Transfer free energies of some ions from water to dimethylsulfoxide-water and urea-water mixtures

The standard free energies of transfer (G _t ^o ) of some electrolytes from water to aqueous mixtures of dimethylsulfoxide (DMSO) and of urea have been split into the contribution from individual ions by use of the reference electrolyte Ph ₄ AsBPh ₄ (RE), where Ph=phenyl. For each of the solvents, G _t ^o (Ph ₄ AsBPh ₄ ) was determined from the solubility products of the salts KBPh ₄ , Ph ₄ AsPi, and KPi, where Pi=picrate ion. The observed G _t ^o (i) values for the individual ions are strikingly different from the corresponding values obtained by the simultaneous extrapolation (SE) procedure reported earlier.     

Solubilities in aqueous mixtures oft-butanol andtrans-dichlorotetra(3-alkylpyridine) cobalt(III) hexachlororhenate(IV): Gibbs energies of transfer of the complex cations

The solubilities of the hexachlororhenate(IV) salts of the complex cations trans-[Co(3Mepy)₄Cl₂]⁺ and trans-[Co(3Etpy)₄Cl₂]⁺ have been determined in water+t-butyl alcohol mixtures. By reference to the solubilities of Cs₂ReCl₆ and the Gibbs energies of transfer of Cs⁺ from water into water+t-butyl alcohol mixtures, G _t ^o (Cs⁺), G _t ^o [Co(3Mepy)₄Cl ₂ ⁺ ] and G _t ^o [Co(3Etpy)₄Cl ₂ ⁺ ] are calculated. These latter values, when introduced into the equation for a free energy cycle applied to the process of the initial state going to the transition state for the solvolyses of these two cations, produces values for G _t ^o [Co(3Mepy)₄Cl^2+*] and G _t ^o [Co(3Etpy)₄Cl^2+*] for the Co³⁺ cations in the transition state. These values are compared with (G _t ^o (i) for i=[Co(Rpy)₄Cl₂]⁺, [Co(Rpy)₄Cl]^2+*, [Coen₂XCl]⁺ and [Coen₂X]^2+* to investigate the influence of the hydrophobicity of the surface of the complex on its stability in the mixtures. G _t ^o (i) (solvent sorting) are compared with G _t ^o (i) (TATB).     

Standard Gibbs energies of transfer of potassium tetraphenylborate from water to straight-chain n-alkanols

Solubilities of potassium tetraphenylborate in water, methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol, 1-hexanol, and 1-octanol at 15, 25, 35, 45, 55°C have been determined by spectrophotometry. The standard Gibbs energy of transfer of potassium tetraphenylborate form water to straightchain n-alkanols and the medium effect of potassium tetraphenylborate from 15 to 55°C have been calculated. Furthermore, the contribution of microscopic interactions to the standard Gibbs energy of transfer of potassium tetraphenylborate is calculated and discussed.     

Standard Gibbs energies of transfer of rubidium tetraphenylborate from water to straight-chain n-alkanols

Solubilities of ribidium tetraphenylborate in water,methanol,ethanol,1-propanol,1-butanol,l-pentanol,1-hexanol and 1-octanol at 288.15,298.15,308.15,318.15,328.15 K have been determined by spectrophotometry.The standard Gibbs energy of transfer of ribidium tetraphenylborate from water to straight-chain n-alkanols and the primary medium effect of rubidium tetraphenylborate from 288.15 to 328.15 K have been calculated.Furthermore,the contribution of microscopic interactions to the standard Gibbs energy of transfer of rubidium tetraphenylborate is calculated and discussed.     

Determining the Gibbs energy of ion transfer across water-organic liquid interfaces with three-phase electrodes.

Ions can be transferred between immiscible liquid phases across a common interface, with the help of a three-electrode potentiostat, when one phase is an organic droplet attached to a solid electrode and containing a redox probe. This novel approach has been used in studies to determine the Gibbs energy of anion and cation transfer, ranging from simple inorganic and organic ions to the ionic forms of drugs and small peptides. This method of studying ion transfer has the following advantages: (1) no base electrolytes are necessary in the organic phase; (2) the aqueous phase contains only the salt to be studied; (3) a three-electrode potentiostat is used; (4) organic solvents such as n-octanol and chiral liquids such as D- and L-2-octanol can be used; (5) the range of accessible Gibbs energies of transfer is wider than in the classic 4-electrode experiments; (6) the volume of the organic phase can be very small, for example, 1 microL or less; (7) the experiments can be performed routinely and fast. Herein, the basic 5 principle is outlined, as well as a summary of the results obtained to date, and a discussion on the theoretical treatments concerning the kinetic regime of the three-phase electrodes with immobilized droplets.     

