Standard Molar Heat Capacity Research Articles

An estimation of the effect of mono/poly-hydroxy organic compounds on the interaction of tetradecyltrimethylammonium bromide with levofloxacin hemihydrate antibiotic drug

Observation of the relations of the beta-lactum antibiotic drug levofloxacin hemihydrate (LFH) with of tetradecyltrimethylammonium bromide (TTAB) has been carried out by conductivity measurement technique in aqueous solution of alcohols and polyols at single fixed temperature (303.15 K) for different concentrations and at different temperatures (298.15–318.15 K) with interval of 5.0 K for one selected fixed concentration. For TTAB + LFH mixture with alcohols/polyols, a single critical micelle concentration (cmc) was found in this study. In presence of alcohols, the values of cmc for mixed systems LFH + TTAB exhibited higher (except for ethanol at 298.15 K) in magnitude in compare to their absence. This showed that the micellization of the mixture of LFH and TTAB was unfavorable to some extent in attendance of alcohols. In attendance of polyols, the cmc values for mixed systems LFH + TTAB was obtained smaller in scale in compare to their absence. This exhibited the early micellization of the mixture of LFH and TTAB. Values obtained for ΔG0m were negative, which indicate naturalness of the present study. The other kinds of thermodynamic parameters such as transfer enthalpy (ΔH0m.tr), transfer free energy (ΔG0m.tr), and transfer entropy (ΔS0m.tr) were also observed and demonstrated carefully. The compensation temperature (Tc) as well as the intrinsic enthalpy gain (ΔH0⁎m) were also determined and interpreted. Moreover, the standard molar heat capacity (ΔC0m) for mixed system was evaluated and explained for the studied system.

Standard Partial Molar Heat Capacities and Volumes of Barium and Cadmium Ions in Dimethylformamide at 298.15 K

The heat capacity and bulk properties of barium and cadmium iodide solutions in dimethylformamide (DMF) at 298.15 K are measured via calorimetry and densimetry. Standard partial molar heat capacities $$\bar {C}_{{p,2}}^{^\circ }$$ and volumes $$\bar {V}_{2}^{^\circ }$$ ВаI2 and CdI2 in DMF are calculated. The standard values of heat capacity $$\bar {C}_{{p,i}}^{^\circ }$$ and volume $$\bar {V}_{i}^{^\circ }$$ of barium and cadmium in DMF at 298.15 K were determined.

Standard Partial Molar Heat Capacities and Volumes of Barium and Cadmium Ions in Dimethylsulfoxide at 298.15 K

The heat capacities and volumes of dimethylsulfoxide (DMSO) solutions of barium and cadmium iodides at 298.15 K were measured by calorimetry and densimetry. The standard partial molar heat capacities $$\bar {C}_{{p,2}}^{^\circ }$$ and volumes $$\bar {V}_{2}^{^\circ }$$ of BaI2 and CdI2 in DMSO were calculated. The standard heat capacities $$\bar {C}_{{p,i}}^{^\circ }$$ and volumes $$\bar {V}_{i}^{^\circ }$$ of barium and cadmium ions in DMSO at 298.15 K were determined.

Assessing exchange-correlation functionals for elasticity and thermodynamics of [formula omitted]-[formula omitted]: A density functional perturbation theory study

Elastic and thermodynamic properties of negative thermal expansion (NTE) α-ZrW2O8 have been calculated using PBEsol and PBE exchange-correlation functionals within the framework of density functional perturbation theory (DFPT). Measured elastic constants are reproduced within ∼2% with PBEsol and ∼6% with PBE. The thermal evolution of the Grüneisen parameter computed within the quasi-harmonic approximation exhibits negative values below the Debye temperature, consistent with observation. The standard molar heat capacity is predicted to be CP0=192.2 and 193.8 J mol-1K-1 with PBEsol and PBE, respectively. These results suggest superior accuracy of DFPT/PBEsol for studying the lattice dynamics, elasticity and thermodynamics of NTE materials.

