Photolysis of Cyclobutane at Photon Energies Below and Above the Ionization Energy

Abstract

The photolysis of cyclo‐C₄H₈ and of cyclo‐C₄H₈—cyclo‐C₄D₈ mixtures has been investigated at 1470 and 1236 Å in the absence and presence of NO. In addition, a series of experiments carried out in which H₂S was used as a free‐radical interceptor in the photolysis of cyclo‐C₄D₈ at 1236 Å. Approximately 90% of the observed products can be accounted for by the primary process: C₄H₈+hv→2C₂H₄. The extent to which the internally excited ethylene formed in this process will decompose further increases with diminishing pressure and wavelength. The photolysis of cyclobutane has been investigated at energies above the ionization energy (I.E.=10.3 eV), using the argon resonance lines at 11.54 and 11.72 eV. It is shown that when NO is added to the system, cis‐2‐butene, trans‐2‐butene, and 1‐butene are major products. These butenes are, however, not produced when NO (I.E.=9.25 eV) is replaced by O₂ (I.E.=12.1 eV) and are only formed in trace amounts when no additives are present. It is suggested that the parent ion acquires the olefinic structure and undergoes charge exchange with NO.