Aqueous Solutions Of D-glucose Research Articles

Glucose Hydrogenation in a Trickle-Bed Reactor

Catalytic hydrogenation of 40% aqueous solutions of D-glucose to D-glucitol was studied in a high-pressure trickle-bed reactor. The reactions were performed on a supported nickel catalyst at temperatures ranging from 115 to 165 °C and in the pressure range 0.5 to 10 MPa. The order of the reaction with respect to hydrogen is 0.65 and apparent activation energy 23.8-48.5 kJ mol-1, the latter depending on initial molar glucose concentration and density and viscosity of the solution. The influence of external diffusion is necessary to take into account for scaling-up the process.

Kinetics of glucose hydrogenation in a trickle-bed reactor

The kinetics of the catalytic hydrogenation of aqueous solutions of d-glucose to produce sorbitol was studied in a high pressure trickle-bed reactor with cocurrent downflow mode. The hydrogenation reactions were performed on a supported nickel catalyst in the temperature range 343 to 403 K and in the pressure range 4 to 12 MPa. Reaction rates were measured on the catalyst extrudates as such or after crushing and sieving them. The kinetic data obtained from measurements of the initial reaction rates as a function of temperature, pressure and mass of catalyst were interpreted with a Langmuir-Hinshelwood rate law where the reaction between adsorbed glucose and hydrogen is the rate-determining step.

Electroosmotic Transport of Urea and d-Glucose Solutions across Progesterone Plug Membrane

Abstract Studies on hydrodynamic and electroosmotic permeation of water, aqueous solutions of d-glucose and urea in the concentration range 10−4 to 10−3 mol dm−3 across progesterone plug membrane have been carried out to characterize the electrical nature of interface. Phenomenological coefficients have been evaluated from the linear and nonlinear equations obtained. Membrane properties viz., pore radius and zeta potentials have been determined using these coefficients. The nonlinear variation of electroosmotic flow in case of aqueous solutions of urea has been explained on the basis of electrical double layer theory and the structural modifications that are likely to occur at membrane–solution interface because of solute–solvent, solvent–solvent, and membrane–permeant interactions.

Preparation of photoinitiator-bound celluloses and their reactivity

Photoinitiator-bound celluloses (Cell-AQ and Cell-BP) were prepared by reaction of epoxy-activated cellulose with, respectively, 1-aminoanthraquinone (AQNH 2) and 4-aminobenzophenone (BPNH 2) in N, N-dimethylformamide at 70°C. About 60% of the initial epoxy groups (1·90–2·10 mmol/(g cellulose)) was found to participate in the reaction under alkaline conditions. The photoinitiator-bound celluloses exhibited an activity towards photoinduced formation of hydrogen peroxide in aqueous solutions of d-glucose, and isopropyl alcohol. The amount of hydrogen peroxide formed was higher for the Cell-BP than the Cell-AQ. Moreover, the photoinitiator-bound celluloses showed an ability to initiate photografting of methyl methacrylate at 60°C in a water medium, indicating a higher percentage of grafting and a lower percentage of homopolymer compared to photoinitiator-sensitized celluloses, which were prepared by immersing a cellulose sample in acetone solutions of AQNH 2 and BPNH 2 and drying under vacuum to remove the solvent. It was found that the photoinitiator residues introduced into the cellulose substrate are capable of abstracting hydrogen atoms from the substrate.

Gel-permeation chromatography of solutions of d-glucose after irradiation by ultrasound and γ-rays

Gel-permeation chromatography on the COO − and COOH forms of Ultrahydrogel 20 of aqueous solutions of d-glucose irradiated with ultrasound and γ-rays, followed by g.l.c.-m.s. of the trimethylsilylated methoximated derivatives of the products, revealed derivatives of gluconic acid and hexulosonic acids after irradiation in the presence of air and 2-deoxy- arabino-hexonic and gluconic acid after irradiation under argon. A small proportion of products was formed with molecular weights larger than that of glucose and which contained an enolic structure.

Action of ultrasound on deoxygenated aqueous solutions of d-glucose

The action of ultrasound on deoxygenated aqueous solutions of d-glucose yielded d-gluconic acid, d- arabino-hexos-2-ulose, d- ribo-hexos-3-ulose, d- xylo-hexos-4- and -5-ulose, d- gluco-hexodialdose, 2-deoxy- d- arabino-hexonic acid, 5-deoxy- d- xylo-hexonic acid, 6-deoxy- l- threo-hexos-4,5-diulose, and 6-deoxy- d- threo-hexos-2,5-diulose. There was little cleavage of the carbon skeleton. The ratio of the deoxy compounds to the sum of the hexosuloses and the hexodialdose was smaller on sonolysis than on γ-irradiation.

Electrophoresis of Progesterone Particles Dispersed in Aqueous Solutions of d-Glucose and Urea

Abstract Electrophoretic mobilities of progesterone particles dispersed in aqueous solutions of d-glucose and urea, in the concentration range 10−3–104 mol l−1 have been measured to investigate electrical properties of the interface. Zeta potentials have been determined for this purpose. The dependence of zeta potentials on concentration has also been examined. Theory of the electrical double layer has been used to explain the results.

