13C NMR measurements of acid-base equilibrium constants in alkaline aqueous solutions of D-glucose anomers

Popov, Konstantin; Sultanova, N. M.; Rönkkömäki, Hannu

doi:10.1134/s0036024406100232

Cited by 4 publications

(2 citation statements)

References 8 publications

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“…Compared to our previous work, we find that the glucosamidefunctionalized fused silica/water interface is around four times more negatively charged than carboxylic acid-functionalized fused silica/water interfaces held at pH 7 (-0.0003 C/m 2 ) 80 but around ten times less negatively charged than the bare fused silica/water interface (-0.013 C/m 2 ). 81 Since the glucose functionality does not bear any negative charge from deprotonated hydroxyl groups at pH 7, 82 the slight negative interfacial charge density suggests that the glucosamide-functionalized fused silica surface possesses residual unreacted SiOH surface sites. Estimating that only 20% of unreacted surface sites are deprotonated at pH 7, 83 we calculate that approximately 96% of all silanol sites (protonated, neutral, and deprotonated) formed covalent bonds with the trichlorosilane during the first step of the functionalization.…”

Section: Resultsmentioning

confidence: 99%

Zinc Interactions with Glucosamine-Functionalized Fused Silica/Water Interfaces

et al. 2010

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The adsorption of Zn2+ to glucosamide-functionalized fused silica/water interfaces is studied using second harmonic generation (SHG). We characterize each step of the surface functionalization using vibrational sum frequency generation (SFG) and X-ray photoelectron spectroscopy (XPS), where specific vibrational modes in the C−H region and binding energies in the C1s and N1s region are determined to be indicative of glucose covalently tethered to the surface. We employ the SHG χ(3) technique to track Zn2+ adsorption and desorption directly at the glucosamide-functionalized fused silica/aqueous interface at pH 7 and 10 mM NaCl and determine the electrostatic and thermodynamic binding parameters using standard electrical double layer models to quantify the change in interfacial potential upon zinc adsorption. The results presented here allow for the possibility of 2:1 to 3:1 carbohydrate:metal coordination complexes and suggest the possibility for multivalent interactions which have not been observed with glucose in the bulk aqueous phase, where 1:1 complexes dominate. These findings suggest that interactions between metal ions and carbohydrate arrays may be much stronger at interfaces as opposed to the bulk phase, with direct implications for controlling and predicting coordination chemistry.

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Section: Resultsmentioning

confidence: 99%

Zinc Interactions with Glucosamine-Functionalized Fused Silica/Water Interfaces

et al. 2010

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“… a p K a values are obtained according to Jencks, except for glucose . p K a values for glucose indicated the C1 carbon as the most likely choice of protonation . No values were found for C6.…”

Section: Resultsmentioning

confidence: 99%

Anomeric Effect in “High Energy” Phosphate Bonds. Selective Destabilization of the Scissile Bond and Modulation of the Exothermicity of Hydrolysis

et al. 2008

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A natural bonding orbital (NBO) analysis of phosphate bonding and connection to experimental phosphotransfer potential is presented. Density functional calculations with the 6-311++G(d,p) basis set carried out on 10 model phosphoryl compounds verify that the wide variability of experimental standard free energies of hydrolysis (a phosphotransfer potential benchmark) is correlated with the instability of the scissile O-P bond through computed bond lengths. NBO analysis is used to analyze all delocalization interactions contributing to O-P bond weakening. Phosphoryl bond lengths are found to correlate strongest (R = 0.90) with the magnitude of the ground-state n(O) --> sigma*(O-P) anomeric effect. Electron-withdrawing interactions of the substituent upon the sigma(O-P) bonding orbital also correlate strongly with O-P bond lengths (R = 0.88). However, an analysis of sigma*(O-P) and sigma(O-P) populations show that the increase in sigma*(O-P) density is up to 6.5 times greater than the decrease in sigma(O-P) density. Consequently, the anomeric effect is more important than other delocalization interactions in impacting O-P bond lengths. Factors reducing anomeric power by diminishing either lone pair donor ability (solvent) or antibonding acceptor ability (substituent) are shown to result in shorter O-P bond lengths. The trends shown in this work suggest that the generalized anomeric effect provides a simple explanation for relating the sensitivity of the O-P bond to diverse environmental and substituent factors. The anomeric n(O) --> sigma*(O-P) interaction is also shown to correlate strongly with experimentally determined standard free energies of hydrolysis (R = -0.93). A causal mechanism cannot be inferred from correlation. Equally, a P-value of 1.2 x 10(-4) from an F-test indicates that it is unlikely that the ground-state anomeric effect and standard free energies of hydrolysis are coincidentally related. It is found that as the exothermicity of hydrolysis increases, the energy stabilization of the ground-state anomeric effect increases with selective destabilization of the high-energy O-P bond to be broken in hydrolysis. The anomeric effect therefore partially counteracts a larger resonance stabilization of products that makes hydrolysis exothermic and needs to be considered in achieving improved agreement between calculated and empirical energies of hydrolysis. The avenues relating the thermodynamic behavior of phosphates to underlying structural factors via the anomeric effect are discussed.

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Syntheses of difluorinated carbasugar phosphates from trifluoroethanol

et al. 2009

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Difluorinated cyclohexene diols (prepared from trifluoroethanol) can be elaborated to racemic analogues of phosphorylated sugars via regioselective protection and phosphorylation of the exposed C-1 hydroxyl group. Cis-diol protection was achieved using stannylene methodology, though the regioselectivity depended on the orientation of the methyl group at C-5. UpJohn dihydroxylation is effective with the phosphotriester in place and global deprotection to the tetrol monophosphates is efficient.

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13C NMR measurements of acid-base equilibrium constants in alkaline aqueous solutions of D-glucose anomers

Cited by 4 publications

References 8 publications

Zinc Interactions with Glucosamine-Functionalized Fused Silica/Water Interfaces

Zinc Interactions with Glucosamine-Functionalized Fused Silica/Water Interfaces

Anomeric Effect in “High Energy” Phosphate Bonds. Selective Destabilization of the Scissile Bond and Modulation of the Exothermicity of Hydrolysis

Syntheses of difluorinated carbasugar phosphates from trifluoroethanol

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