Formation of secondary ozonides in the gas phase low-temperature ozonation of primary and secondary alkenes
Abstract
The gas-phase ozonation of a series of alkenes RCHCH2 (R = Et, Hex), trans-RHCCHR (R = Me, Et, Pri) and Me2CCMe2 at –40 to 20 °C, and that of ethene H2CCH2 at –120 to 0 °C at 10–4 v/v concentrations in N2 at atmospheric pressure have been studied. Using complementary product analysis by means of GC–FTIR and GC–MS techniques, we present conclusive evidence for the formation of secondary alkene ozonides as high-yield products in all instances except Me2CCMe2. It is shown that the stereoselectivity for the conversion of trans-RHCCHR (R = Me, Et, Pri) to trans-secondary ozonides in the gas phase is similar to that observed earlier in solution, and that the yields of secondary ozonides from RHCCH2, but not those from RHCCHR, significantly decrease with increasing temperature.