Mercury-Sensitized Photolysis of Propylene Primary and Radical Reactions

A description is given of the mercury-sensitized photolysis of propylene and mixtures of propylene with H2, D2, and propylene-d6 at 26°C using 253.7 and 184.9-nm light. There are at least five primary steps: C3H6*→H+C3H5, C3H6*→CH3+C2H3, C3H6*→cyclopropane, C3H6*→CH4+C2H2, C3H6*→H2+(C3H4).The ratios of the primary reaction rates depend upon wavelength of the light and deuteration of the propylene. Addition of hydrogen atoms to the propylene double bond gives 5% n-propyl radicals. We find no evidence of vinyl—vinyl radical combination to form butadiene. The cross-combination ratio of isopropyl and allyl radicals is 6½.