Direct and triplet-benzene-sensitized photolysis of perfluorocyclobutanone at low pressures

Abstract

Publication costs assisted by the Office of Naval Research Perfluorocyclobutanone (PFCB) has been produced in its triplet state ( ) by the triplet benzene (3Bxu, 84.5 kcal/mol) sensitization method, and the state decomposes mainly to c-CgFe and CO. Investigation of the direct photolysis of PFCB at low pressure (<5 Torr) indicates that at low excitation energies, Sx-' '**-* intersystem crossing predominates and at high energies, Sx -*»'-*• So internal conversion predominates. The internally converted PFCB (So*) decomposes unimolecularly to C2F4 and CF2CO, and the latter product further decomposes to CF2 and CO. The total product quantum yield of the "primary" processes is unity at low pressure. Our new mechanism is similar to the mechanism proposed earlier for cyclobutanone photodecomposition but is not compatible with the singlet mechanism proposed by Phillips based on the photodecomposition study carried out at higher pressures.

Photolysis of formaldehyde-butene mixtures at low pressures. Quantum yield of radical decomposition process in formaldehyde

“…A similar experimental procedure gave a satisfactory quantum yield measurement in the photolysis of perfluorocyclobutanone, and the check of the present procedure, gave a value of 0.98 for the photodecomposition yield of cyclobutanone which is known to be l.O. 16 A H2CO/butene ratio of 1/10 was used in all experiments, and a pressure range of 0.055-1.10 Torr was used. Due to the low light intensities, photolysis times were long (15-20 h).…”