In(Ⅲ)的标准迁移吉布斯自由能

通过直流极谱法对In(Ⅲ) 从纯水到蔗糖及葡萄糖水溶液的标准迁移吉布斯自由能(GtΘ)进行了研究，根据In(Ⅲ)的可逆半波电位和扩散系数求得GtΘ.实验表明, GtΘ随蔗糖及葡萄糖浓度的增加而逐渐减小,说明In(Ⅲ)在蔗糖及葡萄糖水溶液中的稳定性增加. GtΘ可分为静电能和化学能两部分，化学能逐渐降低表明蔗糖及葡萄糖水溶液比纯水碱性强.根据三元体系中溶质-溶剂和溶质-溶质的相互作用对实验结果进行了讨论.     

Solvent donor and acceptor properties of pyridine

Polarographic and cyclovoltammetric measurements on the perchlorates of Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, Tl⁺, Ba²⁺ and Ni²⁺ as well as on the trifluoromethane sulfonates of Zn²⁺, Cd²⁺, Pb²⁺, Cu²⁺, Cu⁺, Mn²⁺ and Co²⁺ were carried out. The data allowed the evaluation of the different donor behavior of pyridine towards hard, border line and soft cations. The conclusions drawn from electrochemical investigations were supported by Gibbs energies of transfer for cations, which were derived from both electrochemical measurements based on the bis(biphenyl)chromium assumption and from solubility studies based on the tetraphenylarsonium tetraphenylborate assumption. The acceptor properties of pyridine were obtained from the solvatochromic dyes bis(cyano)bis(1,10-phenanthroline)iron(II) and bis(cyano)bis(3,4,7,8-tetramethyl-1,10-phenanthroline)iron(II) and the results were compared with the acceptor number and the E _T -value.     

Donor and acceptor properties of the solvents tetrahydrofuran and tetrahydrothiophene

The donor and acceptor properties of tetrahydrofuran and tetrahydro-thiophene were evaluated by means of electrochemical and spectroscopic methods. Polarographic and cyclovoltammetric data for LiClO₄, NaClO₄, KClO₄, RbClO₄, CsClO₄, Ba(ClO₄)₂, AgCF₃SO₃, TlClO₄, Zn(CF₃SO₃)₂, Cd(CF₃SO₃)₂, Cu(CF₃SO₃)₂, Pb(CF₃SO₃)₂, Mn(CF₃SO₃)₂, Co(CF₃SO₃)₂, Ni(ClO₄)₂·2H₂O, oxygen, perylene, ferrocene, and bis(biphenyl)chromium tetraphenylborate in tetrahydrofuran and of TlClO₄, CuCF₃SO₃, Pb(CF₃SO₃)₂, Cd(CF₃SO₃)₂, oxygen, ferrocene and bis(biphenyl)chromium tetraphenylborate in tetrahydrothiophene together with the potentials of the Ag/0.01 M Ag⁺-ion electrodes in these two solvents are given. Molar Gibbs (free) energies for the transfer from acetonitrile into tetrahydrofuran for Na⁺, K⁺, Rb⁺, Ag⁺, Tl⁺, Zn²⁺, Cd²⁺, and Pb²⁺, and for the transfer into tetrahydrothiophene for Ag⁺, Cu⁺, Tl⁺, Cd²⁺, and Pb²⁺ were calculated from these data. Visible spectra were obtained for the solvatochromic dyes acetylacetonato(N,N,N,N,-tetramethylethylenediamine) copper(II) perchlorate and for 2,6-diphenyl-4-(2,4,6-triphenyl-l-pyridinio)phenoxide, which served as secondary standards to obtain donor and acceptor numbers. The changes in half-wave potentials of the cations vs. bis(biphenyl)chromium(I)/(0) and the Gibbs energies of transfer are discussed on basis of hard and soft donor properties of these two solvents.     

