A-Cellobiose, octaacetate

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-... 

Interproton distances of 0-ceIIobiose (see Ref. 49) error 0.01 A. Interproton distances of 1,6-anhydro- -D-glucopyranose (see Ref. 49) error 0.01 A. Interproton distances of -cellobiose octaacetate (see Ref. 49) error 0.05 A. Interproton distances of 2,3,4-tri-0-acetyl-l,6-anhydro- -D-glucopyranose (see Ref. 49) error 0.05 A. Error calculations based on the errors of the measured quantities in Eqs. 18 and 21. Interproton distances calculated from the relaxation parameters of the methylene protons. 

Cellobiose Octaacetate and Glucose Pentaacetate. Eastman White Label materials were purified by recrystallization from a methylene chloride-methanol mixture. 

Glucose pentaacetate and cellobiose octaacetate also yielded a fraction which was insoluble in methylene chloride and which appeared polymeric and amorphous. 

Comparative investigations with related monomeric compounds, glucose pentaacetate, and cellobiose octaacetate indicate that, on a qualitative basis, these materials undergo photolytic changes in a manner similar to cellulose triacetate. These materials may serve as model compounds for future quantitative investigations of cellulose triacetate. 

C,ZH °, 1 mw 34 2.30. It seems that a-isomer was never isolated. The /3-cellobiose, col microscopic crysts(from dil ale), contains from 0.25 Jo 0.5 mole HzO mp ca 225° with decompn, ta] ° 4.34.8°(in 6% aq soln). Can be prepd by treating dry a-cellulose octaacetate with absol methanol in which some Na is dissolved(Ref 2). 

FIGURE 3.16 The effect of a tiny ferromagnetic particle on the proton resonance spectrum of cellobiose octaacetate. The top spectra are run with the particles present the bottom curves are the spectra with the particle removed. 

The synthesis of cellobiose octaacetate by the reaction of the sodium derivative of 1,2,3,6-tetraacetyl-D-glucopyranose with 2,3,4,6-tetraacetyl-a-D-glucopyranosyl bromide has recently been reported. Deacetylation resulted in the formation of cellobiose. 

Another way to learn of the likely molecular shapes for cellulose depends on extrapolation of the shapes that are found in crystal structures of molecules such as cellobiose (Chu and Jeffrey 1968), a-cellobiose complexed with Nal and HjO (Peralta-Inga et al. 2002), cellobiose octaacetate (Leung et al. 1976) and related compounds (French and Johnson 2004a). Similar, although less accurate. 

Cellobiose was prepared first by Skraup and Konig by the saponification of the octaacetate with alcoholic potassium hydroxide, and the method was improved by Pringsheim and Merkatz.3 Aqueous barium hydroxide also has been employed for the purpose, and methyl alcoholic ammonia has been used extensively for the hydrolysis of carbohydrate acetates. The method of catalytic hydrolysis with a small quantity of sodium methylate was introduced by Zemplen,i who considered the action to be due to the addition of the reagent to the ester-carbonyl groups of the sugar acetate and the decomposition of the addition compound by reaction with alcohol. The present procedure, reported by Zemplen, Gerecs, and Hadacsy, is a considerable improvement over the original method (see Note 2). 

A remarkable inertness towards acylation is shown by the secondary hydroxyl group on C-3 in maltose, lactose, and their methyl j8-glycosides. Benzoylation of maltose with 10 molar equivalents of the acid chloride in pyridine gave122 the octabenzoate and the l,2,6,2, 3, 4, 6 -hepta-0-benzoyl derivative in the ratio of 5 6, and treatment of /3-maltose monohydrate with 8.8 molar equivalents of acetyl chloride in pyridine-toluene at 0° gave123 the 1,2,6,2, 3, 4, 6 -heptaacetate and the octaacetate in the ratio of 27 10. Under similar conditions of benzoylation, cellobiose was converted into its oc-... 

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