Theoretical study of Δ-3-(+)-carene oxidation

Abstract

In this work, the rate-limiting steps of Δ³-carene oxidation by ozone and OH radicals were studied. The thermochemical and kinetic parameters were evaluated using the B3LYP, PBE1PBE and BHandHLYP functionals, coupled cluster methods and the 6-311G(d,p) and 6-311++G(d,p) basis sets. The attack on the double bond may occur in different orientations, leading to different oxidation products. The rate coefficients of each step of the reactions were evaluated using conventional canonical transition-state theory and variational canonical transition-state theory whenever necessary. The theoretical rate coefficient for the ozonolysis mechanism, evaluated at the CCSD(T)/6-31G(d,p)//PBE1PBE/6-311++G(d,p) level, was 2.08 × 10⁻¹⁷ cm³ molecule⁻¹ s⁻¹. The coefficient for the oxidation initialised by the OH radical, calculated at the BHandHLYP/6-311++G(d,p) level, was 5.06 × 10⁻¹² cm³ molecule⁻¹ s⁻¹. These values are in reasonable agreement with the experimental results. The importance of these reactions in atmospheric chemistry is discussed.