Relative Apparent Molar Enthalpies Research Articles

Thermochemical properties of dihydrazidinium bis(tetrazolyl)amine in water and N-methyl pyrrolidone

The enthalpies of dissolution of dihydrazidinium bis(tetrazolyl)amine (DHBTA) in water and N-methyl pyrrolidone (NMP) were measured using a RD496-2000 Calvet microcalorimeter at 298.15 K under atmospheric pressure, respectively. Empirical formulae for the calculation of the enthalpy of dissolution (Δdiss H), relative partial molar enthalpy (Δdiss H partial) and relative apparent molar enthalpy (Δdiss H apparent) were obtained from the experimental data of the dissolution processes of DHBTA in water and NMP. Furthermore, the corresponding kinetic equations describing the two dissolution processes were dα/dt = 10−2.70(1 − α)0.82 for the dissolution of DHBTA in water, and dα/dt = 10−2.47(1 − α)0.66 for the dissolution of DHBTA in NMP, respectively.

The dissolution properties of 2-nitroimino-5-nitrohexahydro-1,3,5-triazine (NNHT) in N,N-dimethyl formamide (DMF)

The enthalpy of dissolution of NNHT in N,N-dimethyl formamide (DMF) was measured by means of a DC08 Calvet microcalorimeter at 298.15 K. Empirical formulae for the calculation of the enthalpy of dissolution (ΔdissH), relative partial molar enthalpy (ΔdissHpartial), and relative apparent molar enthalpy (ΔdissHapparent) were obtained from the experimental data of the enthalpies of dissolution of NNHT in DMF. The kinetic equation that describes the dissolution process of NNHT in DMF at 298.15 K is determined as \( \frac{{{{\rm d}}\alpha }}{{{{\rm d}}t}} = 2.86 \times 10^{ - 3} (1 - \alpha )^{0.94} \).

Study on Thermodynamic Properties of Ionic Liquid 1-Ethyl-3-methylimidazolium Alanine

用中和法合成了氨基酸离子液体1-乙基-3-甲基咪唑丙氨酸([C2mim][Ala]),并利用恒温环境的溶解反应热量计,在(288.15±0.01)K-(308.15±0.01)K温度范围内每隔5K,测定不同质量摩尔浓度离子液体在水中的溶解焓(△sol Hm).根据Archer的方法,通过线性拟合得到了该离子液体的标准摩尔溶解焓(△solHmθ),并计算了其相对表观摩尔溶解焓(ΦL).在298.15 K下,根据Glasser经验方法得到了格子能UPOT=566 kJ· mol-1,并计算了其阴阳离子水化焓值(△H++ △H-)=-620 kJ·mol-1及阴离子水化焓△H-([Ala]-)=-387 kJ· mol-1此外,估算了[C2mim][Ala]水溶液的热容(Cp(sol))和表观摩尔热容(ΦCp).

Crystal structure and thermochemical properties of a novel coordination compound sodium pyruvate C3H3O3Na(s)

A novel coordination compound sodium pyruvate C3H3O3Na(s) is synthesised by a liquid phase reaction. The compound has an obvious bioactivity and can be used as the biological carbon source and the chemical identification of primary and secondary alcohols. It can be also used to determinate transaminase. Elemental analysis and X-ray crystallography are used to characterise the composition and crystal structure of the compound. Single crystal X-ray analysis reveals that the compound is formed by one CH3COCOO− anion and one Na+ cation. An obvious feature of the crystal structure is the formation of the five-membered chelate ring by the coordination of O1 of carboxylate and O3 of keto form with Na+ cation, and it is good for the stability of the compound in structure. The lattice potential energy and ionic volume of the anion are obtained from crystallographic data. In accordance with Hess’ law, a reasonable thermochemical cycle is designed according to the practical synthesis reaction of the compound and the standard molar enthalpy of formation of the compound is calculated as an important physical quantity in chemical thermodynamics by use of an isoperibol solution-reaction calorimeter. Molar enthalpies of dissolution of the compound at various molalities are measured at T=298.15K in the double-distilled water. According to Pitzer’s electrolyte solution theory, molar enthalpy of dissolution of the title compound at infinite dilution is calculated to be ΔsHm∞=(19.81±0.69)kJ·mol−1. The values of relative apparent molar enthalpies (ΦL) and relative partial molar enthalpies of the solvent (L¯1) and the compound (L¯2) at different concentrations m/(mol·kg−1) are derived from the experimental values of the enthalpies of dissolution of the compound.

