Photolysis of Cyclopropane at 1470 and 1634 Å

The vacuum-ultraviolet photolysis of cyclopropane in the gas phase has been investigated at room temperature at excitation wavelengths 1470 and 1634 Å. Primary processes are discussed in terms of variations of product yield as a function of conversion and in the presence of additives such as NO, C2D4, and H2. The relative yields of decomposition are determined at both wavelengths. The main primary process is cyclo-C3H6+hv→C2H4+CH2, the yield being 67% at 1470 Å (69% at 1634 Å). The observed product yield responsible for methylene is much less than that for ethylene. However, the yields become equal in the photolysis of cyclopropane with excess hydrogen. The other primary processes are as follows in order of decreasing importance; cyclo-C3H6+hv→C2H3+CH3, 19% (18%), cyclo-C3H6+hv→C3H4+2H, 9% (7%), cyclo-C3H6+hv→C2H2+CH3+H, 3% (4%), cyclo-C3H6+hv→C2H2+CH4, 1% (1%).