PHOTOLYSIS OF DIETHYL KETONE AT LOW PRESSURES: THE PRESSURE DEPENDENCY OF THE COMBINATION OF ETHYL RADICALS

Abstract

The photolysis of diethyl ketone has been investigated in the pressure range 0.01–30 mm. at 100°, 150°, 200°, and 250° with a variation in absorbed intensity of 1000-fold. Over this wide variation in experimental conditions the kinetics of the reaction show excellent agreement with the mechanism of Kutschke, Wijnen, and Steacie. Under conditions where the production of ethylene by decomposition of the pentanonyl radical was negligible (high light intensity and low ketone pressure), the ratio of the rate of ethylene formed to the rate of butane produced was determined to be 0.12 independent of the temperature. These data indicate that both the disproportionation and combination of ethyl radicals are homogeneous and pressure independent to as low as 0.01 mm. pressure. In addition it is probable that the two reactions are the result of different reaction intermediates as was postulated by Wijnen and Steacie. The abstraction reactionC₂H₅+C₂H₅COC₂H₅ → C₂H₆+C₂H₄COC₂H₅showed definite heterogeneous character at low pressures similar to the analogous reaction of methyl radicals with acetone studied by Ausloos and Steacie.