Investigation of intermolecular proton exchange of 3,6-di-tert-butyl-2-oxyphenoxyl with N-phenylanthranilic acid by ESR spectroscopy method In this work we studied the intermolecular proton exchange (IPE) reaction between the spin probe of 3,6-ditert-butyl-2-hydroxyphenoxyl (I) and the aromatic amino acid N-phenylanthranilic acid (N-PhAA). The experimental spectra of the 3,6-di-tert-butyl-2-hydroxyphenoxyl-N-phenylanthranilic acid system were recorded using dynamic EPR spectroscopy. The studies were carried out in a non-aqueous indifferent solvent toluene in a wide temperature range. The theoretical EPR spectra of the radical IN -PhAA system corresponding to various process rates were successfully simulated using the ESR-EXHANGE program. This program is written in the modern version of the algorithmic language Fortran 90. The general line-form equation for the four-jump model have been derived from the modified Bloch equations. The second-order rate constants for the intermolecular proton exchange process between radical I and N-PhAA were determined by comparison of the experimental and simulated EPR spectra. The iterative least squares procedure was used for computer analysis of the kinetic data of intermolecular proton exchange and for obtaining activation parameters of the reaction. From kinetic data it follows that N-phenylanthranilic acid has the lowest value of protolytic ability in comparison with aminobenzoic acids.

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The article highlights the creative path of A.S. Masalimov, an outstanding Kazakhstan chemist who celebrates his 70th anniversary in 2022. The main stages of his career and significant events of his scientific career are presented here. The contribution of professor A.S. Masalimov in the foundation and development of the school of ESR spectroscopy and quantum chemistry at the Karaganda Buketov University is shown.

A theoretical study of proton transfer dynamics in complexes of some substituted benzoic acids with 3,6-di-tert-butyl-2-hydroxyphenoxyl (DTBPO) radical is presented. To elucidate the transfer mechanism, reaction pathways for various complexes of benzoic acid derivatives with DTBPO were modeled. The calculations were performed by the DFT method at the UB3LYP/6-31G+(d, p) level of theory using QST3, IRC proce-dures, in vacuum and toluene medium (PCM solvation model). Geometric and kinetic parameters of com-plexes with o-, p-, and m-isomers of nitrobenzoic and chlorobenzoic acids were calculated. Theoretically es-timated activation barrier of 29-30 kJ/mol turned out to be approximately 30 % higher than the previously ob-tained experimental data. It was noted that in the case of o-isomers of aromatic acids the coplanarity of the transition state structure is violated, in contrast to the initial state. This leads to a change in the proton transfer mechanism. The dynamics of charge distribution, dipole moment and electrostatic potential in the studied complexes were analyzed. Based on the calculated data, it was shown that the studied intermolecular proton exchange process occurs throughout Hydrogen Atom Transfer (HAT), and not throughout Proton-Coupled Electron Transfer (PCET) mechanism.

The investigations of acid-base properties of the several small molecules by quantum chemical methodsThe values of ionization potentials calculated for several hydrides and fluorides were obtained by UHF 3-21, UHF 3-21+G and UHF 3-21++G ab initio methods. Quantum chemical calculations show that protonation reactions of the four-atomic hydrides of nitrogen subgroup elements give cations with tetrahedron geometry. Protonation reaction of molecules of the boron subgroup elements follow form with undefined structure.