Vacuum-Ultraviolet (147.0 and 123.6 nm) Photolysis of trans- and cis-1,2-Dimethylcyclopropanes

Article abstract of DOI:10.1021/j100442a002

The photochemical decompositions of trans- and cis-1,2-dimethylcyclopropanes were investigated at 147.0 and 123.6 nm with standard rare gas resonance lamps.The observed products in the scavenged photolysis system were hydrogen, propylene, acetylene, ethylene, 1,3-butadiene, trans- or cis-2-butenes, pentadienes, allene, methylacetylene, and 1,2-butadiene, listed in decreasing importance.Quantum yields for each of the products were determined in experiments performed in both the presence and the absence of additives.Nitric oxide and oxygen were employed as radical scavengers, whereas hydrogen sulfide and hydrogen iodide were used as radical interceptors.Four radical species were identified and quantified, including methyl, vinyl, allyl, and a mixed C4H7 system.In both systems, ten primary processes have been proposed and the quantum efficiencies assigned for each primary reaction channel.The quantum efficiency for the methylene elimination channel ranged between 0.07 to 0.10 for both systems at both wavelengths. trans-1,2-Dimethylcyclopropane led exclusively to the trans-2-butene, whereas the cis- produced only the cis-2-butene.