No abstract

One of the possible directions of liquid-phase oxidation of α-pinene by atmospheric oxygen leads to the formation of a mixture of terpene oxygen-containing compounds (epoxides, alcohols, ketones, etc.). The problem of this direction is the formation of a large amount of 2,3-epoxypinane which over time turns into trans-sobrerol, campholene aldehyde, trans-pinocarveol, trans-carveol, and trans-3-pinen-2-ol as a result of hydrolysis. One of the abovementioned substances with a solid crystalline structure is trans-sobrerol. Sobrerol is widely used in perfumery for synthesis of synthetically fragrant substances and pharmaceutical industry, in particular, it is a part of medicines with mucolytic action, as well as in the treatment of headaches and diseases such as rhinorrhea and chronic bronchitis. The aim of this work is to identify a crystalline product produced by liquid-phase oxidation of α-pinene with atmospheric oxygen in the presence of cobalt (II) stearate. The process of liquid-phase oxidation was carried out in the following conditions: temperature – 70 °С, air consumption – 16.67 cm3/s, duration – 5 h, amount of catalyst – 0.2–0.5 wt.%. Then the mixture was exposed to steam distillation in order to separate monomers (they contain terpene oxygen-containing compounds and hydrocarbons) from polymers. As a result of settling and storage of the mixture, crystals were found and isolated from the mother liquor solution. Their identification was carried out using IR and 13C NMR spectroscopy as well as scanning electron microscopy. It was found that the spatial organization of the isolated crystals and the standard sample (Sigma Aldrich) is represented by multilayer rectangular plates. Analysis of the IR spectra of the crystals showed that the absorption band at a wave number of 3318 cm–1 corresponds to intramolecular and intermolecular hydrogen bonds in hydroxyl groups, at wave numbers of 2887, 2935, 2975 cm–1 it corresponds to methyl groups. The results obtained are comparable with the results of the IR-spectrum of the standard sample. Given the results of previous studies of 1H NMR spectrum [15] and 13C NMR spectrum, it was determined that the resulting crystalline product of liquid-phase oxidation of α-pinene is trans-sobrerol.

The effectiveness of several synthetic and natural antioxidants (AO) in inhibiting the oxidation of linseed oil has been studied. Under the conditions of accelerated oxidation at 100 °С, the values of the induction period of oxidation and stabilization factors of linseed oil in the presence of additives of known phenolic AOs, tocopherols, fat-soluble ascorbic acid esters and compositions based on them were determined. The data obtained indicate that ascorbic acid esters effectively inhibit the oxidation of linseed oil. The stabilizing effect of ascorbyl palmitate (AP) increases with an elevation in the content of α-linolenic acid in the oil and a decrease in the oxidative stability of the oil. One AP provided better stabilization efficiency than some known compositions based on it. Kinetic data on the accumulation of oxidation products in linseed oil with AP additives during the storage at room temperature and with free access of the air were obtained, demonstrating high inhibiting activity of AP under these conditions, which provides a possibility to increase the shelf life of the stabilized oil up to 18 months or more.