Ab initio investigation of O3 addition to double bonds of limonene

The reaction of the O₃ addition to double bonds of the limonene in the gas phase has been investigated using ab initio methods. Four different possibilities for the O₃ addition to the double bonds, which correspond to the two C–C double bonds (endocyclic or exocyclic), and two different orientations of each C–C double bonds, have been considered. The corresponding rate constants have been calculated using the transition-state theory (TST) at the CCSD(T)/6-31G(d) + CF//B3LYP/6-311+G(d,p) level of theory. The high-pressure limit of the overall rate constant at 298 K is found to be ∼2.92 × 10⁻¹⁶ cm³ molecule⁻¹ s⁻¹ that is in a good agreement with the experimental data, and the rate constants of the four individual reaction channels turn out to be 2.1 × 10⁻¹⁶ cm³ molecule⁻¹ s⁻¹, 1.2 × 10⁻¹⁷ cm³ molecule⁻¹ s⁻¹, 6.5 × 10⁻¹⁷ cm³ molecule⁻¹ s⁻¹ and 5.1 × 10⁻¹⁸ cm³ molecule⁻¹ s⁻¹ for 1-endo, 2-endo, 1-exo and 2-exo, respectively.