Thermodynamic study of solvent extraction of monovalent metal picrates with benzo-18-crown-6 into chloroform

Thermodynamic parameters (H _ex ⁰ and S _ex ⁰ ) for the overall extractions of monovalent metal (Na, K, Rb, and Tl) picrates with benzo-18-crown-6 (B18C6), and those (H _D,L ⁰ and S _D,L ⁰ ) for the distribution of B18C6 were determined between chloroform and water. All the extracted B18C6 complexes were l:1:1 complexes (B18C6:metal ion: picrate anion). The H _ex ⁰ and S _ex ⁰ values for all the metals are negative. Every extraction of the metal picrate with B18C6 is completely enthalpy driven. The H _D,L ⁰ and S _D,L ⁰ values of B18C6 are both positive, and the partition of B18C6 is entirely entropy driven. Enthalpy (H _ex,ip ⁰ ) and entropy changes (S _ex,ip ⁰ ) for ion-pair extractions of B18C6-metal ion complexes with picrate anions were calculated. All the H _ex,ip ⁰ and S _ex,ip ⁰ values are negative, and the ion-pair extractions are completely enthalpy driven.     

Square Wave Voltammetric-Thermodynamic Study of the Interaction Between Heavy Metal Ions and Some Macrocyclic Ligands in Water*

The interaction between Cd²⁺ and Pb²⁺ ions and 18-crown-6 (18C6), 1,10-diaza-18-crown-6 (C22) and 1,7-diaza-15-crown-5 (C21) were studied in water solvent at 25, 35, 45 and 55° using square wave voltammetric technique. The stoichiometry and stability of the complexes were determined by monitoring the shift in half-wave or peak potential of the polarographic waves of metal against the ligand concentration. Thermodynamic parameters such as G, H and S were obtained by using a polarographic double wall cell in which the temperature could be fixed to ±0.1°C. The results of all experiments show 1 : 1 complexes, but in addition to 1 : 1 ratio, a 2 : 1 ratio of ligand to cation is also obtained for C22–Pb²⁺ complex. The selectivity order for 18C6 and C22 is Pb²⁺ > Cd²⁺. The thermodynamic data G, H and S values show that the complexes are stabilized by both the enthalpy and entropy terms, but C22–Pb²⁺ complex is stabilized by only enthalpy term.     

Thermochemistry of Complexation of 15-Crown-5 and 18-Crown-6 with Na+and NH+4Ions in Aqueous Solutions

The complexation constants and the heats of complexation of 15-crown-5 (15C5) and 18-crown-6 (18C6) with sodium and ammonium ions in aqueous solutions at several temperatures were determined using calorimetry methods. Thermodynamic characteristics (H°, G°, S°, and C _p°) of the formation of Na(15C5)⁺, Na(18C6)⁺, and NH₄(18C6)⁺were calculated.     

Conductance of iron(III) laurate solutions in binary liquid mixtures

Summary The specific conductivity of iron(III) laurate solutions in binary liquid mixtures shows that the soap aggregates into micelles and CMC is found to be independent of temperature and concentration of benzene, acetone and tetrachloromethane in 1-butanol. The variation of molecular conductance,, with soap concentration, C, is expressed by the equation: = 10^AC^B. Both constants A and B vary with solvent composition but B remains constant with increase in temperature. Several parameters such as molecular conductance at infinite dilution, , dissociation constant, K, heat of dissociation, H, entropy, S and free energy, G of dissociation of soap have been evaluated and the effect of the nature of solvents has been discussed.     