Dissolution Properties of 3,6-Bis(1H-1,2,3,4-tetrazol-5-yl-amino)-1,2,4,5-tetrazine in N-Methyl Pyrrolidone and Dimethyl Sulfoxide

The molar enthalpies of dissolution for 3,6-bis(1H-1,2,3,4-tetrazol-5-yl-amino)-1,2,4,5-tetrazine (BTATz) were measured in N-methyl-2-pyrrolidone (NMP) and dimethyl sulfoxide (DMSO) using an RD496-2000 Calvet microcalorimeter at 298.15 K under atmospheric pressure. Empirical formulae for the calculation of the molar enthalpies of dissolution (ΔdissH), relative partial molar enthalpies (ΔdissHpartial), and relative apparent molar enthalpies (ΔdissHapparent) were obtained from the experimental results of the dissolution processes of BTATz in NMP or DMSO. Furthermore, the corresponding kinetic equations describing the two dissolution processes are dα/dt = 10−3.55(1 − α)0.57 for the dissolution of BTATz in NMP, and dα/dt = 10−3.74(1 − α)0.63 for the dissolution of BTATz in DMSO, respectively.

Determination of the Molar Enthalpy of Solution for Ionic Liquid [C5mim][OAc](1-pentyl-3-methylimidazolium acetate) in the Temperature Range from 288.15 to 308.15 K

The molar enthalpies of solution, ΔsolHm, for ionic liquid [C5mim][OAc] with different molalities were measured by the solution-reaction isoperibol calorimeter in the temperature range from 288.15 to 308.15 K with an interval of 5 K. According to Archer’s method, the standard molar enthalpies of solution, ΔsolHmθ, and the apparent relative molar enthalpy, ΦL, for [C5mim][OAc] were determined. In terms of Glasser’s theory of lattice energy, the hydration enthalpy of the cation, ΔH+ ([C5mim]+) = −178 kJ·mol–1 was obtained at 298.15 K. Compared with hydration enthalpy of [C2mim]+, ΔH+ ([C2mim]+) = −233 kJ·mol–1, the hydration of [C5mim]+ is weaker than [C2mim]+. The plot of ΔsolHmθ vs (T – 298.15) K is a good straight line and its slope is the standard molar heat capacity of solution, ΔCp,mθ = 231 J·K–1·mol–1, so that the specific heat capacity of solution, ΔCpθ = 1.09 J·g–1·K–1, was obtained for IL [C5mim][OAc].

Thermodynamics of Strong Aqueous Electrolyte Solutions at t = 25 °C Described by the Hückel Equations

A theoretical framework based on the Hückel equation for activity coefficients has been developed, and the physicochemical properties of 57 binary strong electrolyte solutions at t = 25 °C have been correlated. These properties include the activity and osmotic coefficients, apparent molar relative enthalpies, apparent molar heat capacities, and apparent molar volumes. The correlating equations agree well with property values from the literature up to concentrations of m = 2.0 mol kg–1 for 1:1 electrolytes and m = 0.5 mol kg–1 for 2:1, 1:2, and 3:1 electrolytes. Certain electrolytes could not be satisfactorily represented, including polyprotic acids, 2:2 electrolytes, and the zinc and cadmium halides. In addition to quantifying Hückel equation parameters that can be used for the convenient calculation of physicochemical property values, the results provide a benchmark against which other theoretical frameworks with few adjustable parameters can be compared.

