An investigation has been made of the mercury (3P1
) photosensitized reactions of ethylene. In addition to hydrogen and acetylene the main products are butene, butane and hexenes. The variation of the rate with the pressure of ethylene suggests that a deactivation process is involved, the initial process being of the type
Polymerization arises largely by a free radical mechanism and butane is formed by the reactions
The mechanism is shown to be consistent with the value found for the quantum yield.