An elementary reaction is one that has no intermediates. Every reaction that forms an intermediate actually is a combination of two or more elementary reactions. Where radicals are concerned, an elementary reaction either creates a radical from a nonradical, transforms one radical into another, or causes a radical to disappear.1,2
For chain reactions the propagation phase always contains at least two elementary reactions (Scheme 1). Nonchain reactions are similar in that they also contain at least two elementary reactions (Scheme 2). The elementary reactions upon which the free-radical chemistry of carbohydrates is based are listed in a general form in Table 1.1,2 Specific examples are given in the discussion of each reaction that takes place in this chapter. In describing these reactions the term “carbohydrate radical” (CARB·) refers to a radical centered on one of the atoms, usually carbon, in a carbohydrate.