Effect of charge on the standard partial molar volumes and heat capacities of organic electrolytes in methanol and water

Previously developed additivity schemes for nonelectrolytes have been used to estimate and for tetraalkyl and tetraphenyl methanes in methanol and water. Corrections have been applied to the thermodynamic values of these model compounds to account for a variation in size of the central atom, and these were used to ascertain the effect of charge on and of alkyl and phenyl quaternary ions having N, P and B as central atoms. Investigations of R₄NBr, (R=methyl to heptyl) salts show that the charge effect on and of R₄N⁺ ions is large and relatively independent of ion size suggesting that the solvent molecules penetrate the ions. The ability to estimate and of the quaternary ions in the bromide salt solutions has made it possible to make ionic assignments with some confidence; (Br^–) has been evaluated as 19.7±2 and 30.2±7 cm³-mol^–1 and (Br^–) as –83±7 and –68±30 J-K^–1-mol^–1 in methanol and water, respectively. The use of organic ions for making ionic assignments of and is critically examined and comparisons with other assignments are made. The scaled particle theory is employed to divide the heat capacities of electrolytes into cavity and interaction contributions.     

First and second thermodynamic mixing functions of ethylbenzene+n-nonane, +n-decane,and+n-dodecane at 25 and 45°C

Isothermal compressibilities _T and isobaric thermal expansion coefficients _p have been determined for mixtures of ethylbenzene+n-nonane, +n-decane, and +n-dodecane at 25 and 45°C in the whole range of composition. The excess functions and have been obtained at each measured mole fraction. The first one is zero for ethylbenzene +n-nonane, positive for ethylbenzene +n-decane, and +n-dodecane and increases with chain length n of the n-alkane. The function is positive for the three studied systems and nearly constant with n. Both mixing functions increase slightly with temperature. From this measurement and supplementary literature data of molar heat capacities at constant pressure C _P , the isentropic compressibilities _S, the molar heat capacities at constant volume C _V and the corresponding mixing functions have been calculated at 25°C. Furthermore, the pressure dependence of excess enthalpy H ^B , at zero pressure and at 25°C has been obtained from our experimental results of and experimental literature values for excess volume V ^E .     

Thermodynamic Properties of Aqueous Dimethylamine and Dimethylammonium Chloride at Temperatures from 283 K to 523 K: Apparent Molar Volumes, Heat Capacities, and Temperature Dependence of Ionization

Data for the apparent molar volumes of aqueous dimethylamine and dimethylammonium chloride have been determined with platinum vibrating tube densimeters at temperatures 283.15 K T 523.15 K and at different pressures. Apparent molar heat capacities were measured with a Picker flow microcalorimeter over the temperature range 283.15 K T 343.15 K at 1 bar. At high temperatures and steam saturation pressures, the standard partial molar volumes of dimethylamine and dimethylammonium chloride deviate towards positive and negative discontinuities at the critical temperature and pressure, as is typical for many neutral and ionic species. The revised Helgeson-Kirkham-Flowers (HKF) model and fitting equations based on the appropriate derivatives of solvent density have been used to represent the temperature and pressure dependence of the standard partial molar properties. The standard partial molar heat capacities of dimethylamine ionization , calculated from both models, are consistent with literature data obtained by calorimetric measurements at T 398 K to within experimental error. At temperatures below 523 K, the standard partial molar volumes of dimethylamine ionization agree with those of morpholine to within 12 cm³-mol^-1, suggesting that the ionization of secondary amine groups in each molecule is very similar. The extrapolated value for of dimethylamine above 523 K is very different from the values measured for morpholine at higher temperature. The difference is undoubtedly due to the lower critical temperature and pressure of (CH₃)₂NH(aq).     

Effect of solvent on the partial molal volumes and heat capacities of nonelectrolytes

Group contributions to in seven solvents and to in three solvents have been tabulated. The variation of group parameters is discussed in terms of the solvent compressibility coefficient, _T. The scaled particle theory (SPT) is used to calculate cavity contributions to and C _p2 ^o . Interaction contributions are obtained from the cavity terms and and values estimated through the additivity schemes. values are more sensitive to solute-solvent interactions than in water and less sensitive in methanol. The SPT results for heat capacities support the concept of structural promotion by hydrophobic solutes in water.     

