Hg(3P1) photosensitized reactions of cyclopropane

Abstract

Under static conditions the major reaction product is a polymer. Polymerization is inhibited by free radical scavengers such as NO, O2, butadiene-1,3, etc. with a simultaneous large increase in propylene yields. The NO inhibited reaction affords propenaldoxime and acrylonitrile as principal products, indicating the presence of allyl radicals, and N2O which is indicative of H atoms. Polymerization can also be suppressed by rapid flow: it is entirely a secondary process. The products of the flow experiments are: propylene, biallyl, allylcyclopropane, 4-methyl pentene-1, hexene-1, 2,3-dimethyl butane, C5 and C9 hydrocarbons, H2, CH4, C3H8, and traces of bicyclopropyl. Most of the products can be accounted for by the self-scavenging of H atoms by propylene and the ensuing reactions of isopropyl and allyl radicals. The major primary step is the formation of an electronically excited cyclopropane, possibly the ground state triplet of trimethylene with a large excess of vibrational energy. The primary decomposition is retarded by pressure. Φ(decomp.) > 0.38, at 20 Torr, but is less than unity.