USING MATHEMATICAL MODELING TO EVALUATE THE ANTIOXIDANT ACTIVITY OF S-, Se-CONTAINING SPATIALLY HINDERED PHENOLS

In this work, regression analysis was used to evaluate the antioxidant activity of the synthesized S- and Se-containing α-methylbenzylbisphenols in comparison with the industrial antioxidant additive 2,6-ditretbutyl-4-methylphenol under similar conditions. The experimental antioxidant efficiency was calculated from the ratio of the peaks of chemiluminescent glow in vaseline oil at concentrations of 0.025–1% at 200 °C. Based on the results of calculations and experimental data, numerical dependences of the influence of concentrations – x1 (% wt.conc.), electrophilicity x2 on the antioxidant capacity (Y) of the studied additives to lubricating oils and cutting fluids were constructed in the form of nonlinear equations. The behavior of the studied compounds is analyzed and modeled, taking into account the geometric parameters of the molecules for the property under study, depending on the mass concentration. According to the research results, it was confirmed that the introduction of a methyl group into the p-position of the benzene ring of hindered phenol leads to an increase in antioxidant efficiency. The numerical method shows the effectiveness of the use of these additives in comparison with the widely used additive "Agidol-1". The obtained values of the structural parameters of the compounds calculated by the UB3LYP/6-311++G(d,p) method agree with the experimental data (with an accuracy of 81%-98.7%). The effectiveness of sterically hindered phenols is due to the presence of bulky substituents in the o-positions, which optimally shield the hydrogen of the OH group and, accordingly, the low activity of the phenoxyl radical formed in the reaction with peroxide radicals from the inhibitor. The clearly presented dependences show that Se-containing derivatives of α-methylbenzylphenol exhibit greater antioxidant efficiency and are effective inhibitors of lubricating oils and cutting fluids due to the presence of a larger number of active sites in these molecules and, therefore, interrupting a greater number of oxidation chains than molecules with a disulfide bridge.