Ionization of ethylene glycol in isodielectric acetonitrile + ethylene glycol mixtures at 25 °C

1979 ◽  
Vol 57 (18) ◽  
pp. 2470-2475 ◽  
Author(s):  
Kumardev Bose ◽  
Kiron K. Kundu
Keyword(s):  
Free Energy ◽  
Ethylene Glycol ◽  
Mixed Solvents ◽  
Solvent Composition ◽  
Free Energies ◽  
Emf Measurements ◽  
Free Energies Of Transfer ◽  
Mixed Systems

The autoprotolysis constants (Ksm) of ethylene glycol in isodielectric acetonitrile + ethylene glycol mixtures have been determined at 25 °C from emf measurements on the cell[Formula: see text]From these values, those of δΔG0, the free energy of ionization of ethylene glycol in these mixed solvents relative to that in pure glycol, have been computed. The nature of variation of δΔG0 with solvent composition has been compared with that in two other mixed systems: water + ethylene glycol and methanol + 1,2-propanediol and the intrinsic differences between the solvation characteristics of the various solvents have been pointed out. The standard free energies of transfer of the glycoxide ion, ΔGt0(OEg−), from pure glycol to acetonitrile + glycol mixtures have also been estimated using ΔGt0(H+) values obtained earlier. The glycoxide ion is increasingly desolvated as the acetonitrile content of the solvent increases, as indicated by increasingly positive values of ΔGt0(OEg−). This behaviour has been compared with those of ΔGt0(H+) and ΔGt0(Cl−) determined previously.

Determination of absolute transfer free energies of hydroxyl ion from water to aqueous 2-methoxy ethanol

1981 ◽  
Vol 59 (7) ◽  
pp. 1153-1159 ◽  
Author(s):  
Abhijit Bhattacharya ◽  
Asim K. Das ◽  
Kiron K. Kundu
Keyword(s):  
Ethylene Glycol ◽  
Mixed Solvents ◽  
Aqueous Mixtures ◽  
Free Energies ◽  
Free Energies Of Transfer ◽  
Hydroxyl Ion ◽  
Relative Stabilization ◽  
Solvent Systems ◽  
Reference Electrolyte

Absolute standard free energies of transfer ΔGt0 of OH− from water to aqueous mixtures of 2-methoxy ethanol (ME) have been evaluated at 298.15 K by combining the apparent transfer free energies of the lyate ion that were obtained from the standard emf's of the double cell:[Formula: see text]and that from the autoionization constants of these mixed solvents determined by use of the cell comprising H2– and Ag–AgCl electrodes. The required ΔGt0 values of K+ and H+ were determined earlier using the well-known tetraphenyl arsonium tetraphenyl boride (TATB) reference electrolyte method. These values and their non-Born type contributions in particular, are found to be increasingly positive in water-rich compositions, indicating that the relative stabilization of OH− and the acidity of the mixed solvents decrease with increasing cosolvent composition. These, when compared with those in aqueous mixtures of ethylene glycol and 1,2-dimethoxy ethane, are found to lie intermediate between the latter solvent systems conforming to what is expected from the structural and electronic features of the cosolvents.

Thermodynamics of autoionization of aqueous tetrahydrofuran and 1,2-dimethoxyethane and the structuredness of solvents

1981 ◽  
Vol 59 (22) ◽  
pp. 3141-3148 ◽  
Author(s):  
Jayati Datta ◽  
Kiron K. Kundu
Keyword(s):  
Free Energy ◽  
Mixed Solvents ◽  
Relative Size ◽  
Water Structure ◽  
Aqueous Mixtures ◽  
Free Energies ◽  
Emf Measurements ◽  
Energy Data ◽  
Size And Shape ◽  
Relative Free Energy

