Oxidation of glucose

The oxidation of glucose, a cheap and renewable starting material, represents a challenging target for chemical intermediates, mainly when clean technologies can be apphed. 

If the control volume is a piece of tissue, the reaction above may take place in an aqueous solution (aq). Consider an aqueous solution of 0.01 mol/L glucose the partial pressure of carbon dioxide and oxygen are 0.07 and 0.21 atm, respectively. From Table B8, we obtain the enthalpy of formations for the components of the reaction above at the standard state (298 K and 1 atm) 

From Table B8, we see that the difference in enthalpy between solid and dissolved glucose is 11 kJ/mol, while the differences in enthalpy of formation for gas and dissolved matter is 20 kJ/mol for carbon dioxide and 10 kJ/mol for oxygen. For all the components in aqueous solution, we find from Table B9. 

the transfer of gaseous components to aqueous solutions is small 60/2810 0.02 or 2%. The reaction enthalpy at 310 K can be estimated from 

This value is the same as the one in Table B9, and shows that the temperature correction for the heat of reaction is less than 0.2% and is often negligible. The energy expenditure (/ ) at a glucose consumption of 390 g/day is 

As for hydrogenation, heterogeneous catalytic oxidation of carbohydrates was essentially performed in the presence of carbon-supported metal catalysts, namely Pt, Pd or Bi-doped Pd.[57] Oxidation of glucose into gluconic acid, the worldwide production of which is around 60000 tons year 1,[52] is used in the food and pharmaceutical industry, and is produced today by enzymatic oxidation of D-glucose with a selectivity in gluconic acid close to 100%. 

Ti-containing zeolites have recently appeared as selective oxidation catalysts, in particular the TS-1 catalyst.[58] TS-1 has a MFI structure with small pore dimensions so that its used is not suitable for the oxidation of carbohydrates. Several attempts have been made to incorporate Ti in MCM-41 materials in order to perform oxidation of carbohydrates.[59,60] 

In the a approach by Mombarg et a/.,[59] oxidation of disaccharides, such as trehalose and sucrose (25 mmol), was performed in 25 ml of water at 70 °C, with 100 mg of Ti-MCM-41 (7.2 pmol of Ti) and 25 g of 35 wt% H2O2, at pH = 4. After 20 h of reaction, a deep oxidation is observed leading to C1-C4 mono- and dicarboxylic acids, formic acid, glycolic acid, tartronic acid and tartaric acid. The absence of selectivity is then a major drawback compared with other oxidation processes, but another drawback was identified with Ti leaching from the molecular sieve framework. 

The situation was not so simple since similar results, conversion and selectivity, were obtained when comparing Ti-Y with the TiC 2-P25 catalyst from Degussa. Again, Ti-free materials were also found to be active. ZSM-5, Mordenite and L zeolites were shown to have nearly comparable glucose conversions (around 30%) and gluconic acid selectivity (around 20%), whereas Y and MCM-41 zeolites were found to be less active, but more selective, particularly in the case of Y (27%). Although the activity of the Ti-free Y catalyst is lower than that of the Ti-Y catalyst, a similar selectivity in gluconic acid is obtained for both catalytic materials, but the selectivity in other acids is less over the Ti-Y catalyst. 

To conclude this short survey, it appears that microporous and mesoporous materials performant catalysts may be suitable for food and nonfood transformation of carbohydrates. Their acidic or basic, as well as their hydrophilic or hydrophobic, properties can be easily modified to take into account the different parameters required for a given reaction. Significant gains in activity and product selectivity are often obtained in the reactions reported except in the oxidation of glucose. 

The initial product is gluconic acid lactone. Perlmutter-Hayman and Persky showed that at pH 1.25 and 0 °C, the rate coefficient for attack of hypobromous acid on glucose is 2.04x10 l.mole sec (the corresponding rate coefficient for attack by molecular bromine is 7 times greater). The rate coefficients both for attack by HBrO and Br2 increase with increase of pH beyond 3. This increase is attributed to the much greater reactivity of the glucose anion. 

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Colourless crystals m.p. I25°C, soluble in water and alcohol. In aqueous solution forms equilibrium with its lactones. Gluconic acid is made by the oxidation of glucose by halogens, by electrolysis, by various moulds or by bacteria of the Acetobacter groups. 

By saccharic acid is usually meant D-gluco-saccharic acid, m.p. 125-126°C, obtained by the oxidation of glucose or starch. This exists in water solution in equilibrium with its two y lactones, both of which can be obtained crystalline, though the acid itself does not crystallize readily. 

Glucose oxidase, which catalyzes the oxidation of glucose to gluconic acid. 

The net stoichiometric equation for the oxidation of glucose, using the glycerol phosphate shuttle, is... 

Coupled reactions are common in human metabolism. Spontaneous processes, such as the oxidation of glucose,... 

What happens to the energy from the oxidation of glucose A study of the breakdown of glucose in the absence of oxygen shows that about 20 kcal are liberated per mole of glucose consumed ... 