Interactions between hydrophilic and hydrophobic structure maker solutes. Excess enthalpies of ternary aqueous solutions of D-glucose and alcohols at 25 °C

The coefficients of the virial expansion of the excess enthalpies of ternary aqueous solutions containing D-glucose and an alcohol (ethanol,n-propanol,n-butanol andtert-butanol) were determined at 25 °C. The trend of the cross coefficients versus the self coefficients of the alcohols exhibits a maximum in accordance with the system containingtert-butanol. This behaviour is similar to that found for the interaction of the same alcohols with any other hydrophilic solute examined up to now. The results are interpreted in terms of a prevailing release of water from the structured cospheres of the alcohols.

ESR spin trap investigations on aqueous glucose solutions irradiated by ultrasound and gamma-rays

Applying 5,5-dimethylpyrroline- N-oxide (DMPO) as the spin trap, the radical adducts produced by ultrasound and γ-irradiation of water and aqueous solutions of d-glucose are compared. In the ESR-spectra obtained for sonolysis and radiolysis of water, H- and OH-adducts are present. In glucose solutions for both types of irradiation the H-adduct is also detected. However, OH-adduct is completely lacking and there is no evidence for the formation of adducts originating from glucosyl radicals. To explain these experimental observations the following mechanism is proposed: the OH- and H-radicals produced by sonolysis or radiolysis in water abstract carbon bond hydrogens from glucose generating glucosyl radicals. This explains the lack of OH-adducts. The glucosyl radicals stabilise by H-transfer to the spin trap. This explains the presence of H-adducts and the lack of glucosyl-adducts. The splitting constants of three additional radical adducts, which are present in minor concentrations as well in water as in glucose solutions, were evaluated. They are supposed to be spin adducts resulting from H-abstraction from DMPO.

The effect of cations on the anomeric equilibrium of d-glucose in aqueous solutions — a raman-spectral study

Raman spectra of α- and β- d-glucose, each freshly dissolved in water, have been recorded. These conditions allow a more definite assignment of features to a particular anomer in the equilibrated mixture than is possible from a comparison with the spectra of the polycrystalline solids. A survey of the effect of metal cations on the α-β equilibrium of d-glucose has been carried out, using bands in the 950-800 cm −1 region to monitor the change. The Ca 2+ ion has a makred effect, shifting the equilibrium to favor the α anomer. For other cations, the effect has been found to fall off in magnitude according to the series ▪

Formation and polymerisation of malonaldehyde during irradiation of aqueous solutions of d-glucose and lactose with ultrasound

Irradiation with ultrasound, vigorous stirring, or vibration of aqueous solutions of d-glucose and lactose can induce chemical reactions. Malonaldehyde has been identified as one product, and the influence of pH and gas atmosphere on its formation by irradiation with ultrasound has been investigated. Only traces were present in neutral solutions, but it was a major product in alkaline solutions. Malonaldehyde is unstable, especially in neutral and acidic solutions, and gives 1,3,5-benzentricarbaldehyde by 1,2-addition and 1 by 1,4-addition. There is evidence that cyclic structures also exist, the ring closure being brought about by an additional hemiacetal bond. To some extent also, 1,3,5-benzenetricarbaldehyde is incorporated into the oligomers.

Maillard reaction products formed from D-glucose and glycine and the formation mechanisms of amides as major components.

Equimolar aqueous solutions of d-glucose and glycine were heated at 50°C and 95°C at pH 6.7. The headspace volatiles and the ether extracts from the reaction mixture were analyzed by gas chromatography and gas chromatography-mass spectrometry, using a fused silica capillary column. The major components formed were identified as diacetyl, furfuryl alcohol, two pyrroles, one pyranone and two amides. In order to elucidate the formation mechanisms of the amides formed from amino-carbonyl reactions, two model systems were adopted. N-Butylacetamide and N-butylformamide were formed as major components from diacetyl-butylamine and glyoxalbutylamine systems, respectively. The results obtained suggest that such α-dicarbonyls as 3-deoxyosone, 1-deoxy-d-erythro-2,3-hexodiulose and diacetyl generated in the amino-carbonyl reaction react with amino compounds, amides then being formed by cleavage of the C-C bond in the a-dicarbonyls.

Maillard reaction products from D-glucose and butylamine.

Equimolar aqueous solutions of D-glucose and n-butylamine were heated at 95°C for various times at pH 4, 6.5 and 11.48. The resulting brown solutions were extracted with ether. The volatile components in the ether extracts were analyzed by gas chromatography and gas chromatographymass spectrometry, with a fused silica capillary column. The major components formed were identified as three alcohols, four N-butylpyrroles, N-butylacetamide, N-butylformamide, N-butylsuccinimide, one pyranone and 5-(hydroxymethyl)-2-furfural. In addition, eleven minor components were also identified. The relative amount of each component changed markedly with pH. At pH 4.0, higher-boiling heterocyclic compounds without C-C fission of glucose were largely formed, and at pH 11.48, lower-boiling fission compounds were mainly formed. Both were observed in the reaction at pH 6.5.

