Isotope-Containing Organic Compounds as Ion-Radical Precursors

6 ISOTOPE-CONTAINING ORGANIC COMPOUNDS AS ION-RADICAL PRECURSORS 

Isotope substitution aims to ascertain whether a bond labeled with an isotope takes part in a given reaction. One then either looks at the products, noting the label distribution, or attempts to determine the kinetic isotope effect. The latter can be detected as the change in the rate constant of the reaction by using an isotope in the place of an atom taking part in the reaction of interest. 

When applied to electron-transfer reactions, this kinetic isotope effect technique can provide information on the real reaction pathway leading to the formation of the product. Frequently, spectroscopic detection of species or identification of products is indicative of radical intermediates. The formation of the intermediates could simply be a blind step. 

Concerning the change in or for isotopic substitution, cnrrently there is not much data and the exact pattern of the phenomenon is still not known. Nevertheless, it seems useful to compare the existing data both for the consideration of isotopic effects in reactions and for information on the possible new ways of nsing electron transfer for a more effective enrichment of isotopic mixtnres with one specihc isotope form. 

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Isotope-containing organic compounds as ion radical precursors have important significance for ion radical organic chemistry. The link between the isotopic substitution at the reaction center and the change in the kinetic properties is not so obvious for one-electron transfer. In that case, the highest occupied molecular orbit (MO) of a donor loses one electron. This electron is then shuttled to the lowest unfilled MO of an acceptor. 

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