Thermodynamic Properties of Peptide Solutions. Part 17. Partial Molar Volumes and Heat Capacities of the Tripeptides GlyAspGly and GlyGluGly,and Their Salts K[GlyAspGly] and Na[GlyGluGly] in Aqueous Solution at 25 °C

The partial molar volumes, V^o₂, and partial molar heat capacities, C_p,2^o, at infinite dilution have been determined for the two tripeptides glycylaspartylglycine (glyaspgly) and glycylglutamylglycine (glyglugly), and also for their salts K[glyaspgly] and Na[glyglugly], in aqueous solution at 25 °C. The ionization constants at 25 °C for the aspartyl and glutamyl side-chains have also been determined. These new thermodynamic results have been combined with literature data for electrolytes to obtain the volume and heat capacity changes upon ionization of the acidic side-chains of the peptides. The results are compared with those for other carboxylic acid systems. The partial molar heat capacities and volumes have also been used to calculate the contributions of the acidic amino acid side-chains to the thermodynamic properties.     

Partial Molar Volume,Ionization, Viscosity and Structure of Glycine Betaine in Aqueous Solutions

Densities, partial molar volumes, and viscosities of aqueous solutions of betaine have been measured at 5, 10, 15, 20, 25, 30, 37, and 45 °C over the concentration range 0.05 to 5.0 mol⋅L⁻¹. The partial molar volumes show that betaine exists partly as a monohydrate and partly in its anhydrous form. The proportion of the anhydrous form increases with increasing temperature. Also, an associated form of betaine appears in concentrated betaine solutions, possibly with water as a bridging group. The significance of the viscosity B-coefficient is discussed. The signs of B _st, the increment of the viscosity B-coefficients arising from structural changes of water, are negative and the signs of dB/dT, the temperature derivative of B, are positive. These results show that betaine is a water structure breaker especially at lower temperatures, and this effect decreases to insignificance at higher temperatures. The ionization equilibria of betaine were investigated in aqueous 0.5 mol⋅L⁻¹ and 1.0 mol⋅L⁻¹ NaNO₃ at 5, 15, 25, and 37 °C by a potentiometric method. Using the least-square computer program SUPERQUAD, the complex forms are deduced to be betanium BH, bis(betanium) BHB, and bis(betaine) B₂ or bis(betaine)hydrate BH₂OB.     

Dissociation of Fumaric Acid: Spectrophotometric Investigation in Aqueous Solutions from 10 to 90 <Superscript>∘</Superscript>C and Theoretical Considerations

The dissociation constants of fumaric acid were extracted from UV-vis spectra in the 10–90 ^∘C range. These values were used to extract thermodynamic parameters that showed the temperature effects on the dissociations reactions to be dominantly driven by the solvent. The molar absorption coefficients for the fumaric acid, the bifumarate and fumarate species, can be accurately reproduced with the two-term Gauss–Lorentz equation. Deconvolution of these bands showed strong π–π^∗ transitions for all species and weaker charge-transfer-to-solvent transitions for the charged species. TD-DFT calculations were used to identify the most important molecular orbitals involved in the vertical excitations of the fumaric acid species. The electron population and their states of delocalization were also estimated with topological analyses of the electron density and of the Becke–Edgecombe Electron Localization Function.     

Ionic Interactions of Calcium Sulfate Dihydrate in Aqueous Sodium Chloride Solutions: Solubilities,Densities, Viscosities,Electrical Conductivities,and Surface Tensions at 35 <Superscript>∘</Superscript>C

The thermodynamic, volumetric, transport, and surface properties, solubilities, densities, viscosities, electrical conductivities, and surface tensions of calcium sulfate dihydrate in aqueous sodium chloride solutions have been measured at 35 C, with a view to determine the ionic interactions that occur in these solutions. The experimental density values have been used to calculate the mean apparent molar volumes of the ternary mixtures. Viscosity values have been analyzed using different empirical equations and the experimental values of the viscosity were combined with conductivity to yield the Walden product. Molar surface energies have been computed using experimental surface tension data. The experimental data have been fitted to polynomial equations by a least-squares analysis to obtain the coefficients and their standard errors. Results have been examined in the light of structure making or structure breaking effects of the various ions present in the solutions.     