Low-temperature heat capacity and standard thermodynamic functions of 1-butyl-3-methylimidazolium lactate

The heat capacities of 1-butyl-3-methylimidazolium lactate ionic liquids ([C4mim][Lact]) were measured with a highly accurate automatic adiabatic calorimeter over the temperature range from 79 to 406 K. And the experimental values of molar heat capacities were fitted to a polynomial equation using least square method in the appropriate temperature ranges. The standard molar heat capacity was determined to be 1734.46 ± 5.12 J K−1 mol−1 at 298.15 K. The molar enthalpy and molar entropy of the transition were determined to be 15.575 ± 0.045 and 64.44 ± 0.14 J K−1 mol−1. Other thermodynamic properties, such as (HT − H298.15) and (ST − S298.15), were also calculated. Furthermore, when the temperature reaches 241.87 K, the strongest peaks appeared by analysis of the heat capacity curve. This phenomenon could be explained from the interionic interaction, which is the hydrogen bond between the anions and cations.

Low-temperature heat capacities and the thermodynamic functions of ionic liquids 1-heptyl-3-methyl imidazolium perrhenate

Low-temperature heat capacities of the 1-heptyl-3-methyl imidazolium perrhenate ionic liquids have been measured by a high-precision automated adiabatic calorimeter over the temperature range from 78 to 400 K. In this report, the standard molar heat capacity was determined to be 679.438 J K−1 mol−1. The melting temperature at 207.873 ± 0.374 K has been discovered by the heat-capacity curve. The experimental values of molar heat capacities were fitted to two polynomial equations of heat capacities (Cp,m) by least square method. Meanwhile, the thermodynamic functions (HT − H298.15), (ST − S298.15), and (GT − G298.15) were also calculated in the temperature range from 298.15 to 400 K with the interval of 5 K.

Volatility and chemical stability of chromium, molybdenum, and tungsten hexacarbonyls

The sublimation vapor pressures of three metallic (group 6) hexacarbonyls, Cr(CO)6, Mo(CO)6, and W(CO)6, were measured using the Knudsen mass-loss effusion method. The standard (po = 0.1 MPa) molar enthalpies, entropies, Gibbs energies, and heat capacity difference between the gas and solid state, at T = 298.15 K, were derived from the experimental results combined with selected literature ones covering a wide range of temperature. The temperatures and molar enthalpies of fusion of those compounds were measured using differential scanning calorimetry. The thermodynamic stability of the hexacarbonyls was evaluated taking into account the standard Gibbs energies of formation in the crystalline and gaseous phases. Gas-phase absolute entropies, heat capacities, and enthalpies of formation of the three compounds studied as well as the bond distances M–C and C–O were calculated.

Calorimetric insights into the interaction of novel berberrubine derivatives with human telomeric G-quadruplex DNA sequence

Binding of low molecular weight ligands to G-quadruplex nucleic acid structures is known to inhibit telomere extension and prevent abnormal growth of cells leading to cancer. Such specialized DNA conformations have emerged as important targets for drug design and development. In this manuscript we present a detailed calorimetric investigation on the interaction of berberrubine (BBR) and its two synthetic analogues with telomeric G-quadruplex DNA using calorimetry techniques and thermal melting study. A stronger binding of the analogues in comparison with BBR was observed in the experiments. The 13-phenylalkyl derivative of berberrubine (BBR2) (K = 1.38 × 105 M−1) showed higher affinity than the 13-diphenylalkyl derivative of berberrubine (BBR1) (K = 9.70 × 104 M−1). Isothermal titration calorimetry study revealed an exothermic binding that was favoured by both enthalpy and entropy changes in BBR in contrast to the analogues where the binding was mostly enthalpy dominated. A 1:1 binding stoichiometry was revealed in all the systems. The negative standard molar heat capacity values in conjunction with enthalpy–entropy compensation (EEC) confirmed the presence of dominant multiple weak non-covalent interactions in their binding. Differential scanning calorimetry and optical melting study further revealed that BBR and its analogues stabilized quadruplex structure against thermal denaturation. The overall affinity pattern of the alkaloids towards telomeric G-quadruplex structures followed as BBR2 > BBR1 > BBR.

