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.

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 solutions of tetrahydrofuran, dioxane, and 1,2-dimethoxyethane and the structuredness of the solvents

1981 ◽  
Vol 59 (22) ◽  
pp. 3149-3156 ◽  
Author(s):  
Jayati Datta ◽  
Kiron K. Kundu
Keyword(s):  
Aqueous Solutions ◽  
Mixed Solvents ◽  
3D Structure ◽  
Relative Order ◽  
Halide Ions ◽  
Free Energies ◽  
Composition Profiles ◽  
Solvent Systems ◽  
The Individual ◽  
Soft Interactions

Standard free energies (ΔGt0) and entropies (ΔSt0) of transfer of hydrogen iodide from water to some aqueous solutions of tetrahydrofuran (THF), dioxane (D), and 1,2-dimethoxyethane (DME) have been determined by measuring the emf's of the cell: Pt, H2 (g, 1 atm)|KOH (m1), KI (m2), solvent|AgI, Ag at seven equidistant temperatures ranging from 5 to 35 °C. In each of these ethereal solvent systems ΔGt0 values of HI, as well as of HCl and HBr obtained from the literature, and particularly of the individual ions, suggest that while H+ is increasingly stabilized, halide ions are increasingly destabilized due to the influence of cosolvent-induced larger "basicity" and smaller "acidity" of the mixed solvents compared to that of water, and both conformed to the expected order: D < THF < DME. Moreover, the relative order: Cl− > Br− > I− in all the solvent systems is ascribable to the combined effects of "acid–base" and "soft–soft" interactions and the superimposed quadrupolar interactions in the case of D and the charge transfer to solvent (CTTS) complexation effect, especially on I− in the case of THF. Analysis of the entropie contributions, TΔSt0, and particularly of the relative order of ΔY (≡TΔSt0(H+) + TΔSt,ch0(X−)) for X = Cl, Br, and I, in the light of the semi-quantitative theory proposed earlier by Kundu et al., reveals that at initial compositions, while THF promotes 3D structures of water, both D and DME break down the same; at higher compositions all the cosolvents disrupt the structure as usual due to packing imbalance. The nature and relative positions of ΔY–composition profiles also suggest that while increase of hydrophobic groups of the cosolvents increases the stabilization, increase in hydrophilicity or H-bonding sites decreases the stabilization of the 3D structure of water.

Solvent effect on the dissociation of p-nitroanilinium ion in glycerol–water media at 25 °C

1984 ◽  
Vol 62 (11) ◽  
pp. 2245-2248
Author(s):  
Amrita Lal De ◽  
Tapas Kumar De
Keyword(s):  
Solvent Effect ◽  
Dissociation Constants ◽  
Mixed Solvents ◽  
Individual Species ◽  
Aqueous Mixtures ◽  
Free Energies ◽  
Monohydric Alcohol ◽  
Glycerol Water ◽  
Alcohol Water ◽  
The Individual

Thermodynamic dissociation constants (sK) of p-nitroanilinium ion (BH+) have been determined at 25 °C in aqueous mixtures of 10, 30, 50, 70, and 90 wt.% of glycerol (GL) by spectrophotometric measurements. Standard free energies, [Formula: see text], of p-nitroaniline (B) from water to mixed solvents have been evaluated from the measurement of solubilities at 25 °C. p(sK) values decrease with increase in mol% of GL and pass through a minimum and then increase very slowly. The solvent effect on the dissociation, δ(ΔG0) = 2.303RT [p(sK)N – p(wK)N] has been discussed in terms of the standard free energies of transfer [Formula: see text] from water to aqueous mixtures of GL of the uncharged base (B), the hydrochloride of the base (BHCl), hydrochloric acid (HCl), and also in terms of the individual species involved in the dissociation process. The solvent effect in trihydric alcohol – water (GL + H2O) system has been compared with those in dihydric alcohol – water (ethylene glycol + water) and monohydric alcohol – water (ethanol + water) systems available from literature. The much less solvent effect in GL + H2O has been primarily attributed to the contrasting nature of interaction of H+ and of partially charged H atoms of—NH3+ group in BH+ compared to those in other two solvent systems.