Autoionization constants (Ks) of aqueous mixtures of tetrahydrofuran (THF) and 1,2-dimethoxyethane (DME) containing 10, 30, and 50 wt.% cosolvent in each case have been determined from emf measurements of the cell: Pt, H2 (g, 1 atm)|KOH (m1), KBr (m2), solvent|AgBr, Ag at seven equidistant temperatures ranging from 5 to 35 °C. The standard free energies (ΔG0), entropies (ΔS0), and enthalpies (ΔH0) of autoionization of the solvents were also evaluated from these data. Relative free energy data, δΔG0(≡sΔG0 − wΔG0), for these solvents as well as those for dioxane (D) – water mixtures taken from the literature, when coupled with the previously determined transfer free energies of H+, ΔGt0(H+), yielded ΔGt0(OH−)app (≡ΔGt0(OH−) − ΔGt0(H2O)) values in the mixed solvents. Relative magnitudes of ΔGt0(H+) and ΔGt0(OH−)app and their non-Born parts, ΔGt,ch0(H+) and ΔGt,ch0(OH−)app in particular, suggest that the "basicity" of these aqueous cosolvents decreases in the order DME > THF > D and their "acidity" in the reverse order, as expected from structural and electronic consideration of these cosolvent molecules. Analysis of the relative entropie contributions, Tδ (ΔS0) (≡T (sΔS0 − wΔS0), for the autoionization of these aqueous cosolvents and in particular ΔSt0(H2O) values derived there from, suggests that while THF promotes three dimenstional (3D) ice-like water structures at initial compositions and D induces breakdown of the 3D structures right from the beginning, DME breaks down water structures at initial compositions, but induces some order around 4–14 mol% DME by forming the possible H-bonded bidentate DME–water complexes. And beyond certain compositions, depending upon the relative size and shape, all the cosolvents break down water structure due to packing imbalance.

Thermodynamics of autoionization of 2-methoxy ethanol + water mixtures and structuredness of the solvents

1985 ◽  
Vol 63 (4) ◽  
pp. 804-808 ◽  
Author(s):  
Prabir K. Guha ◽  
Kiron K. Kundu
Keyword(s):  
Dielectric Constant ◽  
Ethylene Glycol ◽  
Structural Changes ◽  
Mixed Solvents ◽  
Three Dimensional ◽  
Aqueous Mixtures ◽  
Free Energies ◽  
Acid Base ◽  
Emf Measurements ◽  
Structure Breaking

Standard free energies (ΔG0) and entropies (ΔS0) of autoionization of aqueous mixtures of 10, 30, 50, and 70 wt.% of 2-methoxy ethanol (ME) have been evaluated from the autoionization constants (Ks) of the solvents as determined from emf measurements of the cell Pt, H2 (g, 1 atm)/KOH (m1), KBr (m2), solvent/AgBr–Ag at seven equidistant temperatures ranging from 15 to 45 °C. The observed increase in pKs and the related δ(ΔG0) (= sΔG0 − wΔG0) has been ascribed to be the effect of decreased dielectric constant, increased basicity and decreased acidity of the mixed solvents compared to that of water. Analysis of relative entropic contributions of autoionization, Tδ(ΔS0) (= T(sΔS0 − wΔS0)) and their chemical part, Tδ(ΔS0)ch in the aqueous mixtures of ME as well as the closely related cosolvents like ethylene glycol (EG) and 1,2-dimethoxy ethane (DME), appears to suggest that unlike EG but like DME, ME has an overall structure breaking propensity of three dimensional (3D) tetrahedral structures of water. But the transfer entropies of water ΔSt0(H2O) derived thereof, for these cosolvents suggest that while the structural changes induced by protic EG are seemingly obseured due to the involved multiple acid-base equilibria with water, and that by aprotic DME are disturbed by the formation of strong hydrogen-bonded DME–H2O complexes around 4–14 mol% DME, quasi-aprotic ME appears to induce some order due to the possible formation of H-bonded ME–water complexes around 10–15 mol% ME.

Free energies and entropies of transfer of hydrogen halides from water to aqueous 2-methoxy ethanol and structuredness of the solvents

1985 ◽  
Vol 63 (4) ◽  
pp. 798-803 ◽  
Author(s):  
Prabir K. Guha ◽  
Kiron K. Kundu
Keyword(s):  
Dielectric Constant ◽  
Mixed Solvents ◽  
Three Dimensional ◽  
Halide Ions ◽  
Aqueous Mixtures ◽  
Free Energies ◽  
Hydrogen Halides ◽  
Emf Measurements ◽  
Composition Profiles ◽  
The Individual

Standard free energies (ΔGt0) and entropies (ΔSt0) of transfer of HBr and HI from water to some aqueous solutions of 2-methoxy ethanol (ME) have been determined from emf measurements of the cells: Pt, H2 (g, 1 atm)/HBr (m), solvent/AgBr–Ag and Pt, H2 (g, 1 atm)/KOH (m1), KI (m2), solvent/AgI–Ag, respectively, at seven equidistant temperatures ranging from 15 to 45 °C. ΔGt0 values of HBr and HI as well as of HCl obtained from literature, and particularly that of the individual ions obtained by tetraphenylarsonium tetraphenylboron (TATB) assumption, suggest that while H+ is increasingly stabilized by cosolvent-induced larger "basicity", halide ions (X−) are increasingly destabilized by cosolvent-induced decreased "acidity" and the dielectric constant of the mixed solvents compared to that of water. Analysis of the variation of the observed TΔSt0(HX) and particularly of ΔY (= TΔSt0(H+) + TΔS0t.ch (X−), with composition, in the light of Kundu etal's semi-quantitative theory reveals that ME induces breakdown of three dimensional (3D) tetrahedral structures of water at water-rich compositions. This is being followed by an ordered region due to possible H-bonded cosolvent–water complexation and then the usual disordered region due to packing imbalance. Comparison of ΔY(HI)–composition profiles for aqueous mixtures of t-butanol (ButOH), ethylene glycol (EG), and 1,2-dimethoxy ethane (DME) also demonstrates that the remarkable enhancement of 3D water structures by the well known structure promoter ButOH gets succintly diminished when cosolvent ButOH is replaced by EG, ME, and DME, as is expected from structural and electronic considerations of the cosolvents.

