The thermal decomposition of acetone vapour

Abstract

The decomposition of acetone first aroused interest as an example of a unimolecular gas reaction at a time when few suitable for kinetic investigation were known. The rate of decomposition in the earlier work was inferred from the rate of pressure increase, a method which is only reliable when certain conditions are fulfilled. Whether they are fulfilled by the acetone decomposition has been questioned from time to time. The main reaction is followed by a slow decomposition of unsaturated hydrocarbons which it produces, and the correction of the "end-point" for the subsequent pressure changes is subject to some uncertainty. Further, ketene is known to be a possible decomposition product of acetone, and the suggestion has even been made that the rate actually measured was that of the decomposition of ketene, produced almost instantaneously from acetone by the reaction CH 3 COCH 3 = CH 4 + CH 2 : CO. For these reasons the reaction has been re-investigated by an analytical method which measures directly the rate of disappearance of acetone without any assumptions about the products or about their subsequent decompositions. In addition the nature of the products has been more fully studied. It has recently been suggested that acetone decomposes by a mechanism involving long chains. One important criterion of such reactions is the influence long chains. One important criterion of such reactions is the influence of the surface and the dimensions of the vessel. Therefore in the present work these factors have been carefully re-examined.