VII. Summary

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Radicals often exhibit reactivity characteristic of either nucleophilic or electrophilic species. An electrophilic radical reacts more rapidly with an electron-rich center in a molecule, and a nucleophilic radical is more reactive toward an electron-deficient one.

A number of procedures exist for determining the philicity of a radical. These range from simple ones that involve assignment based on inspection of radical structure combined with a general knowledge of organic chemistry to complicated ones based on ab initio molecular orbital calculations. All procedures lead to the conclusion that nearly every carbohydrate radical is nucleophilic.

Most quantitative information about rates of reaction of carbohydrate radicals comes from extrapolation of data obtained from reaction of model radicals. Although this information is useful in understanding the philicity of carbohydrate radicals, it must be treated with caution when pyranos-1-yl radicals are under consideration. Simple radicals are unable to model the stereoelectronic effects that are critical to radical stability in pyranos-1-yl radicals and, consequently, do not always provide a good measure of their reactivity.