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Випуск 2(23) >
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| Название: | ОСОБЕННОСТИ РАДИКАЛЬНО-ЦЕПНОГО ОКИСЛЕНИЯ АСКОРБИНОВОЙ КИСЛОТЫ В АПРОТОННОЙ СРЕДЕ |
| Другие названия: | FEATURES OF RADICAL-CHAIN OXIDATION OF ASCORBIC ACID IN APROTIC MEDIA |
| Авторы: | Смирнова, О.В.
Ефимова, И.В.
Опейда, И.А. |
| Ключевые слова: | аскорбиновая кислота
радикально-цепное окисление
кинетика
ascorbic acid
radical chain oxidation
kinetics |
| Дата публикации: | 2014 |
| Издатель: | Наукові праці ДонНТУ. Серія: Хімія і хімічна технологія. - 2014. - Вип. 2(23). - С. 142-148 |
| Аннотация: | Газоволюмометрическим методом изучен процесс инициированного окисления аскорбиновой кислоты кислородом в апротонной среде в гомофазных условиях. Предложена схема инициированного радикально-цепного окисления аскорбиновой кислоты в апротонной среде. |
| Описание: | In recent years, the study of the ascorbic acid (АА) action mechanism obtained important new results, which showed that АА undergoes a reversible redox process with the formation of intermediate free radicals. Unusual biological properties of АА, to protect against free radical destruction, is likely related to the effectiveness of AА as radical scavengers and stability of its radical anion (A•). Radical anion (A•) reacts predominantly with itself and thus stops the development of free-radical reactions. This concept is supported by several studies, which demonstrated that the radical anion A• is a staple in the interaction AА with several redox systems in protic media. However aprotic systems oxidation AK poorly understood. In this connection it is interesting to study the characteristics of the initiated radical chain oxidation of AA in aprotic medium.
In this paper we studied the radical-chain oxidation of AA in dimethyl sulfoxide (DMSO) and chlorobenzene (ChB), аs the initiator used azodiisobutyronitrile (AIBN). The kinetics of the oxidation process was monitored volumetric measuring the amount of oxygen absorbed investigated systems at constant temperature 348 K. It shows typical kinetic curves of oxygen absorption by studied system AIBN - AA - ChB - DMSO. Oxygen absorption rate of the reaction mixture increases with its concentration of AA in the range of 0,01-0,30 mol/l. Obtained a linear dependence of the rate of AA oxidation on time.
Oxidation products identified by NMR-spectroscopic method. 13C NMR spectra were recorded on a Bruker DRX 400 (100 MHz) in DMSO-d6, using the residual solvent signal as internal standard (40,0 ppm for 13C nuclei). The NMR spectroscopic method identified oxidation products of AA in aprotic medium and proved that under these conditions AA oxidized to dehydroascorbic acid (dehydroAA) only.
We propose a scheme initiated radical chain oxidation of ascorbic acid in an aprotic medium. According to this scheme, the oxygen uptake occurs only in reactions with AA and AIBN. This scheme can be supplemented by the equations describing the formation of the radical anion of oxygen and its interaction with AA and ascorbic acid radical (AH•). But we believe it is not appropriate because of the reaction of superoxide anion changes do not account for the absorption of oxygen and therefore not included in the equation for calculating the rate of oxidation of AA. Furthermore, test hydroperoxides which are formed negative. This is due to the loss of hydroperoxide molecules of the solvent. |
| URI: | http://ea.donntu.edu.ua/handle/123456789/26011 |
| Располагается в коллекциях: | Випуск 2(23)
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