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.