Molecular Interactions of Macrocycles with Dipeptides in Aqueous Solutions. Partial Molar Volumes and Heat Capacities of Transfer of a Chiral 18-Crown-6 and of a Calix[4]resorcinarene Derivative from Water to Aqueous Dipeptide Solutions at 25°C

Densities and specific heat capacities of ternary aqueous systems containing a dipeptide (alanyl-alanine, alanyl-glutamic acid, alanyl-serine or L-seryl-L-leucine) and a macrocycle (D--manno-naphtho-18-crown-6-ether or 2,8,14,20-tetrakis[-methyl (aminoformyl)]-4,6,10,12,16,18,22,24-octahydroxycalix[4]arene) were determined at 25°C by flow densimetry and flow calorimetry. The partial molar volume and heat capacity of transfer of a macrocycle from water to the dipeptide solution was determined as a function of the dipeptide concentration. Positive values for transfer volumes and transfer heat capacities are observed with all the solutions studied. With the crown ether, except for alanyl-glutamic acid where a 1:1 complex is clearly evidenced due to specific interactions of the side-chain functional group of the peptide with the crown ether, no stoichiometric complexes are confirmed and the partial molar quantities of transfer increase with the hydrophobic character of the dipeptide. Partial quantities of transfer are smaller with the calixarene than with the crown ether and stoichiometric complexes [calixarene]/[dipeptide] from 2:1 to 1:4 are evidenced, depending on the nature and the concentration of the dipeptide.     

Partial Molar Volumes and Partial Molar Isentropic Compressions of <Emphasis Type="Italic">γ</Emphasis>-Butyrolactone and <Emphasis Type="Italic">ε</Emphasis>-Caprolactone at Infinite Dilution in Water at Temperatures (278.15 to 318.15) K and at Atmospheric Pressure

Density and speed-of-sound values at T = (278.15, 283.15, 288.15, 293.15, 298.15, 308.15, and 318.15) K and at atmospheric pressure were measured, for dilute aqueous solutions of γ-butyrolactone and ε-caprolactone, using an Anton Paar DSA 5000 vibrating-tube densimeter and sound analyzer. A small but significant effect of hydrolysis was observed for aqueous ε-caprolactone and a procedure for eliminating its effect was proposed and employed. Values of the partial molar volume and isentropic compression at infinite dilution were obtained from this experimental data by suitable extrapolation procedures and compared with available data from the literature. The group contribution of the methylene group was evaluated and compared with that obtained for other classes of aqueous cyclic solutes.     

Physicochemical Properties of Ampicillin and Amoxicillin as Biologically Active Ligands with Some Alkali Earth,Transition Metal,and Lanthanide Ions in Aqueous and Mixed Solvents at 20, 30, and 40<Superscript>∘</Superscript>C

The acid-base equilibria of ampicillin and amoxicillin were investigated in pure water and different solvent + water mixtures (solvent = methanol, ethanol, acetone, dimethylformamide, and dimethyl sulfoxide) at a constant ionic strength (I = 0.1 mol-dm^–3 KNO₃) and organic solvent volume fractions of 10, 20, and 30%. The effect of temperature on these equilibria was studied at 20, 30, and 40C. Thermodynamic functions of these ligands were calculated and discussed in terms of G, H, and S. The number of ionizable protons was determined using conductometric titrations. The formation constant of the complexes, which form by reaction of the ligands with Mg(II), Ca(II), Zn(II), Cu(II), Ni(II), Co(II), Ce(III), Pr(III), Eu(III), Gd(III), Ho(III), Er(III), and Yb(III), are determined. The relative stability of the alkali earth, transition, and lanthanide elements are compared with each other and discussed in terms of the ionic radius and the electronic structure of the outer shell of that ion. The results obtained are discussed in terms of macroscopic properties of the mixed solvents and the possible variation in microheterogenity of the solvation shells around the solute.     