Thermodynamics of protonation of AMP,ADP, and ATP from 50 to 125°C

The interaction of adenosine 5-monophosphate (AMP), adenosine 5-diphosphate (ADP), and adenosine 5-triphosphate (ATP) ions with protons in aqueous solution has been studied calorimetrically from 50 to 125°C and 1.52 MPa. At each temperature, the reaction of acidic AMP with tetramethylammonium hydroxide was combined with the heat of ionization for water to obtain the enthalpy of protonation of AMP, while the reactions of HCl with deprotonated tetramethylammonium salts of ADP and ATP were used to obtain the enthalpies of protonation of ADP and ATP. Equilibrium constant K, enthalpy change H^o, entropy change S^o, and heat capacity change C _p ^o values were calculated for the stepwise protonation reactions as a function of temperature. The reactions involving the first protonation of AMP, ADP, and ATP and the third protonation of ADP and ATP were endothermic over the temperature range studied, while that involving the second protonation is exothermic for AMP and ADP, but is exothermic below 100°C and endothermic at 125°C in the case of ATP. Consequently, log K values for the first and third protonation reactions (phosphate groups) increase while those for the second protonation reaction (N₁-adenine) decrease in the cases of AMP and ADP and go through a minimum in the case of ATP as temperature increases. The H^o values for all protonation reactions increase with temperature. The magnitude and the trend for the H^o, S^o, and C _p ^o values with temperature are discussed in terms of solvent-solute interactions. The magnitude of the C _p ^o values for the second protonation is consistent with little interaction between the phosphate ion and the protonated N₁ site of the adenine moiety in AMP, but indicates moderate interaction between these groups in ADP, and strong interaction in ATP.     

Thermal and volumetric properties of chloroform + triethylamine mixtures and the ideal associated solution model of complex formation

In the ideal associated solution model, activity coefficients of all species (labelled A, B, and AB here) are taken to be unity at all mole fractions and all temperatures, with several derivative consequences that have not previously been investigated. We have applied this model to an analysis of the thermodynamic properties (vapor pressures, excess volumes, excess enthalpies, partial molar enthalpies of solution, and excess heat capacities) of the chloroform + triethylamine system in terms of K, V, H, and C _p for the equilibrium represented by A+B=AB. It is shown that there is good consistency between the relatively simple chemical ideal associated solution model and all available thermodynamic data except heat capacities, for which the consistency between model and data is less good. Some limitation of the ideal associated solution model are discussed, along with the relationship of this model to hydrogen bonding in the AB complex and to spectroscopic investigations. New thermal (partial molar enthalpies of solution and excess heat capacities) and volumetric data are presented.     

First and second thermodynamic mixing properties of ethylbenzene +n-alkanes: Experimental and theory

Isobaric expansibilities _P and isothermal compressibilities _T have been determined at 25 and 45°C for binary mixtures of ethylbenzene + n-tetradecane and + n-hexadecane and the corresponding excess functions (V ^E /T)_P and (V ^E /P)_T have also been obtained. With these data and supplementary literature values, the following second order mixing properties are also reported at 25°C: _S ^E , (V ^E /P)_T, C_V and (VT). All mixing quantities have been compared with the results obtained at 25°C by using the Prigogine-Flory-Patterson theory of liquid mixtures. The predicted values suggest that the ability of ethylbenzene as a breaker of the pure n-C_n orientations is similar to what we found for toluene and higher than for p-xylene.     

Ionic enthalpies of transfer from water to water-sulfolane mixtures

NaCl, NaBr, NaI, NaClO₄, KCl, KClO₄, NaBPh₄, and Ph₄PBr solution enthalpies were measured in water-sulfolane mixtures at 30°C. Ionic enthalpies of transfer from water to mixed solvents were calculated on the basis of the assumption H _s ^o (BPh ₄ ^– )=H _s ^o (Ph₄P⁺). The variation of the ionic enthalpies of transfer with solvent composition is discussed in terms of ion-solvent interactions and of the effects caused by sulfolane on the structure of water.     