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.

Ion–ion–solvent interactions in aqueous ionic cosolvent systems. IV. Transfer energetics of water, p-nitroaniline, and benzoic acid from emf/solubility measurements at different temperatures in aqueous sodium nitrate solvent system

1988 ◽  
Vol 66 (3) ◽  
pp. 469-475
Author(s):  
Sibaprasad Rudra ◽  
Himansu Talukdar ◽  
Kiron K. Kundu
Keyword(s):  
Benzoic Acid ◽  
Sodium Nitrate ◽  
Solvent System ◽  
Aqueous Mixtures ◽  
Free Energies ◽  
Salting Out ◽  
Emf Measurements ◽  
Solvent Interactions ◽  
Different Temperatures ◽  
Composition Profiles

Autoionization constants (Ks) of aqueous mixtures of 1, 2, and 4 m sodium nitrate used as an ionic cosolvent system have been determined from emf measurements of the cell: Pt, H2 (g, 1 atm)/KOH (m1) KCl (m2), solvent/AgCl–Ag at five equidistant temperatures ranging from 15–35 °C. The standard free energies (ΔG0) and entropies (ΔS0) of autoionisation of the solvents were then evaluated from these data. Relative free energies (ΔG0) and entropies of (ΔS0)of autoionization of the solvents when coupled with the previously determined transfer free energies [Formula: see text] and entropies [Formula: see text] of H+ yielded [Formula: see text][Formula: see text],[Formula: see text] and [Formula: see text]. Values of [Formula: see text] and [Formula: see text] obtained after correcting for [Formula: see text], as well as [Formula: see text] and [Formula: see text]obtained after correcting the "cavity effect" and Born-type electrostatic effect suggests that while the "basicity" of the aqueous NaNO3 solutions decreases, the "acidity" more or less increases with NaNO3 concentration. The observed [Formula: see text]– and [Formula: see text]–composition profiles were also examined in the light of Kundu et al.'s four-step transfer process and the involved order–disorder phenomena, respectively, as proposed earlier.Standard free energies [Formula: see text] and entropies [Formula: see text] of transfer of p-nitroaniline (pNA) and benzoic acid (HBz) for the solvent system have also been determined from solubility measurements at different temperatures. The observed [Formula: see text]–and [Formula: see text]–composition profiles appear to reflect the salting-out effect of the salt and the [Formula: see text]–and [Formula: see text]–composition profiles confirm the applicability of either of these quantities rather than [Formula: see text], as a better structural probe both for aquo-ionic and aquo-organic solvents.

Deprotonation and transfer energetics of glycine in aqueous mixtures of urea and glycerol from emf measurements at different temperatures

1989 ◽  
Vol 67 (2) ◽  
pp. 315-320 ◽  
Author(s):  
Himansu Talukdar ◽  
Sibaprasad Rudra ◽  
Kiron K. Kundu
Keyword(s):  
Scaled Particle Theory ◽  
Aqueous Mixtures ◽  
Free Energies ◽  
Emf Measurements ◽  
Transfer Energetics ◽  
Galvanic Cells ◽  
Aqueous Urea ◽  
Different Temperatures ◽  
Composition Profiles ◽  
Reference Electrolyte

