Cellobiose 3-octaacetate

Checked by Reynold C. Fuson, William E. Ross and William P. Campbell. 

For further purification a solution of the material in 350 cc. of chloroform is clarified if necessary and poured into 750 cc. of methyl alcohol, and the mixture is cooled to 0°. The yield of the pure acetate, m.p. 225-226°, + 42.5°, is 61-65 8- 

Pure commercial cotton or filter paper may be used. These materials ordinarily contain 7-10 per cent of moisture. 

Effective stirring and careful control of the reaction are essential for obtaining good yields. If left uncontrolled, the temperature may rise quickly above 100° with considerable decomposition. 

The crystallization is accelerated by scratching the walls of the jar or by seeding. Seed is obtained easily by pouring a small portion of the reaction mixture into a large amount of water the precipitate is separated, treated with alcohol, and dried at 40°. 

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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. 

Mass Spectrometric Analysis of Volatiles during Photolysis. Samples investigated were cellulose triacetate, cellobiose octaacetate, glucose pentaacetate, cellobiose, and glucose. 

Cellobiose Octaacetate and Glucose Pentaacetate. In both cases the major component observed at 2 to 5 minutes was CH2=C=0, with lesser amounts of CO, C02, CH3COOH, and H20. H2 was not observed. 

Cellobiose Octaacetate and Glucose Pentaacetate. The results on both compounds were similar. Samples irradiated at 253.7 and 313 mfi, both in the presence of oxygen and in vacuum, were saponified. Infrared analysis of the saponified residues showed that all samples had carbonyl absorption at 5.76 to 5.78 microns, owing to lactones, ketones,... 

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. 

It can also be prepd by saponification of jS-cellobiose octaacetate with alcoholic KOH or by the action of some bacteria on cellulose(Ref 1) Refs l)Beil 31, 380-1 2)OrgSynth 17(1937), 34 CollVol 2(1943), 122... 

Cellobiose octaacetate and 1,6-Anhydro-p-cellobiose hexaacetate are compared with respect to their glycosidic conformation [93, 94], For cellobiose octaacetate it was concluded that the conformation in solution is close to that one determined by X-ray crystal structure analysis to cp = 45° and i / = 16° (Fig. 5) whereas the 1,6-anhydro derivative is demonstrated by use of NOEs, relaxation data, and coupling constants 3JC>H to adopt torsional angles of = 25° and ]c = 45° respectively. 

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. 

Problem 35.5 Why is alkaline hydrolysis of cellobiose octaacetate (better named octa-O-acetylcellobiose) to (+)-ccllobiosc preferred over acidic hydrolysis ... 

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