Photolysis of cyclopentanone

Abstract

The effect of wavelength and pressure on the distribution of products has been studied in the photolysis of cyclopentanone and cyclopentanone-2,2,5,5-d4. At low pressures, C2D4 and C2H4 are formed in addition to the expected high pressure product C2H2D2, confirming the intermediate formation of excited cyclobutane. The high pressure ratio of cyclobutane to ethylene is attributed to alternate reactions of the tetramethylene diradical which have equal energy sensitivity, and some evidence is presented for a further mechanism of ethylene formation at short wavelengths. Evidence is also presented for the formation of cyclobutane and ethylene following thermal re-excitation of the precursor of 4-pentenal.