Solvent properties of ethanediol and 2-mercaptoethanol

The nature of interactions between solutes and the solvents ethanediol and 2-mercaptoethanol were studied employing polarography, cyclic voltammetry and visible spectroscopy. The polarographic and voltammetric behavior of TlClO₄, Zn(CF₃SO₃)₂, Cd(CFP₃SO₃)₂, Pb(CF₃SO₃)₂, Cu(CF₃SO₃)₂, Mn(CF₃SO₃)₂, Co(CF₃SO₃)₂, Ni(ClO₄)₂·2H₂O, oxygen and bis(biphenyl)-chromium(I) tetraphenylborate or iodide were measured. Gibbs energies of transfer based on the bis(biphenyl)chromium assumption were calculated for the transfer from acetonitrile into ethanediol for Tl⁺, Ag⁺, Cd²⁺, and Pb²⁺ as well as for Tl⁺, Cu⁺, Cd²⁺, and Pb²⁺ into 2-mercaptoethanol. The solvatochromic shift of acetylacetonato (N, N, N, N-tetramethyl-ethylenediamine)copper(II) perchlorate was used to evaluate the hard donor properties of ethanediol. The acceptor properties of both solvents were estimated from the low energy visible absorption band of bis(cyano)bis(1,10-phenanthroline)iron(II). The different behavior of ethanediol and 2-mercaptoethanol is discussed on the basis of the changes of half-wave potentials, of Gibbs energies of transfer and of the shifts of the solvatochromic compounds.     

Ions in Aqueous Acetic Acid Mixtures: Solvent Reorganization around Protons and Gibbs Energies of Transfer from Water

The photo-absorbing, basic sensor, 4-nitroaniline, has been used to determine theequilibrium constant for solvent reorganization around the proton in mixtures ofvarying composition of water with acetic acid. In all the mixtures used, theself-ionization of the acetic acid was suppressed. In contrast to mixtures of waterwith the related ethanol or acetone, this equilibrium is shifted more toward thewater-solvated species as the mole fraction x ₂ of the cosolvent increases. TheGibbs energy of transfer of protons from water into the mixture G ^o _t (H⁺) can bederived with the aid of this equilibrium constant for the solvent reorganization.Using G ^o _t (H⁺), G ^o _t (i) for i denoting anions and other cations can be evaluated.In comparison the G ^o _t (i) for cations have lower negative values than when eitherethanol or acetone is added to water. Correspondingly, for halide anions, thepositive G ^o _t (i) with added acetic acid are rather less than is found with eitherethanol or acetone added. The influence on the ion-solvent interaction of bothelectron withdrawing hydroxy and carbonyl groups in acetic acid may beresponsible for this. Although G ^o _t (i) for C10^– ₄ and Re0^– ₄ are also positive, both picrateions and OH^– give negative values with acetic acid added to water. With picrateions, the hydrophobic effect of the carbon ring produces stabilization in themixture relative to water. With OH^–, complete conversion to acetate anionsoccurs. As is found with other cosolvents, the contribution of the charge onacetate anion to G ^o _t (CH₃COO^–) is found to increase as x ₂ rises. The aciddissociation constant K _a for acetic acid is found to decrease slowly as x ₂ rises to0.5, followed by a rapid decrease for x ₂ greater than 0.7 where dimerization ofacetic acid occurs.     

Gibbs functions for transfer of divalent metal cations from water to water + methanol mixtures using potentiometry, polarography and solubility measurements

Gibbs functions for transfer from water to methanol and to a full range of water + methanol mixtures were obtained for Cu²⁺, Cd²⁺, Pb²⁺, Hg²⁺, Zn²⁺, Mg²⁺, Ca²⁺, Sr²⁺ and Ba²⁺ using potentiometric or polarographic measurements in these solvents. In addition, data were obtained from the solubility products of the alkaline-earth iodates. From values obtained by the different methods and literature data, a table of selected values is given.     