Solubility of <Emphasis Type="Italic">d</Emphasis>-Element Salts in Organic and Aqueous–Organic Solvents: VI.<Superscript>1</Superscript> Structure and Thermal Stability of Cadmium Iodide and Bromide Solvates with Dimethylacetamide and Dimethylformamide

Five solvates, [CdBr₂(DMF)] _n , [CdBr₂(DMA)] _n , [CdI²(DMF)] ⁿ , [Cd(DMF)₆][Cd₂I₆], and {[Cd(DMA)₆][Cd₅I₁₂] _n } _m , were isolated from the ternary systems CdX₂–L–H₂O (X = Br, I; L = N,N-dimethylacetamide, N,N-dimethylformamide) and characterized by the X-ray single crystal analysis. The structures of the first three solvates is similar to each other in structures and represent a one-dimensional polymer chain, the fourth solvate has the discrete structure containing [Cd(DMF)₆]²⁺ and [Cd₂I₆]^2– ions, and the fifth solvate contains discrete [Cd(DMA)₆]²⁺ cations and the polymer anionic fragment [Cd₅I₁₂] _n ^2n–.     

Understanding the Solid Solution–Aqueous Solution Equilibria in the KCl + RbCl + H<Subscript>2</Subscript>O System from Experiments,Atomistic Simulation and Thermodynamic Modeling

The solid solution–aqueous solution (SSAS) equilibria in the KCl + RbCl + H₂O system were redetermined at 298.15 K. The experimental data for (K,Rb)Cl were consistent with the formation of a continuous solid solution without miscibility gaps. The Schreinemakers’ wet residues method and an XRD quantitative analysis technique based on the Vegard approach were applied to determine the chemical composition of the solid solution phase of (K,Rb)Cl. The compositions of (K,Rb)Cl derived from the Vegard approach are in accordance with those from the wet residues method. The thermodynamic properties of mixing of the (K,Rb)Cl solid solution were theoretically predicted using atomistic simulations. From these simulations, a regular solution behavior is recognized that is consistent with the knowledge of the thermodynamic properties of mixing of (K,Rb)Cl obtained from SSAS equilibrium studies, but the predicted regular solution model parameter A ₀ is significantly larger than that regressed from the SSAS equilibrium data. Finally, a thermodynamic model was developed for representing the SSAS equilibria and element partitioning in the KCl + RbCl + H₂O system as a function of temperature that can be used for predicting the SSAS equilibria in the studied system over the temperature range 273.15–373.15 K.     

Ion Selective Electrode Determination of Free Versus Total Fluoride Ion in Simple and Fluoroligand Coordinated Hexafluoropnictate (PnF<Subscript>6</Subscript><Superscript>−</Superscript>, Pn = P,As, Sb,Bi) Salts

Interpretation of the results of determinations of free fluoride (F_f⁻) and total fluoride (F_t⁻) obtained with fluoride ISE while conducting elemental chemical analysis of bulk material of newly synthesized inorganic fluoride compounds is of crucial importance for the purpose of determination of purity and stoichiometry of these compounds. Knowledge of the properties and behavior of these compounds in aqueous media is therefore essential. Observations are presented on the determinations of the amounts of F_t⁻ and F_f⁻ in fluorinated compounds, in the particular hexafluoropnictate salts (PnF₆⁻, Pn = P, As, Sb, Bi) as found in aqueous media and in some compounds with XeF₂, AsF₃ ligands. A critical look at the determined amounts of F_f⁻, F_t⁻and calculated amounts of bound fluoride (F_b⁻) is provided.     

The Partial Molar Isothermal Compressions of the Nucleosides Adenosine,Cytidine, and Uridine in Aqueous Solution at <Emphasis Type="Italic">T</Emphasis> = (288.15 and 313.15) K

Sound speeds have been measured for aqueous solutions of the nucleosides adenosine, cytidine, and uridine at T = (288.15 and 313.15) K and at ambient pressure. The partial molar isentropic compressions at infinite dilution, \( K_{S,2}^{\text{o}} \), were derived from the speed of sound data. The partial molar heat capacities at infinite dilution, \( C_{p,2}^{\text{o}} \), for the three nucleosides at T = (288.15 and 313.15) K were also determined. These \( K_{S,2}^{\text{o}} \) and \( C_{p,2}^{\text{o}} \) results, along with partial molar isobaric expansions at infinite dilution, \( E_{2}^{\text{o}} = \, (\partial V_{2}^{\text{o}} /\partial T)_{p} \), that were derived using data from the literature, were used to evaluate the partial molar isothermal compressions at infinite dilution, \( K_{T,2}^{\text{o}} \{ K_{T,2}^{\text{o}} = - \, (\partial V_{2}^{\text{o}} /\partial p)_{T} \} \), for the nucleosides. The \( K_{T,2}^{\text{o}} \) results were rationalized in terms of nucleoside hydration and its temperature dependence.     

