Oxidative decarboxylation of cyclohexane monocarboxylic acid as a degenerate branching chain reaction II. Mechanism

Abstract

Based on the experimental results obtained studying the oxidative decarboxylation of cyclohexane monocarboxylic acid and published earlier, a mechanism is suggested, according to which in the thermal oxidation two main chain carrier radicals exist: tertiary and secondary peroxy radicals yielding cyclohexanone as well as hydroxy and keto acids in parallel reaction sequences. Carbon dioxide is formed in both pathways independently. The corresponding hydroperoxide molecules, formed during oxidation, decompose partly into radicals and partly into molecules resulting in degenerate branching and chemiluminescence phenomena, respectively. The rate determining termination is the cross combination process between secondary and tertiary peroxy radicals. The combinatorial generation of the mechanism of the thermal process and its reduction enabled the construction of the sequence network of the formation of products indicating that the primary attack of the hydrogen abstraction (secondary or tertiary) determines the product distribution.

MECHGEN: Computer Aided Generation and Reduction of Reaction Mechanisms

“…Therefore in addition to defining an upper limit for κ, we introduced the formulation of an obvious geometric constraint (based on a suggestion made by Péter Hajdu). 33 In an elementary reaction the bonding electrons are redistributed simultaneously between the atomic centers. Obviously the number of pairs of atoms between which there was no bonding before the reaction, but a new bond is formed, is very limited, since these atoms usually had not been in the vicinity of each other prior to the reaction, and must, therefore, approach their respective pair.…”

“…We have found that the above definition leaves too many overcomplicated reactions in the PM, which are unlikely to occur. Therefore in addition to defining an upper limit for κ, we introduced the formulation of an obvious geometric constraint (based on a suggestion made by Péter Hajdu) . In an elementary reaction the bonding electrons are redistributed simultaneously between the atomic centers.…”