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.

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.

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.

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.

Ion–ion–solvent interactions in aqueous ionic cosolvent systems. II. Single-ion transfer free energies and entropies using tetraphenylarsonium tetraphenylborate reference electrolyte assumption in aqueous sodium nitrate solvent system

1987 ◽  
Vol 65 (11) ◽  
pp. 2595-2604 ◽  
Author(s):  
Sibaprasad Rudra ◽  
Himansu Talukdar ◽  
Kiron K. Kundu
Keyword(s):  
Solvent System ◽  
Mirror Image ◽  
Scaled Particle Theory ◽  
Free Energies ◽  
Emf Measurements ◽  
Solvent Interactions ◽  
Rational Explanation ◽  
Born Equation ◽  
Cavity Effects ◽  
Reference Electrolyte

Single-ion tranfer free energies [Formula: see text] and entropies [Formula: see text] of some electrolytes from water to 1, 2, and 4m aqueous NaNO3 solvents have been determined at 25 °C using the widely used tetraphenylarsonium tetraphenylborate (Ph4AsBPh4) reference electrolyte assumption, after due modification for this solvent system. The required [Formula: see text] and [Formula: see text] values of Ph4AsPi, KBPh4, KPi, AgPi, PbPi2, Ag2CrO4, and AgCl where Pi = picrate, were determined by measuring solubilities at 15–35 °C of the solutes except AgCl, the values of which were determined from emf measurements. Analysis of [Formula: see text] and [Formula: see text] values of the ions as well as their respective true interaction effects, [Formula: see text] and [Formula: see text] as obtained after correcting for their cavity effects [Formula: see text] and [Formula: see text] estimated by the scaled particle theory (SPT) and Born-type electrostatic effects, [Formula: see text] and [Formula: see text] computed by simple Born equation, reveals that the behaviour of the ions in this ionic cosolvent system is chiefly guided by one or several effects of ion–ion–solvent, Born and cavity forming interactions. Moreover, a rational explanation has been offered to explain the observed mirror-image entropie behaviour of simple cations and anions in light of Kundu etal.'s four-steps transfer process.

Transfer thermodynamics of p-nitroaniline in aqueous solutions of some ionic and non-ionic cosolvents and the structuredness of the solvents

1983 ◽  
Vol 61 (3) ◽  
pp. 625-631 ◽  
Author(s):  
Jayati Datta ◽  
Kiron K. Kundu
Keyword(s):  
Three Dimensional ◽  
Water Structure ◽  
Scaled Particle Theory ◽  
Aqueous Mixtures ◽  
Promoting Effect ◽  
Salting Out ◽  
Aqueous Urea ◽  
Different Temperatures ◽  
Composition Profiles ◽  
Transfer Thermodynamics

Standard free energies [Formula: see text] and entropies [Formula: see text] of transfer of p-nitroaniline (pNA) from water to aqueous mixtures of some ionic and non-ionic cosolvents like KBr, urea (U), propylene glycol (PG), glycerol (GL), dioxane (D), and 1,2-dimethoxyethane (DME) have been determined from solubility measurements at different temperatures. The observed [Formula: see text]–composition profile in KBr solution appears to result from the well known salting-out effect of the salt and those in aqueous poly-ols and ethers are the result of the combined effects of dispersion and "acid–base" type interactions but that in aqueous urea solutions is governed by the "salting-out" type interaction by the predominant zwitterionic form of urea. The observed [Formula: see text]–composition profiles as well as those obtained after correcting for the "cavity-effect", as estimated tentatively by the scaled particle theory (SPT), were examined in the light of Kundu et al.'s semi-quantitative theory proposed earlier. The latter profiles suggest that unlike isopropyl alcohol (IPA), the poly-ols and ethers as well as KBr and urea induce structure breaking of three dimensional (3D) water structure right from the initial compositions. Moreover, the observed "roller-coaster" type behaviour of the profile in aqueous urea is indicative of the effect of urea–water aggregation around 4–10 m urea. Also, the observed graded reduction of structure-promoting effect of IPA in PG and GL cosolvent systems confirms that structuring and destructuring ability of a cosolvent depends on the ratio of hydrophobicity to hydrophilicity of the cosolvent.

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.

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.

Thermodynamics of transfer of p-nitroaniline from water to alcohol + water mixtures at 25 °C and the structure of water in these media

1977 ◽  
Vol 55 (23) ◽  
pp. 3961-3966 ◽  
Author(s):  
Kumardev Bose ◽  
Kiron K. Kundu
Keyword(s):  
Mixed Solvents ◽  
Solvent Structure ◽  
Free Energies ◽  
Solvent Interactions ◽  
Structure Of Water ◽  
Thermodynamics Of Transfer ◽  
Alcohol Water ◽  
Composition Profiles

Free energies (ΔGt0) and entropies (ΔSt0) of transfer at 25 °C of the nonelectrolyte p-nitroaniline from water to various alcohol + water mixtures have been determined from solubility measurements at seven temperatures from 10–40 °C. Increasing specific solute–solvent interactions have been proposed to interpret the nature of the ΔGt0-composition profiles and the enhanced structure of water in the water-rich mixed solvents has been correlated with maxima in the ΔSt0-composition profiles. The effectiveness of p-nitroaniline as a useful probe for studying solvent structure has been pointed out.

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