Modeling of Thermodynamic Properties of Amino Acids and Peptides Using Additivity and HKF Theory

Relative densities, , and heat capacity ratios, of aqueous L-histidine, L-phenylalanine, L-tyrosine, L-tryptophan, and L-2,3-dihydroxyphenylalanine (L-dopa) have been measured at 15, 25, 40, and 55°C and 0.1 MPa. Apparent molar volumes, V _2,, apparent molar heat capacities, C_P2,, partial molar volumes at infinite dilution, , and partial molar heat capacities at infinite dilution, , have been calculated from these measurements and compared to available literature values. The partial molar properties at infinite dilution for these systems have been added to those previously obtained for amino acids and peptides in water and the combined set used as input to a novel additivity analysis. The model we develop is based upon the equations of state of Helgeson, Kirkham, and Flowers (HKF) and has been constructed with additive parameters. The model may be used to predict thermodynamic properties of many aqueous biochemicals over an extended temperature range. Group contributions to the parameters in our model and effective Born coefficients are reported for 24 aqueous amino acid and peptide systems. Our results are compared to data previously published in the literature.     

Heat capacity changes for the lonization of aqueous phenols at 25°C

The apparent molal heat capacities have been determined at 25°C for phenol,meta-nitrophenol,para-nitrophenol,meta-cyanophenol, andpara-cyanophenol and the corresponding sodium salts in water at several concentrations. These values have been extrapolated to infinite dilution to provide the values from which the heat capacity changes for the ionization of the aqueous phenols have been calculated. The observed values are virtually identical within experimental error for the phenols studied. The volume data needed to calculate the values from the experimental data are also reported.To whom correspondence should be addressed.     

Volumetric Properties of Binary Mixtures of Acetonitrile and Chloroalkanes at 25°C and Atmospheric Pressure

Excess molar volumes for binary mixtures of acetonitrile + dichloromethane, acetonitrile + trichloromethane, and acetonitrile + tetracloromethane at 25°C have been used to calculate partial molar volumes , excess partial molar volumes , and apparent molar volumes of each component as a function of composition. The V _m ^Evalues are negative over the entire composition range for the systems studied. The applicability of the Prigogine–Flory–Patterson theory was explored. The agreement between theoretical and experimental results is satisfactory for the systems with dichloromethane and tetrachloromethane. For the unsymmetrical behavior of the system with trichloromethane, however, the agreement is poor.     

Partial molal heat capacities of aqueous tetraalkylammonium bromides as functions of temperature

Enthalpies of solution have been measured from 5 to 85°C for aqueous tetraethyl- and tetrapropylammonium bromides, and the integral heat method is employed to evaluate for these electrolytes over a wide temperature range. Data taken from the literature have been used to evaluate for aqueous Bu₄NBr over a similar temperature range. These data, along with similar data for Me₄NBr, previously reported, have been used to evaluate absolute ionic heat capacities. While the absolute values agree only qualitatively with two other methods of division, the temperature dependences of the three methods essentially agree up to 65°C. Heat capacities due to structural effects on the solvent, obtained by subtracting the inherent heat capacities of the ions, are extraordinarily positive for all four tetraalkylammonium ions and have negative temperature coefficients, indicating that all four ions, including the tetramethylammonium ion, are structure-making ions.     

Group additivity for the standard partial molal heat capacities and volumes of polar compounds in methanol at 25°C

A flow heat capcity calorimeter and a flow vibrating tube densimeter have been used to measure the apparent molal heat capacities and volumes of benzene and 25 polar compounds in methanol at 25°C. These quantities have been extrapolated to infinite dilution to obtain the standard partial molal heat capacities and volumes. The and data have been used in conjunction with an additivity scheme previously determined for alkanes. Group contributions were evaluatd for –OH, –NH₂, –COOH, –C₆H₅, C=O, –COO–, –CONH–, –O–, –S–, and –S₂–. The concentration dependences of _cp and _v of nonelectrolytes in methanol are qualitatively similar but much smaller than in water.     

