Zinc Photosensitized Reactions of Ethylene

Abstract

An investigation has been made of the polymerization of ethylene photosensitized by zinc, both resonance lines, 2139A and 3076A, being used. With λ3076 the rate of the reaction is very small, and it is concluded that this is probably due to inefficient quenching. With λ2139 a rapid polymerization occurs. The products of the reaction are propylene, butene, and small amounts of higher hydrocarbons. Acetylene formation is negligible. The rate of polymerization increases rapidly with increasing ethylene pressure. While there is some doubt about the mechanism, the most plausible suggestion seems to be that the initial step is $$\mathrm{Zn}{\text{(4}}^1{P}_1\mathrm{)+}{\mathrm{C}}_2{\mathrm{H}}_4=\mathrm{ZnH}+{\mathrm{C}}_2{\mathrm{H}}_3,$$ and that this is followed by an atom and free radical sensitized polymerization of ethylene.