Elucidation of Ionic Interactions in the Protic Ionic Liquid Solutions by Isothermal Titration Calorimetry

The strong hydrogen-bonded network noted in protic ionic liquids (PILs) may lead to stronger interactions of the ionic entities of PILs with solvents (water, methanol, ethylene glycol, dimethylsulfoxide (DMSO), N,N'-dimethylformamide (DMF)) as compared with those of aprotic ionic liquids (APILs). The PILs used in this work are 1-methylimidazolium tetrafluoroborate, 2-methylpyridinium tetrafluoroborate, and N-methylpyrrolodinium tetrafluoroborate in comparison to 1-butyl-3-methylimidazolium tetrafluoroborate, which is classified as an APIL. In this work, the excess partial molar enthalpy, H(E)IL obtained from isothermal calorimetric titrations at 298.15 K is used to probe the nature of interactions of the PIL cations with solvent molecules against those present in APIL-solvent systems. This work also reports interesting flip-flopping in the thermal behavior of these PIL-solvent systems depending upon the structure of the cationic ring of a PIL. In some cases, these flip-flops are the specific fingerprints for specific PILs in a common solvent environment. The excess partial molar enthalpy at infinite dilution, H(E,∞)IL, of these PILs bears a critical dependence on the solvent properties. An analysis of relative apparent molar enthalpies, ϕL, of the PIL solutions by the ion interaction model of Pitzer yields important information on ionic interactions of these systems.

Crystal structure and thermochemical properties of a novel coordination compound manganese d-gluconate tetrahydrate

A novel coordination compound of d-gluconic acid with the divalent manganese ion, Mn[(D-C6H11O7)2(H2O)2]·2H2O, is synthesized. The compound has an obvious bioactivity and can be used as a manganese dietary supplements and energy fortifier in medicine and food. Chemical analysis, elemental analysis, and X-ray crystallography are used to characterize its composition, crystal structure and chelating mode of d-gluconic acid with the divalent manganese ion. Single-crystal X-ray analysis reveals that the compound is formed by two d-gluconate anions, one manganese (II) cation, two coordinated waters and two crystal waters. And the two d-gluconate anions in Mn[(D-C6H11O7)2(H2O)2]·2H2O have two different conformations. The compound exhibits the chelate property of d-gluconate anions to manganese (II) cations, and the manganese (II) cation is six-coordinated and chelated by two d-gluconate anions and two coordinated waters. The lattice potential energy and ionic volume of the anion are obtained from crystallographic data. In accordance with Hess’ law, a reasonable thermochemical cycle is designed and the standard molar enthalpy of formation of the compound is calculated as an important physical quantity in relation with the energy state of the compound by use of an isoperibol solution-reaction calorimeter. Molar enthalpies of dissolution of the compound at various molalities are measured at T=298.15K in the double-distilled water. According to Pitzer’s theory, molar enthalpy of dissolution of the title compound at infinite dilution is calculated to be ΔsHm∞=(14.56±0.56)kJ·mol-1. The values of relative apparent molar enthalpies (ΦL) and relative partial molar enthalpies of the solvent (L1‾) and the compound (L2‾) at different concentrations m/(mol·kg−1) are derived from the experimental values of the enthalpies of dissolution of the compound.

Crystal structure, lattice potential energy, and thermochemical properties of a novel compound barium d-gluconate tetrahydrate

