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

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 10⁴ to 10⁶ faster than the termination of tertiary alkyl peroxy radicals. The new mechanism is equation image with termination by equation image . \documentclass{article}\pagestyle{empty}$ {\rm R}\overline {{\rm CHOO}} $ is the zwitterion originally postulated by Criegee to account for the chemistry of O₃‐olefin addition. Heats of formation are estimated for \documentclass{article}\pagestyle{empty}$ \overline {{\rm CH}_2 {\rm OO,}} {\rm }\overline {{\rm RCHOO}} $ , and \documentclass{article}\pagestyle{empty}$ ({\rm C}\overline {{\rm H}_3 )_2 {\rm COO}} $ and it is shown that all steps in the mechanism are exothermic. The second step can account for (¹Δ)O₂ which has been observed. k₁ is estimated to be 10^9–2/θ liter/M sec where θ = 2.303RT 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 ROOH 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.