Amylose oxidation

Amination of Amylose Oxidized with Dimethyl Sulphoxide-Acetic Anhydride, M. 

Com and rice starches have been oxidized and subsequently cyanoethylated (97). As molecular size decreases due to degradation during oxidation, the degree of cyanoethylation increases. The derivatized starch shows pseudoplastic flow in water dispersion at higher levels of cyanoethylation the flow is thixotropic. Com and rice starches have been oxidized and subsequently carboxymethylated (98). Such derivatives are superior in the production of textile sizes. Potato starch has been oxidized with neutral aqueous bromine and fully chemically (99) and physically (100) characterized. Amylose is more sensitive to bromine oxidation than amylopectin and oxidation causes a decrease in both gelatinization temperature range and gelatinization enthalpy. 

Table I shows the results of periodate oxidation and methylation applied to amylopectins from various sources. If the percentage of amylose in a whole starch is known, the length of unit chain of the amylopectin component can be calculated from the results of periodate oxidation of the whole starch (see Table II). The length of unit chain appears to depend on the botanical species, but not the variety, from which the starch wras isolated. In the case of tapioca and corn amylopectins, sub-fractionation of these by precipitation with methanol, followed by periodate oxidation, showed the sub-fractions had the same degree of branching as the original amylopectins.71 The action of periodate on whole starches and amylopectins is now so well established and accurate, that it may well completely supersede the methylation technique for pure starches, in view of its many advantages.

Starch source Amylose, % Average (a) by metky-lation length of t b) by Periodate oxidation tnit chain (c) calc, for amylopectin from (6) References... 

Periodate oxidation has also been applied to this component.7 81 108 Theoretically, this method should be more satisfactory than methylation, as formation of derivatives is not necessary. However, recent work suggests that the chain length of amylose comprises several thousands of D-glucose units rather than hundreds (see Section V, 2), and the accuracy of such... 

Malto-oligosaccharide aldonolactones react with ethylenediamine to give Ar-(2-aminoethyl)aldonamides (113-115), which have been successfully grafted onto carriers via amide linkages. The malto-oligosaccharides were produced by degradation of amylose with alpha amylase. After purification of the oligosaccharides, they were converted into the lactones by hypoiodite or electrolytic oxidation. 

Exhaustive studies on well-defined systems are rather scarce (4) nevertheless 3 systems thoroughly analyzed by independant research groups are of outstanding interest a) the quaternization of polyvinylpyridines by alkyl halogenides (20-25) b) the chlorination of polyethylene (13,26-28) c) the basic or acid hydrolysis of PMMA (29-31). On the other hand, neighbouring groups effects have been quantitatively taken into account for the kinetic analysis of periodate oxidation of amylose (32,33). 

The yield is higher in basic solution in the presence of an oxidizing agent. Iodine forms a blue complex with P-amylose in starch. A hnear array of I5 species consisting of I2 -1 - I2 units bound to the amylose hehx causes blue color formation. 

Fig. 7 Maltotetraose hybrids with various carriers resulting in different chain architectures A poly(ethylene oxide) Ba and Bb poly(acrylic acid), amylose, cellulose, and other polysaccharides Ca cyclodextrin and multifunctional acids Cb amylopectin D crosslinked poly(acryl amide) [156] - Reproduced by permission of Wiley...

Structural analysis of isolated amylose and amylopectin components has been carried out by standard methods based on methylation, periodate oxidation, and partial acid hydrolysis studies. Methylation and periodate oxidation studies established the linkage types and frequency of... 

Starch (amylose and amylopectin) hydrolysis along with ester-fication, etherification or oxidation have been previously discussed as available methods for producing starch derivatives with improved water dispersibilities and reduced retrogradation potential (, ). Since oxidative and hydrolytic reactions are simple, easily controlled chemical modifications, starch-derived polymers made by hydrolysis alone or oxidative and hydrolytic processes were developed and tested. 

Rather recently, we have studied the solid-state structure of various polymers, such as polyethylene crystallized under different conditions [17-21], poly (tetramethylene oxide) [22], polyvinyl alcohol [23], isotactic and syndiotactic polypropylene [24,25],cellulose [26-30],and amylose [31] with solid-state high-resolution X3C NMR with supplementary use of other methods, such as X-ray diffraction and IR spectroscopy. Through these studies, the high resolution solid-state X3C NMR has proved very powerful for elucidating the solid-state structure of polymers in order of molecules, that is, in terms of molecular chain conformation and dynamics, not only on the crystalline component but also on the noncrystalline components via the chemical shift and magnetic relaxation. In this chapter we will review briefly these studies, focusing particular attention on the molecular chain conformation and dynamics in the crystalline-amorphous interfacial region. 

For the oxidation of primary hydroxyl groups, three times the amount of nitrite is required when compared with nitrate, and three times as much of the toxic NO would be formed. This oxidation procedure has been applied to the glucans cellulose, amylose, and pullulan. A study of this system with cyclomaltoheptaose (/J-cyclodextrin) showed that the reaction is autocatalytic. 

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