A theoretical investigation of OH formation in the gas-phase ozonolysis of E-but-2-ene and Z-but-2-ene

The energetics and structures of reactants, intermediates, transition states and products in the reactions of ozone with E- and Z-but-2-ene have been calculated using ab initio methods (MP2/6-31G*). Clear differences between the structures of the E- and Z-ozonides are revealed, as well as the existence of two conformers of the Z-isomer. The energies of the transition states between the primary ozonides and the decomposition products (acetaldehyde and methylcarbonyl oxide) indicate differences in the yields of the syn- and anti-forms of the carbonyl oxide from the two isomers of but-2-ene. The results are discussed with reference to the higher hydroxyl radical yields measured in the gas-phase ozonolysis of E-but-2-ene compared to Z-but-2-ene.