A novel compound barium d-gluconate tetrahydrate, Ba[d-C6H11O7]2·4H2O, is synthesized and characterized by chemical analysis, elemental analysis, and X-ray crystallography. Single-crystal X-ray analysis reveals that the compound is formed by two d-gluconate anions, one barium (II) cation and four crystal water molecules. The compound exhibits an outstanding chelate property of d-gluconate anions to barium (II) cations, and the barium (II) cation is ten-coordinated and chelated by six d-gluconate anions. The molecules of the compound are further linked by intermolecular BaO and OH⋯O interactions to form a 3D supramolecular architecture. The lattice potential energy and ionic volume of the anion are obtained from crystallographic data. In accordance with Hess’ law, a reasonable thermochemical cycle is designed and the standard molar enthalpy of formation of Ba[d-C6H11O7]2·4H2O(s) is calculated as ΔsHm [Ba[d-C6H11O7]2·4H2O, s]=−(4712.85±1.06)kJ·mol−1 by use of an isoperibol solution-reaction calorimeter. Molar enthalpies of dissolution of Ba[d-C6H11O7]2·4H2O(s) at various molalities are measured at T=298.15K in the double-distilled water. According to the Pitzer theory, the molar enthalpy of dissolution of the title compound at infinite dilution is calculated to be ΔsHm∞=(49.901±1.212)kJ·mol−1. The values of relative apparent molar enthalpies (appH), relative partial molar enthalpies of the solvent (H¯1) and the compound (H¯2) at different molalities m/(mol·kg−1) are derived from the experimental values of the enthalpies of dissolution of the compound.

Study on the thermodynamic properties for ionic liquid [C4mim][OAc](1-butyl-3-methylimidazolium acetate)

Using the solution-reaction isoperibol calorimeter, molar enthalpies of solution in water, ΔsolHm, for ionic liquid [C4mim][OAc] with different molalities were measured in the temperature range of (288.15–308.15±0.01)K with an interval of 5K. According to Archer's method or Pitzer's electrolyte solution theory, the values of the standard molar enthalpies of solution, ΔsolHmθ, the apparent relative molar enthalpy ΦL, and the parameters βMX(0)L, βMX(1)L were determined for [C4mim][OAc]. According to Krossing's theory of lattice energy, the hydration enthalpy of cation and anion in infinite dilution aqueous [C4mim][OAc] were calculated, (ΔH++ΔH−)=–531.6kJmol−1, at 298.15K. A linear relationship was found by plotting the experimental values of ΔsolHmθ against (T – 298.15)K. The standard molar heat capacity of solution, ΔCp,mθ=339JK−1mol−1 was obtained from the slope of the regression line, and the specific heat capacity of solution, ΔCpθ=1.70Jg−1K−1, was also determined for [C4mim][OAc].

The dissolution properties of N-guanylurea-dinitramide (FOX-12) in dimethyl sulfoxide (DMSO)

The enthalpy of dissolution of FOX-12 in dimethyl sulfoxide (DMSO) was measured by means of a RD496-III Calvet microcalorimeter at 298.15 K. Empirical formulae for the calculation of the enthalpy of dissolution (\( \Updelta_{\text{diss}} H \)), relative partial molar enthalpy (\( \Updelta_{\text{diss}} H_{\text{partial}} \)), and relative apparent molar enthalpy (\( \Updelta_{\text{diss}} H_{\text{apparent}} \)) were obtained from the experimental data of the enthalpies of dissolution of FOX-12 in DMSO. The kinetic equation that describes the dissolution process of FOX-12 in DMSO at 298.15 K is determined as \( \frac{{{\text{d}}\alpha }}{{{\text{d}}t}} = 8.5 \times 10^{ - 3} (1 - \alpha )^{0.59} \).

Dissolution properties of N-guanylurea dinitramide (GUDN) in dimethyl sulfoxide and N-methyl pyrrolidone

The enthalpies of dissolution of N-guanylurea dinitramide (GUDN) in dimethyl sulfoxide (DMSO) and N-methyl-2-pyrrolidone (NMP) were measured using an RD496-2000 Calvet microcalorimeter at 298.15 K under atmospheric pressure, respectively. Empirical formulae for the calculation of the enthalpy of dissolution (ΔdissH), relative partial molar enthalpy (ΔdissHpartial), and relative apparent molar enthalpy (ΔdissHapparent) were obtained from the experimental data of the dissolution processes of GUDN in DMSO and NMP. Furthermore, the corresponding kinetic equations describing the two dissolution processes were dα/dt = 10−3.39(1 − α)0.70 for the dissolution of GUDN in DMSO, and dα/dt = 10−4.06(1 − α)1.11 for the dissolution of GUDN in NMP.