Systematik des Adsorptionsverhaltens homologer aliphatischer Amine an der Grenzfläche Quecksilber/Elektrolyt

Zusammenfassung Dutch die wechselstrompolarographische Kapazitäts-Potential-und Kapazitäts-Zeit-Messungen (E _m = konstant) als Funktion der Aminkonzentration wurden die Adsorptionsisothermen homologer Amine und Amin-Hydrochloride beiT = 25 °C undT = 50 °C experimentell bestimmt.Die Ads orptionsisothermen wurden mittels dimensionsloser Adsorptionstherme nachFrumkin-Damaskin ausgewertet und in Form folgender Adsorptionsparameter diskutiert und verglichen: Attraktionskonstantea; Adsorptionskoeffizientb und freie StandardadsorptionsenthalpieG _A .Der Zuwachs in denG _A -Werten pro CH₂-Gruppe läßt sich zuG _A /CH₂0,3–0,5 kcal. Mol^–1 abschätzen. Bis auf wenige Ausnahmen sind die Adsorptionsparametera, b, undG _A Temperaturfunktionen

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Summary The adsorption isotherms of homologous amines and some of their hydrochlorides were obtained from capacity-potential- und capacity-time measurements atT = 25 °C andT = 50 °C.From the adsorption isotherms we computed the thermodynamic adsorption parameters according toFrumkin andDamaskin. On the basis of the adsorption parameters attraction constant (a), adsorption coefficient (b) and free standard energy of adsorptionG _A , the results have been discussed und compared.The increase ofG _A per CH₂-group is aboutG _A /CH₂ 0,3 to 0,5 Kcal Mol^–1. In most cases the adsorption parametersa, b andG _A are temperature functions.

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Mit 3 Abbildungen und 1 Tabelle     

About the adequacy of reference materials

Summary Any analytical procedure includes at least six steps: (1) the sampling; (2) the conditioning of the sample after sampling and its transport to the analytical laboratory; (3) the treatment of the sample at the laboratory; (4) the introduction of the sample into the measurement system; (5) the measurement itself; (6) the processing of the analytical signal and its results. We propose to measure the adequacy of an RM by the factor =^x/^RM, where ^x and ^RM are the errors associated with the analysis of a sample (x) and the RM, respectively. A factor _i can be defined for each step i of the analytical process. The paper examines the means of estimating the parameters _i ^x , _i ^RM and _i for each step of the analytical process. All _i ^x terms excluding those related to the sample treatment and to the measurement can be measured without the use of an RM. To determine the error to be expected from the sample preparation and the measurement it is sufficient to use am RM which is taylored to these two steps only, rather than to the entire analytical process. This may be done for example by spiking a sample with an RM providing the necessary analytical signal. Such RMs are simple and inexpensive to prepare and have very broad applications.     

Synthesis of furan analogs of 1, 3, 5-triphenylpyrazoline derivatives

Furan analogs of chalcones are condensed with phenylhydrazine to give a number of ²-pyrazolines hitherto not described in the literature. It is shown that in , -unsaturated ketones, a nitro-group in the nucleus and remote from the carbonyl group makes cyclization to the corresponding ²-pyrazolines more difficult than does one adjacent to the carbonyl.     

Strain Energies of α-Alkylsubstituted Styrenes, 1,1-Di-phenyl-ethene,Tri-, and Tetra-phenyl-ethene

The standard (p° = 0.1 MPa) molar enthalpies of formation _fH°_m (1 or cr) at the temperature T = 298.15 K were determined by using combustion calorimetry for -ethyl-styrene (A), -iso-propyl-styrene (B), -tert-butyl-styrene (C), 1,1-di-phenyl-ethene (D), tri-phenyl-ethene (E), and tetra-phenyl-ethene (F). The standard molar enthalpies of vaporization _l ^g H°_m or sublimation _cr ^g H°_m of compounds A to F were obtained from the temperature variation of the vapor pressure measured in a flow system. Molar enthalpies of fusion _cr ^l H°_m of solid compounds were measured by d.s.c. Resulting values of _fH°_m (g) were obtained at the temperature T = 298.15 K and used to derive strain enthalpies of phenylalkenes. The interactions of the substituents are discussed in terms of deviations of _fH°_m (g)from the group additivity rules. These values provide a further improvement on the group-contribution methodology for estimation of the thermodynamic properties of organic compounds.     

