Trace gases photochemical production/reactions

Combustion processes are the most important source of air pollutants. Normal products of complete combustion of fossil fuel, e.g. coal, oil or natural gas, are carbon dioxide, water vapour and nitrogen. However, traces of sulphur and incomplete combustion result in emissions of carbon monoxide, sulphur oxides, oxides of nitrogen, unburned hydrocarbons and particulates. These are primary pollutants . Some may take part in reactions in the atmosphere producing secondary pollutants , e.g. photochemical smogs and acid mists. Escaping gas, or vapour, may... 

The first publications dealt with simple alkyloxiranes, The photochemical behavior of oxirane, methyloxirane, and ethyloxirane has been investigated by direct irradiation or mercury-sensitized photolysis. The products formed by cleavage have been analyzed, but the nature of the primary processes has not been touched on. A free-radical mechanism has been proposed. A free-radical chain mechanism has been established on the basis of the products obtained on direct irradiation (254 nm) of pure methyloxirane. Experiments with the aim of clarifying the primary photochemical processes were published recently, with irradiation of methyloxirane in the gas phase at 185 nm. Mainly propanal was obtained with a little acetone and traces of ethanol and propanol. An outline of the reaction mechanism is presented in Eq. 325. 

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