Abstract
PURE, anhydrous liquid acetone in the absence of oxygen reacts with iodine after absorption of ultraviolet light. In the dark a negligible change is observed in the same time. These experiments were originally designed to detect any radicals which may be formed from the photodecomposition of ketones. It is thought1 that the radicals formed at room temperature (15°) quickly recombine by the Franck-Rabinowitsch mechanism2, but at 70° they can react with the molecules of a hydrocarbon solvent with an energy of activation of 12,000 calories. They must therefore survive between e12000/2×288 = 109 and e12000/2×343 = 108 collisions with solvent, molecules before recombination, and must have a comparatively long life. In view of the high efficiency of the recombination reaction CH3 + I = CH3I3, it was thought that illuminated iodine solutions furnishing iodine atoms in concentration comparable with that of the radicals themselves would serve as a method of detecting the presence of methyl and other radicals, by their ready reaction to form alkyl iodides. But irradiated liquid acetone gave no methyl iodide or di-acetyl which could be detected.
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IREDALE, T. Photo-enolization of Ketones. Nature 150, 579 (1942). https://doi.org/10.1038/150579a0
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DOI: https://doi.org/10.1038/150579a0
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