Electric discharge, reactive intermediates

Free radicals, however, are often important intermediate products in chemical reactions. Very reactive free radicals can be produced in electric discharges through gases, by the action of radiation, or at high temperatures in flames. All these methods produce a situation of high energy, sufficient to break a covalent bond. Two radicals are then the temporary results... 

Compounds containing silicon bonded to only one other atom are unstable and are usually only generated and observed as reactive intermediates of short half-life. Silicon compounds subjected to flash photolysis or electrical discharges in the gas phase produce short-lived species SiX (X = H, F, Cl, Br, I, C, Si, etc.), the band structure of which have been studied in detail. The structures, electronic configurations, and so on of Six (X = H, F, Cl, Br, I, N, O, etc.) have also been the subject of MNDO (modified neglect of diatomic overlap) and other calculations. ... 

Both ionic and free radical mechanisms can be written to explain the foregoing reactions in more detail, but these would be strictly speculative, since no definitive experimental evidence has been obtained. Some sort of benzene ion must form as a result of inelastic collisions between the electrons and benzene molecules in the plasma, but whether these ions or some derivative species are the reactive intermediates is not known. Recently, Potter et al. (11) have shown that styrene, when perfectly dry, does polymerize via an ionic mechanism when irradiated with gamma rays. One can picture a similar mechanism occurring in the electrical discharge. 

The idea that the formation of reactive products or intermediates in the solution causes explosion is difficult to test experimentally. Future experiments should be designed to test the relative importance of this kind of process against the electrical discharge mechanism. 

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