Reactions of microwave-generated O(3P) atoms with unsaturated hydrocarbons

The reactions of neat olefins or solutions of olefins in acetone at low temperature with oxygen atoms were examined. O(P-3) atoms were produced by microwave irradiation of He/O-2 mixtures, followed by contact of the plasma with the fluid at low pressure and temperature. Addition of oxygen atoms to olefins results in skeletal rearrangements involving hydrogen and alkyl migration reactions and ring rearrangements of the intermediate oxygen adducts in competition with epoxide formation. While epoxide formation predominates for simple olefins such as 1- and 4-octene with minor yields of rearrangement products, for highly substituted or strained olefins, such as norbornadiene, skeletal rearrangement dominates following oxygen atom addition, When oxidation of norbornadiene is carried out in the presence of a radical inhibitor to suppress secondary oxidation leading to benzene, the novel ring-rearrangement product, bicyclo[3.(2,3)1.0]hex-3-ene-endo-6-carboxaldehyde, is produced from norbornadiene in significant yields.