Isotopic labeling cross-over experiments

Reaction with letramethoxyetkylene. In a reaction that is first order with respect to each of the reacUnts, tetramethoxyethylenc (I) and tosyl azide (2) yield the imido-carbunate (3). These data, as well as cross-over experiments with isotopically labeled (I), exclude any dissociation of (1) into two molecules of dimethoxycarbcnc under the conditions applied. ... 

This little bit of cross-over was postulated to be due to a hydrido exchange reaction that also occurs during photolysis. These experiments—isotope labeling, bond dissociation energy analysis, and cross-over—highlight how physical organic chemistry can be applied to a very important organometallic reaction. 

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