Mass Spectra and Pyrolyses of Some Vinylene Carbonates

Article abstract of DOI:10.1021/jo00343a020

The mass spectra of a series of 1,3-dioxol-2-ones were examined for evidence of oxirenes in the fragmentation process.The M-cation radical-CO2 (oxirene or isomers) fragment was observed in six of eight samples.Four major pathways explain the mass spectra: M-cation radical-CO2-CO, M-cation radical-C2O3, M-cation radical-C2O2R and M-cation radical-CO-CO2.Metastable peaks support this.Similar pathways on pyrolysis were sought and observed.At 800 deg C and pressure of 1.5-4 mm, 1,3-dioxol-2-ones 1-3 and 5-7 were pyrolyzed in a stream of helium.The major products were, respectively, ketene (R₁=R₂=H), propene (R₁=R₂=CH3), fluorene (R₁=R₂=C6H5), ethene (R₁=H, R₂=CH3), stilbene (R₁=H, R₂=C6H5), and styrene (R₁=CH3, R₂=C6H5).Apparently the 1,3-dioxol-2-ones lose CO2 and CO successively to produce a carbene which either rearranges or dimerizes.