Computational investigations of singlet biradicals: Concerted and stepwise mechanisms for reactions of ozone with acetylene, butadiene and isoprene

Broken Symmetry Unrestricted Density Functional Theory (BSUDFT) has been employed to investigate the stepwise reaction pathways of the following three ozone reactions: (1) Ozonolysis of Acetylene. A three-step reaction pathway has been described along with the conventional concerted reaction pathway. The stepwise reaction pathway as the dominant or an important reaction mechanism for this reaction is suggested. (2) Ozonolysis of Butadiene. The concerted and stepwise reaction pathways to form the primary ozonides, the concerted and stepwise reaction pathways to form formaldehyde or acrolein and carbonyl oxides through the decomposition of primary ozonides, and the formation of an epoxy compound before the formation of primary ozonide are investigated in this study. (3) Ozonolysis of Isoprene. The A factor, the rate constant and the activation energy derived from a stepwise path to form the primary ozonide are in excellent agreement with experiment. Stepwise reaction pathways to form primary ozonides and carbonyl oxides (through decomposition of primary ozonides) have advantages over the concerted reaction pathways.