Mutual interactions of the methyl and methylperoxy radicals studied by flash photolysis and kinetic spectroscopy

Abstract The decadic extinction coefficient of the methyl radical at 216.4 nm and the rate constant for mutual combination were redetermined as:\documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{l} \varepsilon (216.4) = (9.5 \pm 0.4) \times 10^3 1./mol\,cm \\ k_2 = (3.2 \pm 0.4) \times 10^{10} 1./mol\sec \\ \end{array} $$\end{document} . The application of the Beer–Lambert law to these measurements was justified experimentally. The absorption spectrum of the methylperoxy radical was characterized as a weak, broad, structureless band, having a maximum at 240 nm with ϵ(240) = 1.55 × 10 3 l./mol cm. The mutual interaction of methylperoxy radicals leads to the generation of methoxy and hydroperoxy radicals as a consequence of the nonterminating interaction\documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{l} 2{\rm CH}_{\rm 3} {\rm OO}^{\rm .} \to 2{\rm CH3O}^{\rm .} + {\rm O}_{\rm 2} \\ {\rm CH}_{\rm 3} {\rm O}^{\rm .} + {\rm O}_2 \to {\rm HCHO + HOO}^{\rm .} \\ \end{array} $$\end{document} . Each derivative radical may consume a significant fraction of the methylperoxy radicals, and either of these cross interactions may be made predominant by a suitable choice of oxygen pressure. The mutual interaction was studied under both conditions. The overall mechanism was analyzed by a precise computational method, and the rate constant of the total mutual interaction\documentclass{article}\pagestyle{empty}\begin{document}$$ 2{\rm CH3O}^{\rm .} \to {\rm all}\,{\rm products} $$\end{document}was estimated as\documentclass{article}\pagestyle{empty}\begin{document}$$ k_4 = (3.5 \pm 0.3) \times 10^8 1./mol\sec $$\end{document} .