Some Complicating Factors in the Photolysis of Acetone

Abstract

The photolysis of acetone has been investigated a t room temperature using low pressures and high intensities. In addition an investigation was made of the photolysis of azomethane-acetone mistures. The r e~u l t s~i n d i c a t e that the curvature a t low temperatures of Arrhcnius plots of ~~~, /~~~~~[~c e t o n e ] is due to two causes ( a ) a reaction between methyl radicals and adsorbed acetone and (b) t o the occurrence of the disproportionation reaction CHa+CHsCO+ CHd+CH2CO. Confirmatory evidence for wall effects was obtained from experiments a t low pressures and higher temperatures.

Photolysis of Diethyl Ketone at Low Pressures: The Pressure Dependency of the Combination of Ethyl Radicals

“…Both studies were made on the photolysis of acetone a t low pressures whereby it is possible to compare the rate of ethane formation by combination t o the rate of methane formed by the abstraction mechanism, The magnitude of the pressure effects on the relative rates of methane and ethane production can be explained for the most part by such a mechanism, but the lower pressure experiments of Dodd and Steacie indicate other anomalies which are strongly surface dependent. These latter effects have been verified by similar low pressure experiments of -4usloos and Steacie (1). This paper reports on a similar investigation of the pressure dependency of the combination of ethyl radicals formed in the photolysis of diethyl ketone.…”

“…I lysis of acetone given by Ausloos and Steacie (1). Since the influence of a I heterogeneous reaction should not be appreciably different for the two ketones, the minima a t lower pressures in the case of diethyl lietone could well indicate a much smaller third body effect.…”

The Photolysis of Methyl Ethyl Ketone

“…In reaction [6] there are three primary hydrogens in the ethyl radical which may be abstracted in the disproportionation reaction, while in reaction [4] there are six. On this basis [4] may be expected to be of the order of twice as fast as [6]. Similarly one would expect [16] to be faster than [18] in the ratio 6/3, and [22] to be faster than [20] in the ratio 12/4.…”

“…Recent work on the photolysis of diethyl ketone (7,9,10) gives accurate informatioil on the relative rates of reactions [4] and [5], i.e. k4/k5 = 0.125.…”

The reactions of CF3 and CD3 radicals with boron trimethyl

“…Acd, 5 C D 3 C 0 + CD3 Ausloos and Steacie [13] propose that the acetyl radical can lead to methane through reaction (8), and also by a heterogeneous reaction between CH3 radicals and absorbed acetone at low temperatures.…”