Cellobiose acetolysis

The preparation of a-cellobiose octaacetate by the acetolysis of cellulose was discovered by Franchimont, and the process has been studied carefully by a number of other investi-... 

The highly polymerised compound cellulose is broken down into its octa-acetyl disaccharide cellobiose by acetolysis (Franchimont, Skraup, Ost). The bioses belong to the important group of glucosides. 

An interesting observation, not commented on in mechanistic arguments, is that the acetolysis of methyl 2,3,4,6-tetra-0-acetyl-j8-D-glucopyranoside is slower than that of methyl 2,3,4-tri-0-acetyl-6-deoxy-jS-D-glucopyranoside. A similar result has been observed in the cellobiose series. ... 

Cellulose is a carbohydrate, the structure of which may be deduced as follows. The molecular formula of cellulose is (C6HioOs)n, where n is a few thousand (see later). Hydrolysis of cellulose by boiling with concentrated hydrochloric acid yields D-glucose (II) in 95-96% yield. Thus cellulose is a polyanhydroglucose. When cellulose is subjected to acetolysis (i.e., simultaneous acetylation and hydrolysis) by treatment with a mixture of acetic anhydride and concentrated sulphuric acid, cellobiose octa-acetate is formed. Thus the structure of cellulose is based on the cellobiose unit. Cellobiose is known to be the disaccharide, 4-0-j3-D-glucopyranosyl-D-glucopyranose (III). Finally, very careful acetolysis of cellulose produces a cellotriose, a ceUotetraose and a cellopentaose and in each of these all the 1,4-links have been shown to be j3-links (from calculations of the... 

Cellulose is present in the pure state in the hairs of the cottonseed. Complete acid hydrolysis of cellulose by strong, concentrated mineral acids gives D-glucopyranose in quantitative amounts. Careful partial hydrolysis in the presence of acetic anhydride and sulphuric acid (acetolysis) gives molecules of cellobiose (4-D-glucopyranose-j3-D-glucopyranoside) and trisaccharides which can be hydrolysed by the enzyme emulsin. Hence, it... 

On hydrolysis, cellulose yields glucose exclusively, and w hen acetylated and hydrolysed simultaneously (acetolysis) it yields 50 per cent, of cellobiose (4-)S-gluco8ido-glucose), which indicates that cellulose is a chain of -glucosidic units. 

Much supplementary evidence has accrued to support this structure. Acetolysis, or partial hydrolysis with subsequent acetylation, yields the octaacetate of the disaccharide cellobiose, a diglucosaccharide known to be / -D-(i - 4)-linked, and an homologous series of higher saccharides, all )8-d-(i - 4)-linked. No evidence of chain branching is found. Cellulose reacts with one mole of periodate per component D-glucose unit, with scission of the C-2 to C-3 bond. No periodate-resistant residues are found, which is indicative of the absence of branching. 

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