Thermodynamic analysis of the complexation of quinacrine with tRNAPhe

Abstract The thermodynamics of the interaction of the acridine derivative quinacrine with tRNA Phe was studied using isothermal titration calorimetry. The binding was monophasic and exothermic. At (298.15 ± 0.01) K the equilibrium constant was calculated to be (1.76 ± 0.70)·10 5 M −1 . The binding stoichiometry was (0.15 ± 0.04). The binding was predominantly enthalpy driven (Δ H o = −28.39 ± 0.60 kJ·mol −1 ). Salt dependent ITC studies followed by dissection of the standard molar Gibbs energy change showed that the binding reaction was driven by both polyelectrolytic and non-polyelectrolytic forces with the non-polyelectrolytic forces being dominant. Temperature dependent ITC studies showed that the binding became increasingly enthalpy driven with rise in temperature. The binding was characterized by negative standard molar heat capacity change and enthalpy-entropy compensation behaviour.

Heat capacity and thermodynamic functions of TiO 2 (B) nanowires

Abstract Heat capacities of TiO2(B), 50 nm in diameter and several micrometers in length, containing given amounts of anatase were measured using a Quantum Design Physical Property Measurement System (PPMS) over a temperature range from 1.9 to 302 K. After eliminating the contribution from anatase, the heat capacities for TiO2(B) were fitted to a theoretical model in the low temperature range (T 65 K). The standard molar heat capacity, molar entropy, and molar enthalpy for TiO2(B) at T = 298.15 K were determined to be (58.18 ± 0.81) J·K−1·mol−1, (52.31 ± 0.69) J·K−1·mol−1, and (9.03 ± 0.12) kJ·mol−1, respectively, leading to a Gibbs free energy of −(6.56 ± 0.09) kJ·mol−1. The heat capacity of TiO2(B) is found to be similar to brookite, but significantly higher than those of anatase and rutile when temperature is above 200 K.

Heat capacities of some sugar alcohols as phase change materials for thermal energy storage applications

In recent years, sugar alcohols have attracted much attention due to their remarkable phase change properties for thermal energy storage applications. The thermodynamic properties especially the heat capacities would play a crucial role in theoretically and technically investigating the energy storage performance for sugar alcohols. However, as far as we known, the heat capacities of sugar alcohols have never been studied in a wide temperature region. In this study, we have measured the heat capacities of six sugar alcohols of D-mannitol, Myo-Inositol, xylitol, D-arabinitol, L-arabinitol and erythritol in the temperature range from T=(1.9 to 550) K for the first time using a combination of Physical Property Measurement System and differential scanning calorimeter. Based on the heat capacity curve fitting, the standard molar heat capacity, entropy and enthalpy at 298.15K and 0.1MPa, and melting temperature and transition enthalpy in the solid–liquid phase transition region were consequently obtained for these sugar alcohols. Moreover, the heat capacity and phase transition properties obtained in this work were also compared with previous results reported in literature.

Molar heat capacities and thermodynamic functions for difluoromethyleneoxy-bridged liquid crystalline compounds

Differential scanning calorimetry measurements performed in the temperature range of 253–393 K for CF2O linkage liquid crystals reveal existence and stability of the phase transitions. Then, we report molar heat capacities for three difluoromethyleneoxy liquid crystalline compounds measured by the heat-pulse relaxation method within the temperature range from 1.9 to 300 K. The heat capacities of these three compounds increase with the temperature increasing and no thermal anomalies have been found in the whole temperature region. The experimental data have been fitted to a function of temperature with a series of theoretical and empirical models for the proper temperature ranges. Standard thermodynamic properties of these three fluorinated liquid crystals are evaluated from the experimental heat capacity temperature dependencies. The standard molar heat capacities of 3-CB(F,F)XB(F,F)-F, 2-BB(F,F)XB(F,F)-F and 2-BB(F)B(F,F)XB(F,F)-F at 298.15 K and 0.1 MPa have been determined to be $$ C_{{{\text{p}},{\text{m}}}}^{\text{o}} $$ = (560.84 ± 5.61) and (464.41 ± 4.64) and (560.58 ± 5.61) J K−1 mol−1, respectively.

