The reactivity of O-acylglycosyl halides. Part IX. Reaction between alkali-metal halides and tetra-O-acetylglycosyl bromides

Abstract

The mechanism of hydrolysis and halogen-exchange reactions of a series of acetylglycosyl bromides in acetone has been investigated. Under the non-solvolytic conditions used, only acetylmannosyl bromide hydrolyses at a measurable rate when alkali-metal halides are absent. In the presence of lithium bromide, the 1,2-cis-glycosyl halides hydrolyse at rates which are identical with the rates of bromide exchange for these halides. Similar results were obtained with sodium iodide.

From the kinetics and the effects of temperature when alkali-metal halide is present bimolecular halogen exchange appears to be the rate-determining step which occurs before rapid hydrolysis.