Vacuum Ultraviolet Photochemistry. Vi. Photolysis of Cyclopropane With the Xenon Resonance Lines

Abstract

The photolysis of cyclopropane has been carried out at 1470 A, at room temperature. The relative yields of products as well as isotopic analyses of hydrogen, methane, and ethylene resulting from the photolysis of equimolar mixtures of cyclopropane and cyclopropane-de indicate the following primary processes in order of decreasing importance: c-C3Hs -* CH2 + C2H4; c-C3H6 -* H2 + C3H4; c-C3H6 -* + C3H3. Atomic hydrogen probably forms molecular hydrogen by wall recombination. It is suggested that methane and ethane are formed from the methyl radical produced in the reaction: CH2 + c-C3H6 -*• c-C3HsCH3* -> CH3 + C3Ht. The mechanisms of formation of other products are discussed briefly.

Vacuum ultraviolet excited state dynamics of the smallest ring, cyclopropane. II. Time-resolved photoelectron spectroscopy and ab initio dynamics

“…Previous gas phase studies have shown that photolysis of cyclopropane occurs in vacuum-ultraviolet (VUV) for excitation energies ranging from 7.6 to 10.0 eV. [15][16][17][18] These reports highlight that branching between numerous reaction pathways can result, including the dissociation of cyclopropane, to yield ethylene and the methylene radical, c-C 3 H 6 hν − − → C 2 H 4 + CH 2 .…”

Gas-Phase Photolysis and Radiolysis of Cyclopropane

“…According to the results given in Table II the yield of D2 which represents the maximum yield of molecular hydrogen is quite small (D 2 /CtD4,.....,,0.03) at 1470 A. Because D2 can also be formed by secondary decomposition of internally excited fragments or rearrangement species such as CD3CDCD2, it may be concluded that Process (2) proposed by Currie et al 4 is of very minor importance at 1470 A. At 1236 A the relative yield of D2 is higher, but so is the internal energy of the species formed in the primary processes.…”

“…This study is concerned mainly with results obtained in the gas-phase photolysis of cyclopropane at wavelengths below and above its ionization energy (10.06 eV).a The photolysis of pure cyclopropane at 14701 (8.4 eV) has been investigated by Currie et al 4 but no information concerning the photolysis of this compound at shorter wavelengths has appeared in the literature.…”

“…Paaaa) . (29) paoo 15 3 pat 5 paaa (4) Determine the discontinuity in the second temperature derivative of the pressure at the critical point. With pat and Pooa known, Eqs.…”

Radiation and Photochemistry

“…The primary processes proposed by Gossauer are essentially the same as those reported to occur at shorter wavelengths by Doepker & Ausloos (46) . In the photolysis of cyclobutane (82) and cyclopropane (131), the detachment of an Hz molecule in a primary process occurs with a much lower quantum yield than in the photolysis of cyclohexane or of n-alkanes. In the case of cyclobu tane, the major dissociative process occurring at photon energies above and below the ionization energy is as follows :…”