Syntheses and structures of 1d coordination polymers based on cluster anions [Re<Subscript>4</Subscript>Te<Subscript>4</Subscript>(CN)<Subscript>12</Subscript>]<Superscript>4–</Superscript> and cationic Ln<Superscript>3+</Superscript> (Ln = La,Gd) complexes with 1,10-phenanthroline

Two new porous coordination polymers based on cluster anions [Re₄Te₄(CN)₁₂]^4– and cationic Ln³⁺ (Ln = La, Gd) complexes with 1,10-phenanthroline (Рhen) are synthesized under hydrothermal conditions. The structures of the compounds are determined by X-ray diffraction analysis (CIF files CCDC 1437445 (I) and 1437446 (II)). Compound (РhenH)[{La(H₂O)₃(Рhen)₂}{Re₄Te₄(CN)₁₂}] · 1.5Рhen · 6H₂O (I) crystallizes in the space group \(P\bar 1\) (triclinic system): a = 13.322(3), b = 15.977(3), c = 18.576(4) Å, α = 71.34(3)°, β = 85.56(3)°, γ = 88.27(3)°, V = 3734.8(13) ų. Compound (PhenH)[{Gd(H₂O)₂(Phen)₂}{Re₄Te₄(CN)₁₂}] · 2Phen · 0.5H₂O (II) crystallizes in the space group C2/c (monoclinic crystal system): a = 18.146(1), b = 30.245(2), c = 13.455(2) Å, β = 97.858(2)°, V = 7315.4(1) ų. Structures I and II are based on polymer chains consisting of alternating fragments [Re₄Te₄(CN)₁₂]^4– and {Ln(H₂O) _n (Phen)₂}³⁺ (Ln = La, n = 3; Ln = Gd, n = 2) linked by the bridging CN ligands. The packings of the polymers contain extended channels due to the developed network of noncovalent interactions. The walls of the channels are formed by both hydrophilic (CN^–) and hydrophobic (Рhen) groups. The channels, whose volume is 25 and 15% for compounds I and II, respectively, are filled by disordered Phen molecules and PhenH⁺ cations, as well as by H₂O molecules.     

Host-guest complexes of a water soluble cucurbit[6]uril derivative with some dications of 1,ω-alkyldipyridines: <Superscript>1</Superscript>H NMR and X-ray structures

Interactions between a symmetrical tetramethyl-substituted cucurbit[6]uril (host: TMeQ[6]) and 1,ω-alkylenedipyridine (ω = 2, 4, 6, 8, 10) dicationic guests were investigated using ¹H NMR spectroscopy and single crystal X-ray crystallography. In these inclusion complexes, combined cavity and portal binding in TMeQ[6] were observed, and the length of the bridged alkylene was found to play an important role not only in balancing the overall hydrophilic/hydrophobic interaction between the host and the guest, but also in defining the structure of the resulting inclusion complexes. For the guest 1,2-ethylenedipyridine (Edpy), TMeQ[6] includes a positively charged pyridine ring of Edpy to form an unsymmetrical inclusion complex; for the guest 1,4-butylenedipyridine (Bdpy), TMeQ[6] includes a positively charged pyridine ring of Bdpy, but the different competitive interactions in and between the related inclusion complexes could lead to a fast exchange between the hosts and guests. For the guests with longer bridge chains, such as 1,6-hexamethylenedipyridine (Hdpy) or 1,8-octylenedipyridine (Odpy), a stable pseudorotaxane inclusion complex is formed by combining the hydrophobic cavity and the outer portal dipole-ion interactions. However, for 1,10-decatylenedipyridine (Ddpy), the two TMeQ[6] host molecules include the two end pyridine rings of Ddpy and form a dumbbell inclusion complex. Supported by the National Natural Science Foundation of China (Grant Nos. 20662003 & 20767001), the International Collaborative Project of Guizhou Province (Grant No. 2007400108), the Science Technology Fund of Guizhou Province (Grant No. J-2008-2012) and the Natural Science Youth Foundation of Guizhou University (Grant No. 2007-005)     

Experimental and Theoretical Determination of the Limiting Partial Molar Volume of Indole in CCl<Subscript>4</Subscript>, Tetrahydrofuran and Acetonitrile at 293.15 K: A Comparative Study with Benzimidazole and Benzothiophene