Solubility of Oxygen in Some 1-1, 2-1, 1-2, and 2-2 Electrolytes as a Function of Concentration at 25°C

The solubility of oxygen has been measured in a number of electrolytes [(LiCl, KCl, RbCl, CsCl, NaF, NaBr, NaI, NaNO₃, KBr, KI, KNO₃, CaCl₂, SrCl₂, BaCl₂, Li₂SO₄, K₂SO₄, Mn(NO₃)₃)] as a function of concentration at 25°C. The solubilities, mol (kg-H₂O)^–1, have been fitted to a function of the molality m (standard deviation < 3mol-kg^–1)

Partial molar heat capacities of selected electrolytes and benzene in methanol and dimethylsulfoxide at 25, 40, and 80°C

A high temperature-high pressure flow heat capacity calorimeter, designed to operate to 350°C and 20 Mpa, has been constructed and tested with aqueous sodium chloride solutions to 80°C. The calorimeter has been used to measure the specific heats for solutions of NaBr, NaClO₄, ₄PBR, NaB₄, and benzene in methanol (MeOH) and dimethylsulfoxide (DMSO) at 40 and 80°C. A commercial calorimeter was used to measure the same systems at 25°C. Apparent molar heat capacities C>_p, have been evaluated and extrapolated to infinite dilution to obtain standard partial molar heat capacities . For electrolytes are positive and insensitive to temperature to 80°C in DMSO, but in MeOH, C _{p, 2} ⁰ for simple electrolytes are negative and become increasingly negative with temperature. The behavior in MeOH is attributed to strong electrostriction by ionic charge and solvation of anions by MeOH molecules which increases with temperature. This is similar to observed behavior of electrolytes in water above 100°C. For benzene is positive in MeOH and DMSO, and increases with temperature.     

Excess partial molar volumes and thermal expansivities in the water-rich region of aqueous 2-butanone

Excess partial molar volumes of 2-butanone V _m ^E (B) and thermal expansivities _p were measured in the water-rich region of aqueous 2-butanone. The composition derivatives of both quantities showed anomalies at about X _B =0.033 (x _B is the mole fraction of B). showed a step anomaly, while exhibited a peak anomaly. The compositions at which these anomalies occurred match those of the step anomalies observed earlier in and in aqueous 2-butanone. These results are discussed in comparison with those obtained previously for aqueous 2-butoxyethanol.Presented at the Symposium, 76^th CSC Congress, Sherbrooke, Quebec, May 30–June 3, 1993, honoring Professor Donald Patterson on the occasion of his 65^th birthday.     

Partial molar heat capacities and volumes of transfer of nucleic acid bases,nucleosides and nucleotides from water to aqueous solutions of sodium and calcium chloride at 25°C

Partial molar heat capacities and volumes of some nucleic acid bases, nucleosides and nucleotides have been measured in 1m aqueous NaCl and CaCl₂ solutions using Picker flow microcalorimeter and a vibrating tube digital densimeter. The partial molar heat capacities of transfer and volumes of transfer from water to the electrolyte solutions were calculated using earlier data for these compounds in water. The values of these transfer parameters are positive. The higher values for transfer to aqueous CaCl₂ solutions reflect the stronger interactions of the constituents of the nucleic acids with Ca⁺² ions than with the Na⁺ ions.     

Reaction graphs and a construction of reaction networks

Summary A general definition of reaction graphs is presented. For a pair of isomeric molecular graphs and , related by a chemical transformation , the reaction graph is determined using a maximal common subgraph defined for vertex mapping . A binary operation defined for graphs constructed over the same vertex set enables us to decompose the reaction graph into the sum of prototype reaction graphs. A decomposition of an overall reaction graph can be advantageously used for the construction of a reaction network. An oriented path in this network beginning at and ending at corresponds to a breakdown of the transformation into a sequence of intermediates.     

