PREPARATIVE LASER PHOTOCHEMISTRY OF PERFLUOROAZOETHANE

Excimer laser irradiation of liquid perfluoroazoethane (1) is compared with regular irradiation with high pressure mercury lamps. In contrast with earlier literature reports, there is rapid E-Z isomerization and the Z isomer (2) may be isolated by vapour phase chromatography (VPC). On irradiation with peak intensities in the megawatt range there is a dramatic change in the ratio between the trapping of the perfluorethyl radical by compounds 1 and 2 to give tetrakis(pentafluoroethyl)hydrazine (3) and its secondary (random) recombination to give n-perfluorobutane (4). This is because of the extraordinarily high radical concentrations which cannot be achieved by any means other than pulsed laser excitation at present.