Thermochemical Properties of n-Undecylammonium Bromide Monohydrate C11H28BrNO(s)

The crystal structure of n-undecylammonium bromide monohydrate was determined by X-ray crystallography. The crystal system of the compound is monoclinic, and the space group is P21/c. Molar enthalpies of dissolution of the compound at different concentrations m/(mol·kg−1) were measured with an isoperibol solution–reaction calorimeter at T = 298.15 K. According to the Pitzer’s electrolyte solution model, the molar enthalpy of dissolution of the compound at infinite dilution (\( \Updelta_{\text{sol}} H_{\text{m}}^{\infty } \)) and Pitzer parameters (\( \beta_{\text{MX}}^{(0)L} \) and \( \beta_{\text{MX}}^{(1)L} \)) were obtained. Values of the apparent relative molar enthalpies (\( {}^{\Upphi }L \)) of the title compound and relative partial molar enthalpies (\( \bar{L}_{2} \) and \( \bar{L}_{1} \)) of the solute and the solvent at different concentrations were derived from experimental values of the enthalpies of dissolution.

Crystal structure and thermochemical properties of n-decylammonium ethyl sulfate (C10H21NH3SO4C2H5)(s)

Crystal structure of n-decylammonium ethyl sulfate was determined by X-ray crystallography. Lattice potential energy and molar volume of the solid compound and its anion were respectively obtained. Ionic radius of the anion was calculated from the corresponding effective volume of the anion. Molar enthalpies of dissolution of the compound at different concentrations m /(mol·kg–1) were measured by an isoperibol solution–reaction calorimeter at T=298.15K. According to the Pitzer’s electrolyte solution theory, molar enthalpy of dissolution of the compound at infinite dilution (ΔsolHm∞) was determined to be (21.284±0.042) kJ·mol–1, and enthalpy of hydration of the anion SO4C2H5− was calculated to be ΔH–=−340.68kJ·mol–1. The values of apparent relative molar enthalpies (ΦL) of the title compound and relative partial molar enthalpies (L2¯ and L1¯) of the solute and the solvent at different concentrations were derived from experimental values of enthalpies of dissolution of the compound. Finally, enthalpies of hydration of the compound and its anion were calculated by designing a thermochemical cycle in accordance with lattice potential energy and molar enthalpy of dissolution at infinite dilution.

Crystal structure and thermochemical properties of n-octanammonium oxalate (C8H17NH3)2C2O4(s)

A novel compound n-octanammonium oxalate (C8H17NH3)2C2O4(s) was synthesized by the method of liquid phase reaction. Crystal structure of n-octanammonium oxalate was determined by X-ray crystallography. The lattice potential energy of the compound was calculated to be UPOT=1050.90kJ·mol−1. Molar enthalpies of dissolution of the compound at different concentrations m/(mol·kg−1) were measured by an isoperibol solution–reaction calorimeter at T=298.15K. According to the Pitzer’s electrolyte solution theory, the molar enthalpy of dissolution of the compound at infinite dilution (ΔsolHm∞) and Pitzer parameters (βMX(0)LandβMX(1)L) were obtained. The values of apparent relative molar enthalpies (ΦL) of the title compound and relative partial molar enthalpies (L¯2andL¯1) of the solute and the solvent at different concentrations were derived from experimental values of enthalpies of dissolution. The enthalpy change of the synthesis reaction of n-octanammonium oxalate was determined to be ΔrHmΘ=-(153.68±0.50)kJ·mol-1 by an isoperibol solution–reaction calorimeter, and standard molar enthalpy of formation of (C8H17NH3)2C2O4(s) was calculated to be ΔfHmΘ=-(1463.6±2.4)kJ·mol-1 by using the enthalpies of dissolution and other auxiliary thermodynamic quantities.