Kinetics and mechanism of monomolecular heterolysis of commercial organohalogen compounds: XXXVIII. Correlation analysis of solvent effects on the activation parameters of heterolysis of <Emphasis Type="Italic">t</Emphasis>-BuBr and <Emphasis Type="Italic">t</Emphasis>-BuI

Heterolysis of t-BuBr and t-BuI in aprotic solvents involves a H - S compensation effect. The G of t-BuBr heterolysis in aprotic solvents decreases with increasing solvent polarity and cohesion, whereas the respective value for t-BuI heterolysis decreases with increasing solvent polarity, nucleophilicity, and polarizability. In protic solvents, a negative effect of nucleophilic solvation is observed.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 9, 2004, pp. 1476–1483.Original Russian Text Copyright © 2004 by Ponomarev, Zaliznyi, Dvorko.This revised version was published online in April 2005 with a corrected cover date.     

Kinetics and mechanism of the interaction of azide with [(H2O)(tap)2RuORu(tap)2-(H2O)]2+ ion at physiological pH

The title reaction has been studied spectrophotometrically in aqueous medium as a function of [substrate complex], [ligand], pH and temperature at constant ionic strength. At the physiological pH (7.4) the interaction with azide shows two distinct consecutive steps, i.e., it shows a non-linear dependence on the concentration of N₃ ^–; both processes are [ligand]-dependent. The rate constant for the processes are: k ₁10^–3 s^–1 and k ₂10^–5 s^–1. The activation parameters calculated from Eyring plots are: H ₁ = 14.8 ± 1 kJ mol^–1, S ₁ = –240 ± 3 J K^–1 mol^–1, H ₂ = 44.0 ± 1.5 kJ mol^–1 and S ₂ = –190 ± 4 J K^–1 mol^–1. Based on the kinetic and activation parameters an associative interchange mechanism is proposed for the interaction process. From the temperature dependence of the outersphere association equilibrium constant, the thermodynamic parameters calculated are: H ₁ ⁰ = 4.4 ± 0.9 kJ mol^–1, S ₁ ⁰ = 64 ± 3 J K^–1 mol^–1 and H ₂ ⁰ = 14.2 ± 2.9 kJ mol^–1, S ₂ ⁰ = 90 ± 9 J K^–1 mol^–1, which gives a negative G ⁰ value at all temperatures studied, supporting the spontaneous formation of an outersphere association complex.     

Spin conversion of positronium in paramagnetic solutions studied by age-momentum-correlation method

Correlated measurement of the lifetime and of the lineshape of the 511 keV annihilation radiation of positrons (age-momentum correlation, AMOC) has become a powerful tool for investigating reactions of positron or positronium in condensed matter as a function of time. The beam-based ⁺ AMOC method installed at the Stuttgart relativistic positron beam facility (E _kin ^e+ 4MeV) offers substantial advantages over the conventional E coincidence technique resulting in a fast data taking due to the unity detection efficiency of the ⁺ scintillator which provides the start signal for the lifetime measurement. In this paper the application of AMOC to positronium chemistry is illustrated by the study of spin conversion of positronium in the system methanol/HTEMPO as a function of HTEMPO (4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl, a paramagnetic solute) concentration. The same technique can be applied to other systems and other reactions in positronium chemistry, e. g., oxidation or complex formation.     

Kinetics and mechanism of Os(VIII) catalyzed oxidation of dimethyl sulfoxide by vanadium(V)

The title reaction is first order each in vanadium(V) and Os(VIII) and fractional order with respect to DMSO. The rate is found to decrease with increasing concentrations of sulfuric, perchloric and acetic acid, whereas the rate increases with the increasing concentrations of sodium bisulfate and sodium perchlorate. Thermodynamic parameters like E_a, H, S and G were evaluated. A suitable mechanism consistent with the observed kinetics is proposed.     