Standard partial molar heat capacities and volumes of aqueous N-methylpiperidine and N-methylpiperidinium chloride from 283 K to 393 K

Densities and volumetric heat capacities for dilute solutions of N-methylpiperidine (N-MP, 0.2mol·kg−1) and N-methylpiperidinium chloride (N-MPH+Cl−, 0.1mol·kg−1) were measured relative to water at 0.1MPa using a vibrating-tube densimeter, and at 0.4MPa using a twin fixed-cell, power-compensation, differential temperature-scanning nano calorimeter, over the temperature ranges 283.15K≤T≤363.15K and 283.15K≤T≤393.15K, respectively. The resulting apparent molar volumes, Vϕ, and heat capacities, Cp,ϕ, were corrected for speciation effects using Young’s rule and extrapolated to infinite dilution using the Debye-Hückel limiting law, Yo≈Yϕ−AYIs1/2, to yield the standard partial molar properties, Yo, for N-MP(aq) and N-MPH+Cl−(aq). The standard partial molar volumes, Vo, and heat capacities, Cpo, were represented by a semi-empirical function of solvent density and temperature, Yo(ρw,T), the “density” model, which can be used to extrapolate these results, as well as other thermodynamic properties for the ionization of N-methylpiperidine, to higher temperatures.

Molar Volumes and Heat Capacities of Aqueous Solutions of Potassium Hydroxide and for Water Ionization up to 573 K at 10 MPa

Densities (ρ) and isobaric volumetric heat capacities (σp) of carefully purified aqueous solutions of potassium hydroxide have been measured at concentrations up to 6 mol·kg–1 at a pressure of 10 MPa over the temperature range 323 ≤ T/K ≤ 573 using a vibrating-tube densimeter and a Tian–Calvet differential calorimeter, respectively. Apparent molar volumes (Vϕ) and isobaric heat capacities (Cpϕ) calculated from these data were fitted with modified Redlich–Meyer type equations to derive the corresponding standard molar volumes and heat capacities at infinite dilution. Exact comparisons with literature data were not possible because of pressure differences but the present values, which greatly extend the database for KOH(aq) in terms of precision, temperature and concentration, are broadly compatible with most of the earlier results. Comparison of the present values of Vϕ and Cpϕ for KOH(aq) with corresponding data for solutions of the other alkali metal hydroxides indicated that all of these systems show si...

Thermodynamics of aqueous adenine: Standard partial molar volumes and heat capacities of adenine, adeninium chloride, and sodium adeninate from T = 283.15 K to 363.15 K

Apparent molar volumes, Vϕ, and apparent molar heat capacities, Cp,ϕ, were measured for aqueous solutions of neutral adenine (AdH) and adeninium chloride (AdH2Cl) at temperatures from 288.15K to 363.15K, and for sodium adeninate (NaAd) at temperatures from 283.15K to 313.15K. Density measurements used in the determination of the standard partial molar volume, Vo, were made with a vibrating-tube densimeter at ambient pressure. Heat capacity measurements used in the determination of the standard partial molar heat capacity, Cpo, were made with a twin fixed-cell, differential output, power compensating, temperature-scanning calorimeter at a pressure of 0.4MPa. The contributions from minor equilibrium species were removed using Young’s Rule to yield values for the standard partial molar volume and heat capacities of the ionic species AdH2+(aq) and Ad−(aq), and the equilibrium mixture of neutral species AdH∗(aq). Semi-empirical equations describing the temperature dependence of Vo and Cpo for each species were fitted by regression to the experimental results. From these equations, the standard partial molar volume change ΔrVom and heat capacity change ΔrCpom for the ionization reactions were calculated. The standard partial molar volumes presented in this study for neutral adenine are the first to be experimentally determined at temperatures above 330K, while the standard partial molar heat capacities are the first to be reported at temperatures above 298.15K. The experimental values for the adeninium cation and adeninate anion are the first to be reported in the literature.

Studies on 3,3′-diamino-4,4′-azofurazan (DAAF)

The specific heat capacity of 3,3′-diamino-4,4′-azofurazan (DAAF) was determined by a differential scanning calorimetry. In the temperature range of 253–373 K, the specific heat capacity (C p) versus T relationship can be fitted into a linear equation: C p (J g−1 K−1) = 0.0028T + 0.26456. The standard molar heat capacity is 215.53 J mol−1 K−1 at 298.15 K. According to the relationship between the specific heat capacity and thermodynamic functions, enthalpy, entropy, Gibbs free energy increments [H T–H 298.15], [S T–S 298.15] and [G T–G 298.15] of DAAF from 253 to 373 K with temperature interval of 10 K, relative to the standard temperature 298.15 K were calculated. The combustion energy of DAAF was measured by a precise IKA C5000 oxygen-bomb calorimeter to be Δc U = −(13188.43 ± 32.77) J g−1. The standard molar enthalpy of combustion at 298.15 K was determined to be Δc H m = −(2575.68 ± 6.42) kJ mol−1. The standard molar enthalpy of formation was calculated to be Δf H m = 429.98 ± 6.44 kJ mol−1 in accordance with Hess’s law. The detonation velocity and detonation pressure were calculated as 7.31 km s−1 and 23.61 GPa using the Kamlet–Jacobs equations according to the experimental enthalpy of formation.