Deprotonation constants, Ka(RH2+) and Ka(RH±), of glycine (RH±) have been determined at five equidistant temperatures ranging from 15 to 35 °C by measuring the emf of galvanic cells comprising Pt/H2 and Ag–AgCl electrodes in aqueous mixtures of protophilic protic urea (UH) and protophobic protic glycerol (GL). Medium effects on deprotonation of the acid: [Formula: see text] have been dissected into transfer free energies [Formula: see text] and entropies [Formula: see text] of the species involved as obtained by measuring the transfer energetics [Formula: see text] of RH± from solubility measurements at different temperatures and of H+ based on tetraphenylarsonium tetraphenylborate (TATB) reference electrolyte assumption determined earlier. The [Formula: see text] values obtained after due correction from the cavity effect based on scaled particle theory (SPT) and electrostatic effects including Born and ion–dipole effects for the charged species involved in the two deprotonation equilibria enable better understanding of the solvent effect on the deprotonation constants. Moreover, the [Formula: see text]–composition profiles are found to exhibit similar characteristic maxima and minima as for simple cations and anions in these solvent systems, thus providing useful information on the structural characteristic of these cosolvents. Keywords: deprotonation energetics, glycine, aqueous urea, aqueous glycerol, EMF measurements.

Gibbs energies of transfer of individual ions from water to acetone + water solvents

1989 ◽  
Vol 67 (8) ◽  
pp. 1268-1273 ◽  
Author(s):  
Mahmoud Mohamad Elsemongy ◽  
Ahmed Ahmed Abdel-Khalek
Keyword(s):  
Glass Electrode ◽  
Aqueous Mixtures ◽  
Free Energies ◽  
Emf Measurements ◽  
Gibbs Energies ◽  
Electrode Potentials ◽  
Gibbs Energies Of Transfer ◽  
Acetone Water ◽  
Alkali Metal Halides ◽  
Dipolar Aprotic Solvents

The standard absolute potentials of hydrogen, Ag–AgX (X = Cl, Br, and I) and M/M+ (M = Li, Na, K, Rb, and Cs) electrodes in nine different acetone + water solvents containing up to 80 wt. % acetone were determined from the emf data at 25 °C of the cells: glass electrode/HCl (m), solvent/AgCl–Ag and glass electrode (M)/MX (m), solvent/AgX–Ag. The standard Gibbs free energies of a transfer of halogen acids and alkali metal halides as well as their constituent individual ions from water to the respective solvents were computed. The observed increases in [Formula: see text] values of all ions with increasing acetone content of the solvent and their relative order in each solvent were interpreted and discussed. A comparison of the present results with those obtained earlier in the dimethyl sulphoxide (DMSO) + water solvents shows the different nature of the two dipolar aprotic solvents, acetone and DMSO, in their aqueous mixtures. Keywords: acetone + water solvents, electrode potentials, emf measurements, individual ions, transfer free energies.

Ion–ion–solvent interactions in aqueous ionic cosolvent systems. III. Thermodynamics of hydrogen bromide and hydrogen iodide from water to aqueous solutions of sodium nitrate from emf measurements at different temperatures and the structuredness of the solvents

1987 ◽  
Vol 65 (12) ◽  
pp. 2843-2848
Author(s):  
Sibaprasad Rudra ◽  
Himansu Talukdar ◽  
Kiron K. Kundu
Keyword(s):  
Sodium Nitrate ◽  
Structural Changes ◽  
Hydrogen Bromide ◽  
Scaled Particle Theory ◽  
Relative Order ◽  
Emf Measurements ◽  
Solvent Interactions ◽  
Different Temperatures ◽  
Composition Profiles ◽  
The Individual

