The photolysis of gaseous aldehydes. I. The production of Ethane and Hydrogen in the Photolysis of Acetaldehyde

Abstract

The rate of production of ethane in acetaldehyde photolysis has been calculated from iodine-methyl trapping experiments, and compared with the experimental values over the temperature range 120-360 °C. The ratio of observed to calculated ethane rises from 0.5 at 120 °C to 2 at 350 °C, whilst the ratio of observed hydrogen to observed ethane rises from 0.25 at 120 °C to 1 at about 300 °C. The activation energy using the methyl radical concentration was calculated to be 7.4 kcal mole^-1 for the reaction CH₃ +CH₃CHO+CH,+CH₃CO. It was concluded that formyl radical recombination occurred in a higher temperature region (up to about 300 °C) than acetyl radical recombination (up to about 200 °C), for the experimental conditions used. It was also found that in the temperature region above about 250 °C a significant hydrogen atom chain initiation occurred.