Hydrogen-oxygen reactions primary process

In all hitherto discussed instances the potentials at which the secondary process occurs, such as the liberation of hydrogen, oxygen or chlorine, were widely different from the potentials corresponding to the primary oxidation or reduction process. Sometimes this is not the case. The reduction potential of reaction SnIV -> Sn11, for example, is so close to the potential of hydrogen deposition that both processes take place even at comparatively low current densities. 

Kondratiev investigated the photochemical oxidation of carbonyl sulfide from room temperature to 100 °C and found the major products to be CO and SO2. Very little solid product was formed. In his experiments, the OCS was dissociated into CO and S by means of a hydrogen discharge lamp. The atomic sulfur formed in the primary process abstracted another S atom from OCS to form CO and S2. The only role of oxygen in the system was, according to Kondratiev, reaction with the S2 thus formed. The complete mechanism he postulated was... 

It is evident from the nature of the products, especially those formed with toluene present, that the photoreaction in weakly acidic medium involves incursion of a radical species. The complete suppression of reactions leading to the above products, in the presence of oxygen, strongly suggests that it is an excited triplet trityl ion which undergoes reaction. It is postulated that the primary photochemical process is the abstraction of a hydrogen atom by the triplet trityl ion to form the radical cation 90, which was proposed as an intermediate in the dimerization reactions carried out in strong acid (Cole, 1970). 

---