are characteristic for zero-order correlations of the linkage index, the minimum values for the third order 3χ. The values of the Wiener index (IV) in the series of heterocycles investigated increase monotonically with the increase in the size of the molecules; however, the correlation between the IV and the dimensional parameters of the molecules turns out to be somewhat less rigorous than for the IC. It was found that the replacement of two methyl radicals by two phenyl derivatives of 1,2,4- triazines significantly increases the surface area, molecule volume and topological indices. However, the retention values vary depending on the nature of the sorbent. The likely reason for the apparent discrepancy between the values of the retention factor and the dimensional characteristics of some substances may be the stereochemistry of the molecules, which is not taken into account both in the physicochemical and topological parameters used.