Radical Reactions of Carbohydrates

Volume II: Radical Reactions in Carbohydrate Synthesis

Chapter 14: Nitro Compounds

Chapter 14 is in a portable document file (pdf) and can be viewed by clicking the blue, Chapter 14 button below. The drawing underneath the button pictures the formation and reaction of an oxygen-centered carbohydrate radical produced from an O-nitro carbohydrate. Beside the drawing is a description of the reaction. Below the drawing and its description is a summary of Chapter 14.

Chapter 14: Nitro Compounds

This drawing shows the reactions of an O-nitro compound to produce an alkoxy radical.

Drawing Description

Alkoxy radicals fragment readily to produce carbonyl groups and carbon-centered radicals. In the drawing shown on the left, which is Scheme 12 in Chapter 14, the alkoxy radical that undergoes fragmentation is generated from an O-nitro carbohydrate.

Summary of Chapter 14

The type of radical produced by reaction of a nitro group in a carbohydrate depends upon whether this group is bonded to a carbon or an oxygen atom. A nitro group bonded to an oxygen atom invariably fragments to produce an alkoxy radical, but a nitro group attached to a carbon atom either fragments to generate a carbon-centered radical, expels an oxygen-centered radical to form a nitroso compound, or abstracts a hydrogen atom.

The alkoxy radicals produced from O-nitro carbohydrates rapidly abstract hydrogen atoms either internally or from molecules present in solution. Competing with or, in some instances, superseding hydrogen-atom abstraction is carbon–carbon bond cleavage to give a carbonyl group and a carbon-centered radical.

The carbon-centered radicals derived from reaction of C-nitro carbohydrates form most readily if the radical being produced is tertiary. These radicals undergo typical replacement, addition, and cyclization reactions. Primary radicals are much less likely to form from C-nitro carbohydrates; instead, these carbohydrate derivatives usually produce nitroso compounds.