Reactions of methyl radicals with acetaldehyde and acetaldehyde‐<i>d</i>₁. I. relative rates of atom abstraction reactions at 785°K

Abstract

Abstract The role of ethenoxy radicals in the pyrolysis of CH 3 CDO was studied by mass spectrometric analysis of the isotopic composition of the methane, ethane, and recovered aldehyde. Experimental evidence was obtained for the formation of ethenoxy radicals and for their reaction with acetaldehyde. Mixtures of CH 3 CHO and CH 3 CDO were pyrolyzed in order to minimize H‐D scrambling in the methyl group of the aldehyde. A kinetic treatment of the methyl radical reactions equation image and equation image furnished the rate constant ratios ( k 2a + k 2b )/ k 1a = 2.7 and k 1b / k 1a = 0.62 at 785°K. It is concluded that at the usual temperatures of CH 3 CHO pyrolysis the rate of alkyl hydrogen capture is comparable to that of formyl hydrogen abstraction. The results and conclusions are discussed and compared with previous work.