scholarly journals Adsorption phenomena at the interface between mercury and solutions containing choline chloride, ethylene glycol and water

2021 ◽  
pp. 50-58
Author(s):  
F.I. Danilov ◽  
◽  
Y.D. Rublova ◽  
V.S. Protsenko ◽  
◽  
...  
Keyword(s):  
Free Energy ◽  
Ethylene Glycol ◽  
Choline Chloride ◽  
Specific Interaction ◽  
Mercury Electrode ◽  
Deep Eutectic Solvent ◽  
Deep Eutectic Solvents ◽  
Charged Surface ◽  
Free Energies ◽  
Adsorption Phenomena

Adsorption of the components of deep eutectic solvent ethaline (ethylene glycol and choline chloride) on mercury electrode is investigated by electrocapillary measurements. It is determined that choline cations are mainly adsorbed on the negatively charged surface of mercury, while chloride anions are mainly adsorbed on the positively charged surface. The corresponding values of free energies of adsorption and interactions of adsorbate and solvent with metal are calculated and analyzed. An anomalous increase in both the apparent value of the adsorption at limiting coverage and the free energy of the interaction of the choline cation with mercury is observed in the transition from aqueous to ethylene glycol solutions, which is explained by the formation of complexes in a surface layer that exist in deep eutectic solvents and are capable of adsorbing on the electrode surface. The free energy of interaction with the mercury surface is higher than the energy of squeezing out from the volume of the solution onto its surface, which indicates the specific interaction of the adsorbate with mercury. A marked decrease in interfacial tension on both branches of the electrocapillary curve is observed when water is added to ethaline.

Transfer Gibbs Free Energies of Divalent Anions from Water to Organic and Mixed Aqueous-OrganicSolvents

1995 ◽  
Vol 50 (1) ◽  
pp. 51-58 ◽  
Author(s):  
Y. Marcus
Keyword(s):  
Hydrogen Bonding ◽  
Ethylene Glycol ◽  
Free Energies ◽  
Free Energies Of Transfer ◽  
Protic Solvents

The standard molar Gibbs free energies of transfer of divalent anions, in particular sulfate, from water into methanol, ethanol, ethylene glycol, dioxane, tetrahydrofuran, acetone, N-methylformamide, N,N-dimethylformamide, pyridine, acetonitrile, and dimethylsulfoxide and mixtures of some of them with water or some other solvent have been obtained from the literature. The tetraphenylarsonium tetraphenylborate extrathermodynamic assumption has been used as far as possible in order to obtain the single ion values. The generally unfavorable transfers from water (or protic solvents) into polar aprotic ones are interpreted in terms of the properties of the anions and of the solvents, dominated by the hydrogen-bonding acidity of water.

Activity coefficients and standard Gibbs free energies of transfer of NaCl and KCl from water to aqueous solution of 2-butoxyethanol by EMF studies

1993 ◽  
Vol 71 (12) ◽  
pp. 2038-2042 ◽  
Author(s):  
Yvonne MacPherson ◽  
R. Palepu
Keyword(s):  
Activity Coefficients ◽  
Empirical Equation ◽  
Glass Electrode ◽  
Free Energies ◽  
Selective Electrode ◽  
Cell Potential ◽  
Emf Measurements ◽  
Free Energies Of Transfer ◽  
The Mean ◽  
Mean Activity Coefficients

From the emf measurements of the cell Na- or K-glass electrode|2-butoxyethanol, H2O, NaCl or KCl|Cl ion-selective electrode, the standard potentials were determined at 298 K for five different compositions of the solvent. From the emf data the mean activity coefficients of NaCl and KCl were calculated and fitted to an empirical equation. The standard Gibbs free energies of transfer of NaCl and KCl from water to mixtures of water and 2-butoxyethanol were calculated from the cell potential.

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