van't Hoff Based Thermodynamics

Varani, Katia; Gessi, Stefania; Merighi, Stefania; Borea, Pier Andrea

doi:10.1002/9783527673025.ch2

Cited by 5 publications

(3 citation statements)

References 46 publications

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“…The preference of the trans over the cis conformation at the amide θ 2 torsion angle was investigated by analyzing ln K eq vs 1/ T , where T is the absolute temperature in Kelvin, in a van’t Hoff plot (Figure ). By assuming that the Δ H of the reaction is temperature independent, Δ H and Δ S can be calculated by linear regression in which the negative slope and the y-intercept of the fitted line corresponds to Δ H and Δ S , respectively, both divided by the gas constant.…”

Section: Resultsmentioning

confidence: 99%

Conformational Dynamics and Exchange Kinetics of N-Formyl and N-Acetyl Groups Substituting 3-Amino-3,6-dideoxy-α-d-galactopyranose, a Sugar Found in Bacterial O-Antigen Polysaccharides

et al. 2017

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Three dimensional shape and conformation of carbohydrates are important factors in molecular recognition events and the N-acetyl group of a monosaccharide residue can function as a conformational gatekeeper whereby it influences the overall shape of the oligosaccharide. NMR spectroscopy and quantum mechanics (QM) calculations are used herein to investigate both the conformational preferences and the dynamic behavior of N-acetyl and N-formyl substituents of 3-amino-3,6-dideoxy-α-d-galactopyranose, a sugar and substitution pattern found in bacterial O-antigen polysaccharides. QM calculations suggest that the amide oxygen can be involved in hydrogen bonding with the axial OH4 group primarily but also with the equatorial OH2 group. However, an NMR J coupling analysis indicates that the θ torsion angle, adjacent to the sugar ring, prefers an ap conformation where conformations <180° also are accessible, but does not allow for intramolecular hydrogen bonding. In the formyl-substituted compound J coupling constants to the exo-cyclic group were detected and analyzed. A van't Hoff analysis revealed that the trans conformation at the amide bond is favored by ΔG° ≈ - 0.8 kcal·mol in the formyl-containing compound and with ΔG° ≈ - 2.5 kcal·mol when the N-acetyl group is the substituent. In both cases the enthalpic term dominates to the free energy, irrespective of water or DMSO as solvent, with only a small contribution from the entropic term. The cis-trans isomerization of the θ torsion angle, centered at the amide bond, was also investigated by employing H NMR line shape analysis andC NMR saturation transfer experiments. The extracted transition rate constants were utilized to calculate transition energy barriers that were found to be about 20 kcal·mol in both DMSO-d and DO. Enthalpy had a higher contribution to the energy barriers in DMSO-d compared to in DO, where entropy compensated for the loss of enthalpy.

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Section: Resultsmentioning

confidence: 99%

Conformational Dynamics and Exchange Kinetics of N-Formyl and N-Acetyl Groups Substituting 3-Amino-3,6-dideoxy-α-d-galactopyranose, a Sugar Found in Bacterial O-Antigen Polysaccharides

et al. 2017

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“…6. Where,

{{K}_{L}}

(mL.mmol −1 ) is the Langmuir constant, R (J.mol −1 .K −1 ) is the gas constant, and T (K) is the temperature [64,69,70]

\vcenter{\openup.5em\halign{$\displaystyle{#}$\cr ln{K}_{L}={{{\rm \Delta }S}\over{R}}-{{{\rm \Delta }H}\over{RT}}\hfill\cr}}

\vcenter{\openup.5em\halign{$\displaystyle{#}$\cr \Delta G=\Delta H-T\Delta S\hfill\cr}}

…”

Section: Methodsmentioning

confidence: 99%

“…Where, K L (mL.mmol À 1 ) is the Langmuir constant, R (J.mol À 1 .K À 1 ) is the gas constant, and T (K) is the temperature. [64,69,70]…”

Section: Thermodynamic Studiesmentioning

confidence: 99%

Thiourea Adsorbent for Efficient Removal of Mercury (II)

El Khoueiry,

Giusti,

Lelong

et al. 2023

ChemistrySelect

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The removal of heavy toxic metals from industrial effluents is extremely important, especially for mercury (Hg), which is classified as a highly toxic even at low concentrations. For this purpose, novel thiourea chelating resins were synthesized as sorbent for Hg (II). Six different polymers of formo‐phenolic types were characterized and evaluated for their chelating properties with respect to Hg (II) extraction. Batch adsorption studies of mercury (II) as a function of pH, initial metal ion concentration, temperature, and time showed that thiourea formo‐phenolic polymers have a good affinity for Hg removal and a high adsorption capacity. Adsorption isotherms (Langmuir and Freundlich) and kinetic models (pseudo‐first and pseudo‐second order) were used to interpret the sorption behavior of the materials. The Langmuir model yielded the best fit with a maximum adsorption capacity of 300 mg/g. Desorption studies were performed with aqueous thiourea solution and showed that the adsorbent is indeed regenerable and can be effectively used for up to three adsorption‐desorption cycles with negligible loss of performance. This study confirmed the potential of thiol‐modified formo‐phenolic resins in sorbent engineering with promising applications in the remediation of mercury‐contaminated water.

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