Action of Lead Tetraacetate on the Sugars

Abstract

This chapter discusses the action of lead tetraacetate on the sugars. Lead tetraacetate appears to have been first used as an organic oxidant in place of established reagents as the dioxides of manganese and lead. With the discovery of the cleavage of glycols by lead tetra-acetate, its applicability to the sugars got recognized with their many hydroxyl groups. Glyceritol and mannitol were among the first to be examined. They consumed oxidant smoothly in glacial acetic acid at 50°, yielding two moles of formaldehyde per mole, a measurement which was to serve as an elegant diagnostic test for terminal, 1,2-glycol groups, particularly in sensitive types of compounds. The reaction of sugar dithioacetals with lead tetra-acetate may be complicated by dehydrogenation of the thioacetal groups, in addition to normal glycol-cleavage, depending on the reaction condition. The latter reaction was found to be favored in non-ionizing solvents, but in a solvent of medium or high dielectric constant, the –thio group was cleaved from the molecule. The dibenzyl dithioacetals of a group of sugars and sugar acetates in acetic acid yielded dibenzyl disulfide, probably through formation of an intermediate thiol (RSH) and with production of an aldehydo diacetate.