Thermodynamic properties of resveratrol in dimethyl sulfoxide

In this article, the enthalpies of dissolution of resveratrol in dimethyl sulfoxide (DMSO) were measured using a RD496-2000 Calvet microcalorimeter at 298.15 K under atmospheric pressure. The differential enthalpy (Δdif H m) and molar enthalpy (Δsol H m) of dissolution of resveratrol in DMSO were determined, and the relationship between heat and the amount of solute was also established. Based on the thermodynamic and kinetic knowledge, the corresponding kinetic equation, half-life, Δsol H m, Δsol S m, Δsol G m, the relative partial molar enthalpy (Δsol H m(partial)) and the relative apparent molar enthalpy (Δsol H m(app)) of the dissolution process were obtained. The results showed that this study not only provided a simple method for the determination of the half-life for a drug, but also offered a theoretical reference for the clinical application of resveratrol.

Study on the enthalpy of solution and enthalpy of dilution for the ionic liquid [C 3mim][Val] (1-propyl-3-methylimidazolium valine)

A new amino acid ionic liquid (AAIL) [C 3mim][Val] (1-propyl-3-methylimidazolium valine) was prepared by the neutralization method. Using the solution-reaction isoperibol calorimeter, molar solution enthalpies of the ionic liquid [C 3mim][Val] with known amounts of water and with different concentrations in molality were measured at T = 298.15 K. In terms of standard addition method (SAM) and Archer’s method, the standard molar enthalpy of solution for [C 3mim][Val] without water, Δ s H m ∘ = (−55.7 ± 0.4) kJ · mol −1, was obtained. The hydration enthalpy of the cation [C 3mim] +, Δ H + ([C 3mim] +) = −226 kJ · mol −1, was estimated in terms of Glasser’s theory. Using the RD496-III heat conduction microcalorimeter, the molar enthalpies of dilution, Δ D H m( m i → m f), of aqueous [C 3mim][Val] with various values of molality were measured. The values of Δ D H m( m i → m f) were fitted to Pitzer’s ion-interaction model and the values of apparent relative molar enthalpy, φL , calculated using Pitzer’s ion-interaction model.

Lattice potential energies and thermochemical properties of triethylammonium halides (Et 3NHX) (X = Cl, Br, and I)

A series of triethylammonium halides (Et 3NHCl, Et 3NHBr, and Et 3NHI) was synthesized. The crystal structures of the three compounds were characterized by X-ray crystallography. The lattice potential energies and ionic radius of the common cation of the three compounds were obtained from crystallographic data. Molar enthalpies of dissolution of the compounds at various values of molality were measured in the double-distilled water at T = 298.150 K by means of an isoperibol solution-reaction calorimeter. According to Pitzer’s theory, the values of molar enthalpies of dissolution at infinite dilution and Pitzer’s parameters of the compounds were obtained. The values of apparent relative molar enthalpies, relative partial molar enthalpies of the solvent and the compounds at different molalities were derived from the experimental values of molar enthalpies of dissolution of the compounds. Finally, hydration enthalpy of the common cation Et 3NH + was calculated to be Δ H + = −(150.386 ± 4.071) kJ · mol −1 by designing a thermochemical cycle.

Crystal Structures and Thermochemical Properties of n-Nonylammonium Dihydrogen Phosphate C9H19NH3·H2PO4(s) and n-Octylammonium Dihydrogen Phosphate C8H17NH3 ·H 2PO4(s)

The crystal structures of n-nonylammonium dihydrogen phosphate and n-octylammonium dihydrogen phosphate were determined by X-ray crystallography. Lattice potential energies of the compounds were obtained from the crystallographic data. The molar enthalpies of dissolution of the two compounds at various molalities in the double-distilled water were measured at T = 298.15 K by means of an isoperibol solution-reaction calorimeter, respectively. According to the Pitzer's electrolyte solution theory, the standard molar enthalpies of dissolution of the two compounds at infinite dilution were determined to be 34.50 kJ·mol–1 and 22.32 kJ·mol–1, and the Pitzer's parameters βMX(0)L and β MX(1)L were obtained. The values of apparent relative molar enthalpies (ΦL) of the title compounds and relative partial molar enthalpies (L2 and L1 of the solute and the solvent at different concentrations were derived from the experimental values of the enthalpies of dissolution of the two compounds.