Cellotetraose and Cellopentaose

Dickey and Wolfrom separated a cellulose acetolyzate into a polymer-homologous series of crystalline sugar acetates complete from a-D-glucose pentaacetate through a-cellohexaose eicosaacetate by the application of chromatographic procedures. 

Additional proof that only /S-n-glucopyranoside linkages are present in the isolated oligosaccharides is furnished by the molecular rotation of 

If the type of linkage is entirely uniform, a linear relation should be found 

As previously considered in the case of the oligosaccharides, the molecular rotation of cellulose is an additive function of the optical rotations contributed by the constituent basic units. When the number of intermediate basic units become infinitely large, the m value in equation 

From the evidence presented, the structural formula of native cellulose may be schematically represented as in Fig. 2, neglecting for the moment the concepts of cross linking, and the fact that by common usage of the term, a cellulosic fiber material containing no detectable, or many, end groups is still called cellulose. 

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The n.m.r. spectra of peracetylated a-cellotriose, a-cellotetraose, and a-cellopentaose have been reported." ... 

Cellulose is a carbohydrate, the structure of which may be deduced as follows. The molecular formula of cellulose is (CgHioOs), 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 polyanhydro-glucose. 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-j5-D-glucopyranosyl-D-glucopyranose (III). Finally, very careful acetolysis of cellulose produces a cellotriose, a cellotetraose and a cellopentaose and in each of these all the 1,4-links have been shown to be j8-links (from calculations of the optical rotations). Thus it follows that all the 1,4-links in cellulose are j5-links cellulose may therefore be represented by structure (IV). 

Figure 7. Analysis of normal and reduced members of the cellulose oligosaccharide series by charcoal chromatography. Components from left to right Glucose (G1) reduced cellobiose (G2H borohydride reduction) cellobiose (G2) reduced cellotriose (G3H) cellotriose (G3) reduced cellotetraose (G4H) cellotetraose (G4), and reduced cellopentaose (G5H)...

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