Crystal structure of calcium cis(N)-bis(iminodiacetato)chromate(III) nonahydrate Ca[Cr(Ida)2]2·9H2O

In the crystals of [Ca(H₂O)₅][Cr(Ida)₂]₂·4H₂O (triclinic symmetry, a = 10.1056(10) ?, b = 13.0077(11) ?, c = 13.1185(13) ?, α = 70.186(11)°, β = 81.248(11)°, γ = 78.996(11)°, Z = 2, space group P ) cyclic centrosymmetric tetramers are present. In them calcium ions are bonded to oxygen atoms of the carboxyl groups of two octahedral complex cis(N)-[Cr(Ida)₂]⁻ ions (Ida is the iminodiacetic acid anion). The O atoms of five water molecules complete the Ca atom environment to a distorted pentagonal bipyramid. Isolated [Cr(Ida)₂]⁻ ions of a similar structure neutralize the positive charge of tetramers. Original Russian Text Copyright ? 2009 by M. Zabel, V. I. Pavlovskii, and A. L. Poznyak __________ Translated from Zhurnal Strukturnoi Khimii, Vol. 50, No. 3, pp. 602–604, May–June, 2009.     

Structures,stabilities and adiabatic ionization and electron affinity energies of small sulfur clustersS 3-S 5

Summary The vertical and adiabatic ionization and electron affinity energies are calculated for the isomers ofS ₃,S ₄ andS ₅. For the existing isomers the structures of several ionic states were optimized using an RHF analytical gradient approach with a subsequent frequency analysis. The many-body effects were taken into account by Green function (for vertical energies) and CI (for vertical and adiabatic energies) techniques. The structural relaxation upon ionization or attachment of an electron is found to be of primary importance to account for the sequence of cationic states or the existence of a positive electron affinity.Dedicated to Professor W. Kutzelnigg on the occasion of his 60th birthday.     

Systematic regularities of molecular SCF energies

New formulae for the approximate computation of total molecular energies are developed based on ab initio calculations of n-alkanes. Their application to various kinds of molecules reveals that good expectation values for total molecular energies can be obtained by considering only the one-electron terms h _i and the nuclear repulsion energy. It is further shown that very good agreement with SCF total energies is obtained by a relationship which connects the total energy with the sum of inner-shell (core) orbital energies. The results turn out to be better than those obtained using Ruedenberg's approximation, which takes both inner-shell and valence-shell orbital energies into account.     

Gibbs energies of interaction of the CH2 and CHOH groups from freezing point data for aqueous binary mixtures of D-mannitol,myo-inositol,and cyclohexanol

Freezing temperatures of dilute aqueous solutions of D-mannitol, myo-inositol, D-mannitol + myo-inositol, D-mannitol + cyclohexanol, and myo-inositol + cyclohexanol have been measured over the concentration range 0.1 to 1.0 mol-kg^–1. These data yield pairwise molecular Gibbs energies of interaction which have been corrected to 25°C and treated according to the Savage-Wood additivity principle to give pairwise functional group Gibbs energies of interaction for CH₂/CH₂, CH₂/COOH, and CHOH/CHOH. Anomalous behavior of some systems is discussed in terms of the interactions.     

Vibrational spectra and ab initio analysis of tert-butyl, trimethylsilyl, trimethylgermyl, trimethylstannyl, and trimethylplumbyl derivatives of 3,3-dimethylcyclopropene X. Some regularities

The changes in the vibrational frequencies of 1-tert-butyl and 1,2-di-tert-butyl derivatives of 3,3-dimethylcyclopropene brought about by substitution of the central carbon atom (X) of the tert-butyl moieties by Si, Ge, Sn, or Pb atoms are examined. The most important decrease in the vibrational frequencies implicating the X(CH(3))(3) moieties is noted for substitution of X=C by Si. The substitutions of Si by Ge or Ge by Sn or Sn by Pb are not accompanied by the pronounced frequency shifts observed for the C-->Si transition. An explanation is given for trends in these vibrational frequencies for the transitions X=C-->Si-->Ge-->Sn-->Pb. It is concluded that there are lower limiting values of the vibrational frequencies of a molecular moiety which are approached when the mass of its isovalent atom is increased. This leads to the formation of cluster regions in the vibrational spectra for the frequencies of the SnC(3) and PbC(3) moieties.     