Standard free energies [Formula: see text] and entropies [Formula: see text] of transfer of hydrogen bromide and iodide from water to the aqueous 1, 2, and 4 m of sodium nitrate have been determined by measuring the emf's of the cell: Pt, H2(g, 1 atm)/KOH(m1), KX(m2), solvent/AgX–Ag where X = Br or I at five equidistant temperatures ranging from 15–35°C. [Formula: see text] values of HBr, HI as well as that of HCl obtained from earlier paper and particularly of the individual ions [Formula: see text](i), obtained by use of modified TATB assumption reported earlier and also [Formula: see text](i) obtained after correcting for "cavity" effect and Born-type electrostatic effect estimated tentatively by the scaled particle theory (SPT) and simple Bom equation, respectively, reveal the relative order of stabilisation of Cl−, Br−, and I− ions. Analysis of [Formula: see text]–composition profile (X = Cl, Br, and I) exhibits a characteristic "maxima" around 1.5 m NaNO3 with the relative order HI > HBr > HCl in the region of maxima. Moreover, dissection of [Formula: see text] values into the individual ion contributions by use of the modified TATB assumption reported earlier, results in the characteristic "maxima" around 1.5 m NaNO3 in [Formula: see text] or [Formula: see text]–composition profiles for H+ and "minima" for Cl−, Br−, and I−. The results are discussed in terms of ion–ion–solvent interactions as well as the structural changes of the solvents.

Thermodynamics of transfer of glycine, diglycine, and triglycine from water to aqueous solutions of urea, glycerol, and sodium nitrate

1988 ◽  
Vol 66 (3) ◽  
pp. 461-468 ◽  
Author(s):  
Himansu Talukdar ◽  
Sibaprasad Rudra ◽  
Kiron K. Kundu
Keyword(s):  
Sodium Nitrate ◽  
Regular Function ◽  
Scaled Particle Theory ◽  
Aqueous Mixtures ◽  
Free Energies ◽  
Thermodynamics Of Transfer ◽  
Different Temperatures ◽  
Composition Profiles ◽  
Cavity Effect ◽  
Nitrate Solutions

Standard free energies [Formula: see text] and entropies [Formula: see text] of transfer of glycine (G), diglycine (DG), and triglycine (TG), from water to aqueous mixtures of glycerol (GL) and urea (UH) have been determined from solubility measurements at different temperatures. This was also extended to an ionic cosolvent system like aqueous sodium nitrate solutions for G and DG. The observed [Formula: see text] and [Formula: see text]–composition profiles, as well as those obtained after correcting for the "cavity effect" as estimated by scaled particle theory (SPT), were examined in the light of various interactions. The corrected [Formula: see text]and [Formula: see text] values show a regular function of the peptide chain length of the amino acids and impart useful information regarding the involved relative structural effects of these ionic and non-ionic cosolvents.

Transfer free energies of alkali metal chlorides and of some individual ions in glycerol and water mixtures

1980 ◽  
Vol 58 (1) ◽  
pp. 79-85 ◽  
Author(s):  
Indra N. Basumullick ◽  
Kiron K. Kundu
Keyword(s):  
Alkali Metal ◽  
Aqueous Mixtures ◽  
Free Energies ◽  
Dispersion Interactions ◽  
Native Conformation ◽  
Alkali Metal Chlorides ◽  
Metal Chlorides ◽  
Emf Measurements ◽  
Reference Electrolyte ◽  
Electrolyte Ph

Staqndard free energies of transfer, ΔGt0, of alkali metal chlorides from water to aqueous mixtures of 10, 30, 50, and 70 wt.% glycerol have been determined from emf measurements of the double cell comprising Ag– AgCl and K(Hg) electrodes at 25°C. These values were divided into individual ion contributions by use of tetraphenyl arsonium tetraphenyl boride (Ph4AsBPh4) assumption, the required ΔGt0 values of the reference electrolyte (Ph4AsPh4B), obtained by measuring solubilities of KBPh4, Ph4AsPi, and KPi (Pi = picrate) in the solvents. The solvation behaviour of the involved ions, as dictated by their respective ΔGt0(i) values, in this as well as in systems of other similar co-solvents like ethanol, ethylene glycol, and urea, suggests that it is determined by one or several effects of acid-base, Born-type, and dispersion interactions. Moreover, comparable stability of PH4B–, particularly in aqueous glycerol and urea, suggests that "specific interactions" are possibly responsible for the well_known folding-unfolding phenomenon of native conformation of proteins in presence of co-solvents.

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