The kinetics of the interaction of peroxy radicals. II. Primary and secondary alkyl peroxy

✍ Scribed by Prakash S. Nangia; Sidney W. Benson

• Publisher: John Wiley and Sons
• Year: 1980
• Tongue: English
• Weight: 656 KB
• Volume: 12
• Category: Article
• ISSN: 0538-8066
• DOI: 10.1002/kin.550120105

✦ Synopsis

Abstract

A chain mechanism is proposed to account for the very rapid termination reactions observed between alkyl peroxy radicals containing α‐C—H bonds which are from 10^4^ to 10^6^ faster than the termination of tertiary alkyl peroxy radicals. The new mechanism is
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with termination by
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. \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm R}\overline {{\rm CHOO}} $\end{document} is the zwitterion originally postulated by Criegee to account for the chemistry of O~3~‐olefin addition. Heats of formation are estimated for \documentclass{article}\pagestyle{empty}\begin{document}$ \overline {{\rm CH}_2 {\rm OO,}} {\rm }\overline {{\rm RCHOO}} $\end{document}, and \documentclass{article}\pagestyle{empty}\begin{document}$ ({\rm C}\overline {{\rm H}_3 )_2 {\rm COO}} $\end{document} and it is shown that all steps in the mechanism are exothermic. The second step can account for (^1^Δ)O~2~ which has been observed. k~1~ is estimated to be 10^9–2/θ^ liter/M sec where θ = 2.303__RT__ in kcal/mole. The second and third steps constitute a chain termination process where chain length is estimated at from 2 to 10. This mechanism for the first time accounts for minor products such as acid and __R__OOH found in termination reactions. Trioxide (step 3) is shown to be important below 30°C or in very short time observations (<10 s at 30°C). Solvent effects are also shown to be compatible with the new mechanism.