High levelab initio stabilization energies of benzene

Summary G2 theory is shown to be reliable for calculating isodesmic and homodesmotic stabilization energies (ISE and HSE, respectively) of benzene. G2 calculations give HSE and ISE values of 92.5 and 269.1 kJ mol^–1 (298 K), respectively. These agree well with the experimental HSE and ISE values of 90.5±7.2 and 268.7±6.3 kJ mol^–1, respectively. We conclude that basis set superposition error corrections to the enthalpies of the homodesmotic or isodesmic reactions are not necessary in calculations of the stabilization energies of benzene using G2 theory. The calculated values of the enthalpies of formation of such molecules containing multiple bonds such as benzene ands-trans 1,3-butadiene, which are found from the enthalpies of isodesmic and homodesmotic reactions rather than of atomization reactions, demonstrate good performance of G2 theory. Estimates of theH _f ^o value for benzene from the G2 calculated enthalpies of homodesmotic reaction (2) and isodesmic reaction (3) are 80.9 and 82.5 kJ mol^–1 (298 K), respectively. These are very close to the experimentalH _f ^o value of 82.9±0.3 kJ mol^–1. TheH _f ^o value ofs-trans 1,3-butadiene calculated using the G2 enthalpy of isodesmic reaction (4) is 110.5 kJ mol^–1 and is in excellent agreement with the experimentalH _f ^o value of 110.0±1.1 kJ mol^–1.     

Kinetics and mechanism of oxidation of S2O 32? by potassium bis (tellurato) cuprate(III)

The kinetics of oxidation of sodium thiosulphate by potassiumbis(tellurato) cuprate(III) in an alkaline medium has been reported. The reaction is first order in [S₂O ₃ ²⁻ ] but zero order in copper(III). Hydroxide ions are found to retard the oxidation rate. A rate expression rationalising the kinetic data has been derived. Sodium tetrathionate has been found to be the product of oxidation.     

Synthesis and stereochemical nonrigidity of isomeric Zn(ii)bis-[N-isopropyloxy(mercapto)naphthaldiminates]

Kinetics and reaction mechanisms governing inversion of the tetrahedral configuration at the metal center in the series ofbis-chelate Zn(II) complexes of 3,2-, 1,2-, and 2,1-oxy(mercapto)naphthaldimines, respectively4–6, have been studied with the use of dynamic¹H NMR spectroscopy. A polytopal rearrangement of the diagonal twist type has been found to be an energetically preferable pathway of the inversion reaction for complexes4 and5 with a ZnN₂O₂ coordination site, whereas the inversion reaction for complexes with a ZnN₂S₂ coordination site occurs by an intramolecular dissociation-recombination pathway that involves cleavage of a Zn-N coordination bond. In the case of complexes6, the inversion reaction is governed mainly by intramolecular degenerate ligand exchange reactions.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11. pp. 2261–2265, November, 1995.This work was supported by the Russian Foundation for Basic Research (project No. 93-03-18692) and the International Science Foundation (grant No. RNJ 000).     

Thermodynamic parameters for the transfer of ions from water to propylene carbonate

There are large discrepancies between various recorded values for the free energy of transfer of the alkali metal cations from water to propylene carbonate. Using the known enthalpies of transfer given byKrishnan andfriedman, and the entropy correlation introduced byAbraham, these discrepancies are resolved in favour of the values obtained byCourtot-Coupez et al. and those due (indirectly) toGritzner. This enables, for the first time, a reasonably reliable set of free energies, entropies, and enthalpies of transfer to be constructed.

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Thermodynamische Parameter für die Übertragung von Ionen von Wasser in Propylencarbonat

Zusammenfassung Die verschiedenen veröffentlichten Werte für die freie Enthalpie der Übertragung von Alkalimetallkationen von Wasser in Propylencarbonat zeigen große Unstimmingkeiten. Diese Unstimmigkeiten können zugunsten der Werte vonCourtot-Coupez et al. und der (indirekten) vonGritzner behoben werden, wenn man die bekannten Werte für die Übertragungsenthalpie vonKrishnan undFriedman, und die vonAbraham eingeführte Entropiekorrelation benützt. Es ist nun zum ersten Mal möglich, relativ zuverlässige Werte für die freie Energie, Entropie und Enthalpie auszuarbeiten.