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Based on the suggested five reaction schemes, nine rate equations (containing one to three parameters to be determined directly) are deduced to describe ab initio initiated nonbranched-chain processes of the saturated free-radical addition to the double molecular bonds using quasi-steady-state treatment. These equations provide good fits for the nonmonotonic (peaking) dependences of the formation rates of the molecular products (1:1 adducts) on the concentration of the unsaturated component in binary systems consisting of a saturated component (hydrocarbon, alcohol, etc.) and an unsaturated component (alkene, allyl alcohol, formaldehyde, or dioxygen). The unsaturated compound in these systems is both a reactant and an autoinhibitor generating low-reactive free radicals. A similar kinetic description is applicable to the nonbranched-chain process of the free-radical hydrogen oxidation, in which the oxygen with the increase of its concentration begins to act as an oxidation autoingibitor (or an antioxidant).
Perspectives
First simple kinetic equations were obtained to describe ab initio initiated nonbranched-chain processes of the saturated free-radical addition to the double molecular bonds. In the processes of this kind the formation rate of the molecular addition products (1:1 adducts) as a function of concentration of the unsaturated component has a maximum. Five reaction schemes are suggested for this addition processes. The proposed schemes include the reaction competing with chain propagation reactions through a reactive free radical. The chain evolution stage in these schemes involves three or four types of free radicals. One of them is relatively low-reactive and inhibits the chain process by shortening of the kinetic chain length.
Dr Michael M. Silaev
Lomonosov Moscow State University
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This page is a summary of: ChemInform Abstract: Competition Kinetics of the Nonbranched-Chain Addition of Free Radicals to Olefins, Formaldehyde, and Oxygen, ChemInform, April 2012, Wiley,
DOI: 10.1002/chin.201220263.
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