Strong dependence on multistructural anharmonicity of the relative rates of intramolecular H-migration in alkylperoxyl and methylcyclohexylperoxyl radicals

Alkylperoxyl (RO2) and hydroperoxyalkyl (QOOH) species are crucial intermediates produced during the autoignition of transport fuels, consequently their thermodynamic kinetic data very important. Since these not available experimentally, we take up challenge computing them from first principles. We compare 1,5 shifts in 2-methyl-4-heptylperoxyl radical 3-methylcyclohexylperoxy to clarify similarities differences kinetics chain alkanes cycloalkanes fuel oxidation mechanism. In order account multistructural coupled torsional anharmonicity, employ canonical variational transition state theory (MS-VTST) with multidimensional tunneling calculate rate constants. The calculations explicitly include all conformers: 6 154 for two reactants, 7, 6, 1, 1 four states, 289, 282, 8, 5 products (which reactants reverse reactions). effects various factors on calculated constants evaluated detail. found that anharmonicity has a large effect This work illustrates how modern density functional dynamics methods make it possible accurate both branched-chain cycloalkane peroxy radicals hydroperoxy species.