Alkenes are commonly found in gasoline, naphtha fuels, and biodiesel fuels (fatty acid methyl esters).  In addition, the oxidation of alkenes at low temperature leads to hydroxyalkyleperoxy radicals, which are important intermediates in the oxidation of alcoholic fuels. Therefore, a deeper understanding of alkene oxidation is of increasing importance. This study investigates the oxidation mechanism of all two, three and four carbon mono-unsaturated alkenes using the CBS-QB3 and G4 composite methods. High pressure rate expressions are determined using ChemRate. Following the OH, and subsequent O2, addition onto the double bond, the resulting hydroxyalkylperoxy radicals are found to be significantly influenced by intramolecular H-bonding between the hydroxy and peroxy groups. These intramolecular H-bonds are found to affect the stability of the reactants, products and transition states. The result is that the location of the hydroxy group influences the viability of the various possible reaction pathways, not only at the a-C, to which it is bound, but also the �-, ?- and d-C sites. Under certain conditions, this effect can even reduce the barrier for the 1,4 H-migration reactions to be below the more traditionally favored concerted eliminations. These results are of particular importance to combustion modeling.

Computational study of C2-C4 alkene oxidation

248th National Meeting (2014)

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