Abstraction Reactions of Methylene with Deuterated Methyl Halides

Article abstract of DOI:10.1021/j100461a022

Tritiated methylene from the 3130-Angstroem photolysis of ketene-t has been reacted with unscavenged deuterated methyl halides (CD3X with X=F, Cl, Br, I) in the gas phase.The distribution of tritium among the products indicates that the reaction of CHT with CD3X often proceeds by halogen abstraction (X=Cl, Br, I) to form CHTX and CD3.The fractional yields of the radioactive products from recombination of such radicals are too large to originate solely from ³CHT reactions, and they imply therefore that most or all of this reaction must be initiated by singlet methylene, as in the following reaction: ¹CHT + CD3X --> CHTX + CD3.No halogen abstraction is observed from ketene-t photolysis in the presence of CD3F.The tritiated ethylenes formed in these systems have been analyzed for deuterium content and show measurable quantities of C2H2DT, C2HD2T, and C2D3T.The monodeuterio compound C2H2DT cannot be formed from a direct methylene/ methyl halide reaction, but instead requires a methylene / methyl reaction such as the following : ³CH2 + CHDT --> CH2CHDT^* - H --> CH2=CDT.THe ³CH2 (and ³CHT) radicals must react very slowly with CD3X in order to survive for milliseconds without chemical reaction.