The partial molar volumes of indole(Ind) at infinite dilution (V₂^￥V_{2}^{\infty}) in carbon tetrachloride (CCl₄), acetonitrile (ACN) and tetrahydrofuran (THF) as solvents, were estimated from densitometry measurements at 293.15 K. The results indicate that $V_{2}^{\infty}\mbox{(ACN)}>V_{2}^{\infty}\mbox{(CCl$V_{2}^{\infty}\mbox{(ACN)}>V_{2}^{\infty}\mbox{(CCl $\approx V_{2}^{\infty}\mbox{(THF)}$\approx V_{2}^{\infty}\mbox{(THF)}. The values determined in this study are close to the values calculated from reported density for Ind in the solid state. In order to make a comparison the partial molecular volume of benzimidazole (Bim) and benzothiophene (BT) in solvents with appropriate solubility were measured too, and the results have revealed that $V_{2}^{\infty}\mbox{(BT)}>V_{2}^{\infty}\mbox{(Ind)}$V_{2}^{\infty}\mbox{(BT)}>V_{2}^{\infty}\mbox{(Ind)} in CCl₄ and $V_{2}^{\infty}\mbox{(Ind)}>V_{2}^{\infty}\mbox{(Bim)}$V_{2}^{\infty}\mbox{(Ind)}>V_{2}^{\infty}\mbox{(Bim)} in THF. In this work the role of solvent reorganization around to solute cavity, and specific and nonspecific interactions on the volumetric behavior of these molecules in solution are discussed using the Terasawa-Itsuki-Arakawa model, the Lee-Graziano model, molar volumes of solutes calculated at the DFT-B3LYP/cc-pVTZ and aug-cc-pVTZ level in the gas phase and considering solvent presence with the Onsager’s reaction field, and the van der Waals volume. This analysis suggests that the molecular volumes of solutes are overestimated by the quantum methods employed in this work and that the volumetric contribution from the van der Waals components to the limiting partial molecular volumes of solutes is important, with the exception of Ind in CCl₄ where the solvent reorganization is the dominant factor.     

Synthesis and structure of isomeric (μ-H)Os<Subscript>3</Subscript>(μ,η<Superscript>2</Superscript>-(O,N)-6,6-clusters of dimethyl-2-methylene-bicyclo[3.1.1]heptan-3-one oxime)(CO)<Subscript>10</Subscript>. Crystal structure of one of the isomers

(-H)₂Os₃(,²-(O,N)-6,6-dimethyl-2-methylene-bicyclo[3.1.1]heptan-3-one oxime)(CO)₁₀ isomeric clusters have been synthesized, separated chromatographically, and investigated by IR and NMR spectroscopy. The crystal structure of one of the isomers has been determined (Enraf-Nonius CAD-4 automatic diffractometer, graphite monochromator, MoK , /2 scan mode at a variable rate). The crystals are monoclinic with unit cell parameters: a = 9.125(2) , b = 13.629(3) , c = 10.098(2) , = 90.16(3)°, V = 1255.8(4) ³, space group P2₁, Z = 2, composition (-H)₂Os₃(,²-ONC₁₀H₁₄)(CO)₁₀, d _calc = 2.647 g/cm³. The structure is molecular; the planes of the Os₃ triangle and the OsONOs bridging ligand are linked according to the butterfly pattern with an angle of 102.0° between the planes. The Os-Os bonds vary within the range 2.840 –2.882 .Original Russian Text Copyright © 2004 by V. A. Maksakov, N. V. Pervukhina, S. V. Korenev, N. V. Podberezskaya, V. P. Kirin, and A. V. TkachevTranslated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 4, pp. 698–705, July–August, 2004.This revised version was published online in April 2005 with a corrected cover date.     

Condensation of N-monosubstituted 2-naphthylamines,formaldehyde, and cyclic β-diketones. One-pot synthesis of 2,4-disubstituted derivatives of 1,2,3,4-tetrahydrobenzo[<Emphasis Type=Italic>f</Emphasis>]quinoline

Various spirocyclic derivatives of 1,2,3,4-tetrahydrobenzo[f]quinoline containing substituents in the positions 2 and 4 of the ring were obtained by one-pot multicomponent condensation of available N-benzyl-2-naphthylamines, formaldehyde, and cyclic β-diketones of cyclohexanedione series.