Experimental and theoretical determination of sorption characteristics of 1,2,4-triazole derivatives using liquid chromatography and molecular-statistical modeling

Abstract

Nitrogen-containing heterocyclic compounds has various chemical, physicochemical and biological properties. This determines their wide application as drugs, fungicides, corrosion inhibitors, catalysts. The possibility of attaching structural fragments with various functional groups to a heterocycle allows for targeted synthesis and obtaining substances with desired properties. Such compounds can be considered as model compounds for studying the effect of structure on physicochemical properties. The aim of this work is to establish the relationship between the structural features of 1,2,4-triazole derivatives and their sorption characteristics under HPLC conditions. Porous graphitized carbon was chosen as a sorbent, elution was carried out with water-acetonitrile solutions. The effect of various conditions on retention parameters was studied, the relationship between sorption and physicochemical characteristics was established, experimental values ​​of thermodynamic parameters were determined and compared with theoretical ones.

The derivatives of 1,2,4-triazole were considered, which were ortho- and para-isomers, homologues, contained hydroxyl and carboxyl functional groups. The experiment was carried out on a liquid chromatograph with a spectrophotometric detector. Elution was carried out in an isocratic mode with solutions in which the concentration of acetonitrile was changed from 30 to 80% (vol.) and at three temperatures. To assess the reliability of the correlation dependencies that reflect the relationship between the experimentally obtained sorption and theoretically calculated values of physicochemical parameters, the Pearson correlation coefficient was used.

It is known that under the conditions of reversed-phase liquid chromatography, the sorption process is largely determined by the physicochemical parameters of molecules. It has been established, for example, that an increase in the length of a hydrocarbon radical promotes an increase in the numerical values ​​of lipophilicity and polarizability, and this leads to an increase in the contact time of molecules with the sorbent surface. It is shown that in the presence of polar functional groups in triazole derivatives, the compounds are eluted more rapidly from the column, probably due to higher numerical values ​​of the dipole moment. When studying the effect of temperature on retention, it is noted that this process is spontaneous and exothermic, since the values ​​of the Gibbs energy and standard molar enthalpy and entropy are negative. A comparison is made of the Henry constants calculated on the basis of experimental data and those obtained using the molecular statistical modeling method. It is noted that there is an average positive correlation between these values, since the Pearson coefficient lies in the range from 0.25 to 0.49 and is approximately 0.4.