Cellulose periodate-oxidized, structure

There are several methods to modify the chemical structure of cellulose hy oxidation. Periodate oxidation of cellulose suspended in water and N2O4 oxidation of cellulose suspended in chloroform are well-known conventional methods to convert cellulose to dialdehyde cellulose and C6-carhoxy cellulose, respectively. Generally, however, some side reactions including depolymerization are inevitable during these oxidations, and it is difficult, therefore, to achieve completely regioselective oxidation. 

P-Mannan is water-insoluble and solubilizing it requires very strong alkali, cuprammonium or derivatization. X-ray and electron diffraction show that mannan has a ribbon-like conformation, similar to cellulose, with the 2-OH axial instead of equatorial. In seeds (palm, coffee, caraway) a few (<5%) of a-Gal groups are attached to the hydroxymethyl and in seaweeds a small percentage (<5) of Glc residues may occur in the chain. A pure P(l-4) mannan has been extracted from cell walls of the siphonous green alga Codium latum as the methylol mannan with paraformaldehyde dimethylsulphoxide. It was purified by size exclusion chromatography in dimethyl sulphoxide and recovered by the addition of water or methanol and could be re-dissolved in hot dimethyl sulphoxide. Infra-red and n.m.r. spectroscopy and periodate oxidation confirmed the unbranched P(l-4) structure [185]. 

Complex side-reactions, including overoxidation, are likely to occur in the oxidations, and information on the mechanism of periodate oxidation and the periodate-oxidation products of starch, cellulose, xylan, and other polysaccharides have been discussed. Thus, the limit of periodate oxidation is not always that expected, and the formation of interresidue hemiacetal structures during the oxidation can cause an early halt. - It is not until these structures have been reduced that oxidation can proceed once more. Other oxidants, such as dichromate-sulfuric acid, dichromate-oxalic acid, and sodium hypochlorite (which cause more extensive reactions), have been investigated with respect to cellulose and periodate-oxidized cellulose. Further oxidation of 2,3-dialdehydocel-lulose with halogen peroxy acids gives 2,3-dicarboxycellulose. ... 

Maltotetraose has been isolated as an amorphous solid, [ ] +165.5° (water), from corn sirup concentrate by a combination of charcoal-column elution and cellulose-column chromatography. The structure was determined by periodate oxidation and by hydrolysis with i -amylase 144)-... 

In 1945, Ken, who was now Lecturer at Bristol University, was again invited by Hirst to move with him to Manchester University, this time as Senior Lecturer in Organic Chemistry. Once more, it became necessary for Hirst to concentrate his efforts on University and Government committee work. Ken Jones, therefore, took charge of the carbohydrate-research group, and supervised the completion of the explosives work. During this interval, Ken enjoyed the able collaboration of Dr. T. G. Halsall in studies on the structures of starch, cellulose, and glycogen, and on the oxidation of carbohydrates by periodate. The close association of Ken with Professor Hirst, which continued at Manchester University until 1948, was a tremendously fruitful one over 50 joint publications resulted from their research on complex polysaccharides. 

Jackson EL, Hudson CS. Studies on the cleavage of the carbon chain of glycosides by oxidation. A new method for determining ring structures and alpha and beta configurations of glycosides. J Am Chem Soc 1937 59 994-1003. Jackson EL, Hudson CS. The structure of the products of the periodic acid oxidation of starch and cellulose. J Am Chem Soc 1938 60 989-991. 

Periodate ion (see Chapter VI) is a useful oxidant in the determination of polysaccharide structures since it indicates the number of a-glycol groups present. (See also p. 648.) Thus, 1—>4 linked glycans such as starch or cellulose have free hydroxyl groups at C-2 and C-3 of each sugar unit and are... 

It is well known that polyamides and polyether chains are cleaved in hydrolytic conditions. Polymers containing OH in the a position, such as cellulose or poly(vinyl alcohol), can be cleaved by an oxidizer such as periodic acid or lead tetraacetate (reaction 25). The cleavage is very specific, as explained by its mechanism in Scheme 30, and this reaction allows the determination of head to head structures in PVA. 

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