FREE RADICALS BY MASS SPECTROMETRY: XVI. Hg-PHOTOSENSITIZED DECOMPOSITIONS OF BIACETYL, ACETYLACETONE, AND ACETONYLACETONE

Abstract

The Hg(³P₁)-photosensitized decomposition of biacetyl proceeds by a central bond fission. Of the resulting acetyl radicals, at least 27% survive the primary act long enough to react with other radicals, or with a second excited Hg atom. Under conditions of high illumination, there is evidence that Hg(³S₁) atoms produced by stepwise excitation also play a part in the reaction by forming excited biacetyl molecules with a lifetime of the order of 1 millisecond. The photosensitized decompositions of acetylacetone and acetonylacetone were examined qualitatively. The former dissociates mainly into an acetyl and an acetonyl radical, and the latter mainly if not exclusively to form CH₃CO and C₂H₄COCH₃ radicals. Further reactions of these radicals, and a possible structure for the C₂H₄COCH₃ radical, are also discussed.