Viscosities of concentrated solutions of sodium and potassium acetates in aqueous solutions of d-glucose

The relative viscosities (η r) of concentrated solutions of sodium and potassium acetates in 0.5 m d-glucose solution at 25, 30, 35, and 40° are reported. Viscosity data have been analyzed using Vand's, Thomas's, Bresslau and Miller's, Moulik's, and a generalized treatment, at higher electrolytic concentrations. The molar volumes ( V̄), ionic B-coefficients (B ±), and hydration numbers (n B) of ions were computed, and structural aspects of sodium and potassium acetates in aqueous d-glucose solutions have been interpreted by taking into account the magnitude of various parameters obtained. The temperature-dependence of B-coefficients has also been discussed. In aqueous d-glucose solutions, Na + and K + are found to act as net structure-breakers, whereas a significant structure-making trend is shown by acetate ion.

Electrokinetic studies of the testosterone-aqueous d-glucose interface

Electro-osmosis and streaming-potential measurements were made across a testosterone-plug membrane, using water and aqueous solutions of d-glucose as permeants. The electrophoretic velocity of testosterone particles dispersed in these solutions was also measured, experiments being confined to the range where linear flux-force relationships hold. Phenomenological coefficients were evaluated by using these linear relations, and the results analyzed inthe light of the thermodynamics of irreversible processes. Saxen's relationship holds between electro-osmosis and streaming potential. Concentration dependence of the various phenomenological coefficients was also examined. Cross-phenomenological coefficients were found to decrease with increase in the concentration of d-glucose solutions. The results are explained on the basis of strong hydrogen-bonding between d-glucose and the surrounding water molecules. Such membrane parameters as pore size, average number of pores, and the membrane constant were evaluated. Electro-osmotic and electrophoretic data were used to estimate the zeta potential, in order to characterize the membrane-permeant interface. The dependence of the zeta potential on the concentration was also examined.

Free Energy, Enthalpy, and Entropy Changes of Mixing of Aqueous Solutions of d-Glucose and Tetraalkylammonium Bromide at 25 °C

Abstract Changes of free energy and enthalpy of mixing of aqueous solutions of d-glucose and tetraalkylammonium bromide were measured at 25 °C by isopiestic method and calorimetry, and excess thermodynamic quantities and transfer functions were calculated. All transfer functions were positive and mutual salting-out was observed. The positive value of free energy of transfer of tetrabutylammoniun bromide from water to aqueous d-glucose solution comes from the predominance of enthalpic term over entropic term. These results are interpreted in terms of the structural incompatibility of hydration cospheres around these two kinds of solutes.

Permeability studies on animal membrane/carbohydrate systems

Hydrodynamic permeability measurements on water, and on aqueous solutions of d-glucose and sucrose of various concentrations, through frog-skin membrane were made. The conductance of the membrane equilibrated with the permeants was also measured. Some comments regarding the dependence of the permeability coefficient and the membrane conductance on the concentration were made. It was observed that the membrane behaves anisotropically in so far as the hydrodynamic permeability is concerned.

Laser-raman spectra of d-glucose and sucrose in aqueous solution

Laser-Raman spectra of d-glucose in water at various concentrations were recorded below 1700 cm −1. Assignments of the frequencies of d-glucose were proposed, based on earlier work on the vibrational spectra of this sugar, and determination by other techniques of the anomeric composition of aqueous solutions of d-glucose. The proportions of the anomers found from the ratio of the Raman intensities for the same models of vibrations were similar to those found by other techniques. Assignments of the frequencies for sucrose were proposed, in the light of previous results on d-glucose and d-fructose, and the effect, on their Raman spectra, of the condensation of these two monosaccharides was pointed out.

Radical-induced deamination of 2-amino-2-deoxy- d-glucose in aqueous solution

2-Amino-2-deoxy- d-glucose (10mM) as the free base (pH 8.5) and the hydrochloride (pH 5) were γ-irradiated in aqueous solution under deoxygenated (N 2O-saturated) and oxygenated [N 2O/O 2(4:1)-saturated] conditions. Ammonia and 18 nitrogen-free products were identified and their G-values determined. Mechanisms for the radical-induced deamination are proposed. The radicals centered at C-1, C-2, C-3, and the nitrogen are suggested as initiators in the deamination processes.

Free Radical Induced Oxidation of Neutral Aqueous Solutions of D-Glucose in the Presence of Oxygen - a Non-Chain Process

Abstract Oxygenated 1M aqueous solutions of 2-methyltetrahydrofuran (MTHF) or D-glucose were γ-irradiated, and G(total peroxide) was determined as a function of dose rate and temperature. Whereas MTHF was oxidized by a chain process, D-glucose was not. The peroxyl radicals derived from D-glucose rapidly eliminate HO2·. At natural pH HO2·(pK=4.75) is largely deprotonated. O2- does not propagate a chain.