Reactions of Microwave-Generated O(³P) Atoms with Unsaturated Hydrocarbons

Abstract

The reactions of neat olefins or solutions of olefins in acetone at low temperature with oxygen atoms were examined. O(3P) atoms were produced by microwave irradiation of He/O2 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[3.2,31.0]hex-3-ene-endo-6-carboxaldehyde, is produced from norbornadiene in significant yields.

Oxidation of Propylene with Oxygen and Air in a Barrier Discharge in the Presence of Octane

“…An analysis of the literature data [16,17] dealing with the reactions of O( 3 P) with olefin molecules shows that an O( 3 P) atom gets attached to a carbon atom of the double bond. The resulting adduct (alkenoxy radical) is rearranged to form a final product by ring closure (formation of an epoxide) or by migration of a hydrogen atom or an alkyl group from the carbon atom, which is conjugated with O( 3 P), to another carbon atom of the initial double bond (formation of carbonyl compounds).…”

“…On the other hand, the energy of BD electrons spent on excitation of electronic levels of oxygen is decreased, while that deposited into excitation of nitrogen is increased. Thus, it is reaction (17) which provides the most reasonable reaction pathway for the formation of a significant part of atomic oxygen in the original mixture with a nitrogen content of 78 vol% (air model).…”

“…The resulting condensate with the dissolved oxidation products drained down the walls of the reactor as a film into the receiver-flask (16). The receiver flask was cooled to -20°C with a mixture of sodium chloride and ice (17). The reactor walls were thermostatically controlled by a cooling coil (18) attached to the thermostat (19).…”

Microwave Assisted Heterofunctionalization of Alkenes and Alkynes

“…It should also be noted that certain plasmas (prepared by microwave discharge) generate O( 3 P) that oxidizes alkenes [125][126][127][128].…”

Generation of free oxygen atoms O(3P) in solution by photolysis of 4-benzoylpyridine N-oxide

“…Atomic oxygen in its ground triplet state, O( 3 P), is a powerful but selective oxidant for organic substrates. In the gas phase and in solution it reacts with aromatic hydrocarbons 1,2 and alkanes 3,4 to yield alcohols, and with olefins [5][6][7][8][9] to yield epoxides, ketones, and aldehydes. By comparison, hydroxyl radicals, ozone and other reactive oxygen species often react with organic compounds almost indiscriminately and generate an array of oxidized, fragmented and isomerized products.…”