Updating the Chemiluminescence Oxygen‐Aftereffect Method for Determining the Rate Constant of the Peroxy‐Radical Self‐Reaction: Oxidation of Cyclohexene

• Published in: Photochemistry and photobiology 2019-05, Vol.95 (3), p.780-786
• Main Authors: Fedorova, Galina F., Lapina, Viktoryia A., Menshov, Valery A., Naumov, Vladimir V., Trofimov, Aleksei V., Tsaplev, Yury B., Vasil'ev, Rostislav F., Yablonskaya, Olga I.
• Format: Article
• Language: English
• Subjects: Chains; Chemiluminescence; Computer simulation; Cyclohexene; Hydrocarbons; Kinetics; Mathematical models; Organic chemistry; Oxidation; Oxidation process; Oxygen; Peroxy radicals; Radicals; Reaction kinetics; Substrates
• ISSN: 0031-8655; 1751-1097
• DOI: 10.1111/php.13058

Updating the facile chemiluminescence oxygen‐aftereffect method, most suitable for determining the rate constant (kt) of the peroxy‐radical self‐reaction (main chemiluminescence channel), pertained to considering the sensitivity of such a method toward a disturbing influence of the peroxy radicals of the initiator of the chain oxidation process. Such a disturbance may derive from the side chemiluminescent reaction, which involves peroxy radicals of both hydrocarbon and initiator. To examine the applicability and limitations of the chemiluminescence method under present scrutiny, cyclohexene was used as the model oxidizable hydrocarbon substrate. Computer simulations of the reaction and chemiluminescence kinetics have demonstrated the validity of the considered methodology at the value of the rate constant of the propagation of the overall chain process by peroxy radicals of the initiator higher than 1 m−1 s−1. Despite that the chemiluminescence time profile and the stationary level of the total chemiluminescence intensity depend on the kinetics of the side chemiluminescence channel and on the ratio of the excited‐state generation yields in the mentioned reaction channel and in the main chemiluminescence process, the value of kt assessed by the oxygen‐aftereffect method has been found independent of variation of these characteristics. Upon a fast admission of oxygen to a deoxygenated solution of a hydrocarbon to be oxidized and an initiator of the chain oxidation process, the intensity (J) of chemiluminescence emission rises from zero to its stationary level. The time profile of the light intensity, J(t), serves for acquiring the value of rate constant kt of the peroxy‐radical self‐reaction. The validity of this experimental approach has been demonstrated through computational modeling of the reaction kinetics upon the variation of the rate constants of the elementary steps of the chain oxidation process in the range of two orders of magnitude.