Oxidation of sugar

An efficient oxidation of glucose to gluconic acid was performed using a porous gold catalyst in a low-cost microreactor designed from Pyrex glass capillary tubing [161]. 

A reaction yield of 99% was achieved in the capillary-microreactor, whereas the conventional method yielded only 48% of gluconic acid. In the capillary microreactor, the higher surface area of the porous sponge catalyst is responsible for a high reaction yield. 

Moreover, no isomerization of glucose to fructose was observed during the reaction and total selectivity to o-gluconic acid was obtained. The low cost of fabrication, disposable nature of the capillary tube, and availability of a wide range of porous catalysts make this reactor versatile and cost effective. 

Gas-hquid-sohd oxidation of glucose was also studied as a model reaction to show the methodology for the ex-ante evaluation of different processing options (95). Possible improvements using microreactor technology are evaluated. 

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Oxahc acid was synthesi2ed for the first time ia 1776 by Scheele through the oxidation of sugar with nitric acid. Then, Wn h1er synthesi2ed it by the hydrolysis of cyanogen [460-19-5] ia 1824. 

Various substituted N-hiomo- and A/-chloroureas have also been prepared (97). These compounds are useful for synthesis of oxazoUdinones, and also hydrazine, hydrazo, and azo compounds. A/-Bromourea [51918-81 -1] is useful for selective oxidation of sugar derivatives (98). 

Although equation 9 is written as a total oxidation of sugar, this outcome is never realized. There are many iatermediate oxidation products possible. Also, the actual form of chromium produced is not as simple as that shown because of hydrolysis, polymerization, and anion penetration. Other reduciag agents are chosen to enhance the performance of the product. 

The dialdehydes, such as VI and XI, produced by periodate oxidation of sugar glycosides or polymers, very probably do not exist in the aldehydo form,212-214 but in a hydrated212 and cyclized structure.213 214... 

Yields of osones obtained by the oxidation of sugars by Fenton s reagent are low, and the osones are invariably contaminated both with starting material and with the products of further oxidation in consequence, the method has had only limited application.44... 

Fig. 2.—Oxidation of sugar derivatives by lead tetraacetate in dry acetic acid 0.00025 mole substance in 100 cc. ratio of Pb(OAc)4 to substance, 15.2/1 water less than 0.05 %.

The oxidation of sugar enamines [1465 and 1466, R2 = —CH=C (COOEt)2] with potassium permanganate and potassium metaperiodate in a 1 1 mixture of acetone and water at ambient temperature gave a-hy-droxy amides [1465 and 1466, R2 = COCOH(COOEt)2] and AMbrmyl amino sugars (1465 and 1466, R2 = CHO) 42-52% and 15-28% yields, respectively [89JCS(P1) 1923]. 

Stable oxo-Cr(V) complexes were found to be formed with D-galactose (12) and D-fructose ligands, with EPR signals detectable even after 1 month.31>50>70 it was therefore concluded that periods of weeks are necessary to convert the Cr(VI) to Cr(III) complexes having saccharides as ligands, and this poses many environmental implications. In the studies of Cr(VI) oxidation of sugars conducted by Sala et al., the existence of intermediate Cr(V) complexes has indeed been firmly established.71... 

In the food processing industry flour doughs are baked. This involves many processes such as (I) rising of dough by evolution of CO2 by yeast-catalyzed oxidation of sugar to vapor in pockets or by decomposition of baking powder,... 

The observation of currents attributable to the faradaic electrochemistry of nucleic acids was pioneered by Palecek and coworkers who studied DNA adsorbed on mercury or carbon electrodes [13]. The signals detected by Palecek were attributable to oxidation of the purines, which produced signals indicative of irreversible processes involving adsorbed bases. These reactions were used as a basis for electrochemical analysis of DNA. Kuhr and coworkers later showed that similar strategies could be developed for analysis of nucleic acids via oxidation of sugars at copper electrodes [14-16]. 

Oxidation of Sugars in Alkaline Solutions with Oxygen... 

Structurally, these acids are cunsidered to be the oxidation products of polyhydric alcohols. However, a number of them can be formed from the oxidation of sugars. The careful oxidation of glycerol will yield a syrupy liquid, glyceric acid, an example of a dihydroxymonobasic carboxylic acid. 

The oxidation of sugars and polyols by halogens180 has been extensively studied. Polyols may be oxidized to aldoses and ketoses albeit in... 

A few examples of chemicals produced by oxidation of sugars include ... 

Neyhart GA, Cheng C-C, Thorp HH (1995) Kinetics and mechanism of the oxidation of sugars and nucleotides by oxoruthenium(IV) model studies for predicting cleavage patterns in polymeric DNA and RNA. J Am Chem Soc 117 1463-1471... 

G. Fleche, Oxidation of sugars with hypohalides in preparation of carboxylates used in detergents formulation, Patent EP 0798 310 A1 (1996) Chem. Abstr., 127 (1997) 307619p. 

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