Comprehensive Investigation of Yttrium and Rare Earth Element Complexation by Carbonate Ions Using ICP–Mass Spectrometry

Carbonate stability constants for yttrium and all rare earth elements have been determined at 25°C and 0.70 molal ionic strength by solvent exchange and inductively coupled plasma–mass spectrometry (ICP–MS). Measured stability constants for the formation of and from M³⁺ are in good agreement with previous direct measurements, which involved the use of radio-chemical techniques and trivalent ions of Y, Ce, Eu, Gd, Tb, and Yb. Direct ICP–MS measurements of and formation constants are also in general agreement with modeled stability constants for the metals La, Pr, Nd, Sm, Dy, Ho, Er, Tm, and Lu, based on linear-free energy relationship (LFER). The experimental procedures developed in this work can be used for assessing the complexation behavior of other geochemically important ligands such as phosphate, sulfate, and fluoride.     

Solid-Solute Phase Equilibria in Aqueous Solution. XI. Aqueous Solubility and Standard Gibbs Energy of Cadmium Carbonate

The solubilities of CdCO₃ (otavite) in aqueous NaClO₄ solutions have been investigated as a function of ionic strength (0.15 I/mol-kg^–1 5.35, 25°C) and temperature (25°C T 75°C, I = 1.00 mol-kg^–1). A new Chemsage optimization routine was employed to simultaneously evaluate solubility data from this work and other sources, as well as standard electrode potentials determined at different ionic strengths. With the Pitzer equations the solubility constants, , were extrapolated to infinite dilution resulting in log and the ternary ion-interaction parameters ^S_Na,Cd = 0.19 and at 25°C. In addition, the following set of thermodynamic quantities can be derived from the present solubility data for otavite: _f G = –674.2±0.6 kJ-mol^–1; _f H = –755.3±3.4 kJ-mol^–1; S = 93±10 J-mol^–1K^–1. However, the present solubility data are also consistent with a recent determination of the standard entropy of otavite which leads to a recommended set of thermodynamic quantities [_f G (CdCO₃) = –674.2±0.6; _f H (CdCO₃) = –752.1±0.6; S (CdCO₃) = 103.9±0.2].     

Preferential solvation in three component systems: Evaluation of Kirkwood-Buff parameters

The extent of local excess or deficiency of a component solvent near the solute in a mixed binary solvent has been calculated using the Hall formalism for the Kirkwood-Buff equation. The possibility of calculation of the two solute-solvent Kirkwood-Buff parameters using the values is discussed. A model calculation using literature data for preferential solvation in mixed binary solvents is presented. The solute-solvent and solvent-solvent interactions and the relative size of the solvents are also shown to be relevant factors in determining the values.     

On the Pressure and Electric Field Dependencies of the Relative Permittivity of Liquids

The dependencies of the relative permittivity of over 50 liquids on the pressure P, as , and of some 40 liquids on the (square of the) electric field E at ambient conditions, as were obtained from literature data. The function was fitted to a simple expression in and the compressibility, _T. These data were used to obtain the limiting slope for the partial molar volumes and the electrostriction of electrolytes in various solvents.     

Excess molar volumes of 2-methylethylbenzene with benzene,methylbenzene or ethylbenzene at various temperatures

Excess molar volumes of benzene or methylbenzene + 2-methylethylbenzene at 25, 35 and 45°C and of ethylbenzene + 2-methylethylbenzene at 25°C have been determined from density measurements using a vibrating tube densimeter. Experimental V _m ^E values have been compared with calculated values based on the Flory theory.List of Symbols p _i characteristic pressure of pure component - reduced temperature of pure component - V ^E excess molar volume - V _i ^* characteristic volume of pure component - reduced volume of mixture - reduced volume of pure component i - X ₁₂ interaction parameter in Flory's theory - site fraction of component 2 - segment fraction of component 2     

Free-radical addition reactions initiated by metal oxides, VI

CuO catalyzed additions of ethyl cyanoacetate, initiated thermally and by di-tert-butyl peroxide, to 1-decene and ethyl 10-undecylenoate were investigated. The CuO catalyzed reaction proceeds already at 80°C at a high rate, produces 11 adducts in high yields and represents the first example of catalysis in radical addition reactions of non-halogenated compounds.

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1- 10-, CuO, -.-. , CuO, 80°C, 11 . .