Effect of acrylamide concentration on the kinetics of oxidation of tartaric acid by cerium(IV) in sulfuric-perchloric acid media

The kinetics of oxidation of tartaric acid by Ce(IV) in the absence and presence of acrylamide has been investigated spectrophotometrically in aqueous H₂SO₄–HClO₄ media at a constant ionic strength 2.0M and 25°C. Oxidation of tartaric acid in both cases was first order with respect to Ce(IV). Kinetic data showed that the reaction involves the formation of an unstable complex and an intermediate free radical. The activation parameters were calculated to be E _a =91.3±0.4 kJ-mol^–1, S=20.2±1.0 J-mol^–1-K^–1, H=88.8±0.4 kJ-mol^–1. A polymerization mechanism is discussed.     

Derivatographische Untersuchung von Verbindungen mit Sterangerüst

Zusammenfassung Die Pyrolyse von ^1,4-Androstadien-3,17-dion und von ^1,4,6-Androstatrien wurde untersucht, dabei die Abspaltungstemperatur des Methans bestimmt und die thermischen Eigenschaften der Pyrolyseprodukte (Östron, 1-Hydroxy-4-methyl-3-desoxyöstron, ⁶-Dehydroöstron und 1-Methyl-⁶-dehydroöstron) geprüft. Eine bisher unbekannte polymorphe Modifikation des Östrons wurde entdeckt. Die polymorphen Modifikationen und das Lösungsmittel-Solvat von 17--Äthinyl-östrodiol wurde ebenfalls untersucht.

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Summary The pyrolysis of 1,4-androstadiene-3,17-dione and of 1,4,6-androstatriene was investigated, the splitting-off temperature of methane was determined, and the thermal properties of the pyrolysis products (estrone, 1-hydroxy-4-methyl-3-desoxyestrone, 6-dehydroestrone and 1-methyl-6-dehydroestrone) were studied. The polymorphic modifications and the solvent-solvate of 17--ethinylestronediol were likewise studied.

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Résumé On a étudié la pyrolyse de la ^1,4-androstadiènedione-3,17 et du ^1,4,6-androstatriène, ce qui a permis de déterminer la température de dissociation du méthane et les propriétés thermiques des produits de pyrolyse (oestrone, hydroxy-1 méthyl-4 désoxy-3 oestrone, déhydro-6 oestrone et méthyl-1 ⁶ déhydrooestrone). On a découvert une modification polymorphe de l'oestrone, inconnue jusqu'à maintenant. On a étudié de plus, les modifications polymorphes et le solvat du dissolvant de l'éthinyl-oestronediol-17-.

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Vorgetragen beim Symposium für analytische Chemie in Graz, 29. September bis 1. Oktober 1965.

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Chinoin Arzneimittelfabrik.     

Ring-Ring Tautomerism in the Series of Isoxazolidine and Δ2-Isoxazoline Derivatives

We have studied the reaction of 5-hydroxy-3,3,5-trimethylisoxazolidine and 5-hydroxy-3,5-dimethyl-²-isoxazoline with derivatives of thiosemicarbazide and also thiocarbonohydrazine. Both reactions serve as a method for synthesis of the previously unknown 5-thiosemicarbazido(thiocarbonohydrazino)isoxazolidines and -²-isoxazolines. ¹H and ¹³C NMR spectroscopy revealed a tendency of the indicated compounds toward ring-chain and ring-ring tautomeric conversions in solutions involving the 1,2,4-triazolidine, ²-pyrazoline, and 1,2,4,5-tetrazine rings.     

Analysis of the Impedance Frequency Spectrum of a Passive Iron Electrode by Combined Impedance and Photoadmittance Measurements

The frequency spectra of electrochemical impedance Z, photocurrent i, and photopotential E are obtained for a passive Fe electrode in 0.2 M KOH in a frequency range 1.3 to 8300 Hz. The validity of relationship E/i = –Z is proved experimentally. The oxide film impedance Z _F is calculated from the frequency spectrum of E with expression Z _F = –E/g. The generation current g is found from the photocurrent frequency spectrum. The frequency impedance spectrum Z _F/S of the oxide/solution interface is determined with equation Z _F/S = Z – Z _F – R _el, where R _el is the solution resistance.