Several biosensors are commercially available. One of the most useful is the glucose sensor. The standard sensor determines glucose concentration based on the glucose oxidase enzyme. The chemical reaction for oxidation of glucose is ... 

We could not live without combustion reactions the oxidation of glucose powers our bodies, and the burning of fossil fuels (coal, petroleum, and natural gas) powers our homes and vehicles. Because fossil fuels reserves are limited, alternatives are being sought (Box 6.2), but even these new fuels will be burned. Consequently, the study of combustion is critically important for our survival. 

This important relation tells us that, if we know the change in Gibbs free energy of a process taking place at constant temperature and pressure, then we immediately know how much nonexpansion work it can do. For instance, for the oxidation of glucose,... 

Wenkin, M., Touillaux, R., Ruiz, P., Delmon, B., and Devillers, M. (1996) Influence of metallic precursors on the properties of carbon-supported bismuth-promoted palladium catalysts for the selective oxidation of glucose to gluconic acid. Appl. Catal., A, 148, 181-199. 

Oxidation of Glucose Yields Up to 38 Mol of ATP Under Aerobic Conditions But Only 2 Mol When O2 Is Absent... 

The pentose phosphate pathway, present in the cytosol, can account for the complete oxidation of glucose, producing NADPH and COj but not ATP. 

Fats such as palmitic acid are metabolized through pathways similar to the ones for the oxidation of glucose. The complete oxidation of palmitic acid has a standard free energy change of-9790 kJ/mol and produces 130 ATP molecules per molecule of palmitic acid consumed. You should be able to verily that this metabolic process has about the same efficiency as the oxidation of glucose. 

A second principle used widely for glucose analysis, is that of the oxidation of glucose enzymatically, mediated by the action of glucose oxidase with the formation of gluconic acid and hydrogen peroxide (22). In this procedure it is the hydrogen peroxide which is usually assayed for determination of glucose. This method suffers from the action of inhibitors which occur, particularly with patients in a diabetic coma and these need to be removed. 

Enzyme sensors are based primarily on the immobilization of an enzyme onto an electrode, either a metallic electrode used in amperometry (e.g., detection of the enzyme-catalyzed oxidation of glucose) or an ISE employed in potentiometry (e.g., detection of the enzyme-catalyzed liberation of hydronium or ammonium ions). The first potentiometric enzyme electrode, which appeared in 1969 due to Guilbault and Montalvo [140], was a probe for urea with immobilized urease on a glass electrode. Hill and co-workers [141] described in 1986 the second-generation biosensor using ferrocene as a mediator. This device was later marketed as the glucose pen . The development of enzyme-based sensors for the detection of glucose in blood represents a major area of biosensor research. 

A bi-enzymatic system (glucose oxidase -I- HRP) was also used to catalyze the synthesis of phenolic polymers. The polymerization of phenol, albeit in moderate yield, was accomplished in the presence of glucose avoiding the addition of hydrogen peroxide (Scheme 2 ), which was formed in situ by the oxidation of glucose catalyzed by glucose oxidase. 

C NMR spectra were recorded in water on a Bruker 300 MHz without adjusting the pH. The assignment of peaks in the oxidation of glucose was made by comparison with original samples. 

S (2)-hydroxy-3-butenenitrile from acrolein and HCN trans hydrocyanation using, for instance, acetone cyanohydrin Hydrolysis of nitriles to amides, e.g. acrylonitrile to acrylamide Isomerization of glucose to fructose Esterifications and transesterifications Interesterify positions 1 and 3 of natural glycerides Oxidation of glucose to gluconic acid, glycolic acid to glyoxalic acid... 

Figure 12.6 The immobilized glucose oxidase/lactoperoxidase system radioiodinates proteins through the intermediate formation of hydrogen peroxide from the oxidation of glucose. H2O2 then reacts with iodide anions to form reactive iodine (I2). This efficiently drives the formation of the highly reactive H2OI+ species that is capable of iodinating tyrosine or histidine residues (see Figure 12.2).

Since the first report on the ferrocene mediated oxidation of glucose by GOx [69], extensive solution-phase studies have been undertaken in an attempt to elucidate the factors controlling the mediator-enzyme interaction. Although the use of solution-phase mediators is not compatible with a membraneless biocatalytic fuel cell, such studies can help elucidate the relationship between enzyme structure, mediator size, structure and mobility, and mediation thermodynamics and kinetics. For example, comprehensive studies on ferrocene and its derivatives [70] and polypy-ridyl complexes of ruthenium and osmium [71, 72] as mediators of GOx have been undertaken. Ferrocenes have come to the fore as mediators to GOx, surpassing many others, because of factors such as their mediation efficiency, stability in the reduced form, pH independent redox potentials, ease of synthesis, and substitutional versatility. Ferrocenes are also of sufficiently small size to diffuse easily to the active site of GOx. However, solution phase mediation can only be used if the future biocatalytic fuel cell... 

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