I. Introduction

Aldehydes and, to a lesser extent, ketones participate in radical reac­tions of carbohydrates by generating intermediate, oxygen-centered and carbon-centered radicals. The radical addition pic­tured in eq 1 provides an example of conversion of a carbonyl compound into an oxygen-centered radical, while that in eq 2 involves transforming an aldehyde or ketone into a carbon-centered radical. [The radicals produced in the latter reaction (eq 2) are described as samarium ketyls in recognition of their partial radical-anion character.] Other reactions that generate radicals from aldehydes and ketones are photochemical bond homolysis (eq 3) and fragmentation of α‑acyloxy ketones (eq 4). The discussion in this chapter centers on the types of com­pounds that can be pro­duced by these reactions and the mechanisms for their formation.