Reaction of stabilized Criegee intermediates from ozonolysis of limonene with sulfur dioxide: ab initio and DFT study.

The mechanism of the reaction of the sulfur dioxide (SO2) with four stabilized Criegee intermediates (stabCI−CH3−OO, stabCI−OO, stabCIx−OO, and stabCH2OO) produced via the ozonolysis of limonene have been investigated using ab initio and DFT (density functional theory) methods. It has been shown that the intermediate adduct formed by the initiation of these reactions may be followed by two different reaction pathways such as H migration reaction to form carboxylic acids and rearrangement of oxygen to produce the sulfur trioxide (SO3) from the terminal oxygen of the COO group and SO2. We found that the reaction of stabCI−OO and stabCH2OO with SO2 can occur via both the aforementioned scenarios, whereas that of stabCI−CH3−OO and stabCIx−OO with SO2 is limited to the second pathway only due to the absence of migrating H atoms. It has been shown that at the CCSD(T)/6-31G(d) + CF level of theory the activation energies of six reaction pathways are in the range of 14.18−22.59 kcal mol−1, with the reaction betwe...