Ionization Constants of DL-2-Aminobutyric Acid and DL-Norvaline Under Hydrothermal Conditions by UV–Visible Spectroscopy

The first and second ionization constants for the amino acids DL-2-aminobutyric acid (DL-2-aminobutanoic acid) and DL-norvaline (DL-2-aminopentanoic acid) were determined under hydrothermal conditions, from 175 to 275 °C at 10 MPa, using thermally-stable colorimetric pH indicators (acridine, 4-nitrophenol and 2-naphthoic acid). The measurements were carried out by UV–visible spectroscopy using a high-temperature, high-pressure platinum flow cell with sapphire windows, which minimized the effects of thermal decomposition. The results were combined with literature values from titration calorimetry at 25–130 °C to yield an extended van’t Hoff model for the temperature dependence of the ionization constants for the carboxylic acid and ammonium groups, \( K_{\text{a,COOH}} \) and \( K_{{{\text{a,NH}}_{3}^{ + } }} \), over the entire temperature range. The experimental results for the second ionization constant \( K_{{{\text{a,NH}}_{3}^{ + } }} \) at elevated temperatures are consistent with the predictions from the Yezdimer–Sedlbauer–Wood functional group additivity model, but for the first ionization constant \( K_{\text{a,COOH}} \) are not. This suggests that the group contribution parameters for the standard partial molar heat capacity of the carboxylic acid group are in error, or that nearest neighbor interactions between the –COOH and \( - {\text{NH}}_{3}^{ + } \) groups cause a breakdown in the functional group additivity relationship.

Critical Evaluation of the Standard Molar Entropies, Enthalpies of Formation, Gibbs Energies of Formation and Heat Capacities of the Aqueous Trivalent Rare Earth Ions, and the Corresponding Standard Molar Entropies, Enthalpies of Formation and Gibbs Energies of Formation of the Thermodynamically Stable RECl3·7H2O(cr) and RECl3·6H2O(cr)

In an earlier evaluation (F.H. Spedding, J.A. Rard, A. Habenschuss, J. Phys. Chem. 81: 1069–1074, 1977) the standard molar entropies of the aqueous trivalent rare earth ions RE3+(aq) were calculated based on the standard molar entropies of the hydrated rare earth chlorides RECl3·7H2O(cr) (RE = La, Pr) and RECl3·6H2O(cr) (RE = Nd, Gd, Tb, Dy, Ho, Er, Lu) at T = 298.15 K and p = 0.1 MPa, along with their corresponding standard molar enthalpies and Gibbs energies of solution, which are known for nearly all of the RECl3·7H2O(cr) and RECl3·6H2O(cr) including YCl3·6H2O(cr). However, the entropies of these RECl3·7H2O(cr) and of several of the RECl3·6H2O(cr) have large uncertainties because the source heat capacities only extend up to T = 223–262 K and not to T = 298.15 K and the crystals used for these measurements contained some occluded solution (water excess). Simple methods are described to correct these entropies of the RECl3·7H2O(cr) and RECl3·6H2O(cr) and to estimate the standard molar entropies of the RECl3·6H2O(cr) from those of the corresponding anhydrous RECl3(cr). By using these entropies, standard molar enthalpies of solution and revised results for the standard molar Gibbs energy changes to form the saturated solutions, revised and CODATA-compatible values of the standard molar entropies of the RE3+(aq), $$ S_{\text{m}}^{\text{o}} ({\text{RE}}^{3 + } ,\,\,{\text{aq}},\,\,298.15\,\,{\text{K}}) $$ where RE = (La, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y), were evaluated or estimated (RE = Pm). By combining these results with critically-assessed standard molar enthalpies of formation of the RE3+(aq), the standard molar Gibbs energies of formation of these trivalent rare earth aquo ions were calculated, as were the corresponding standard molar Gibbs energies and enthalpies of formation of the thermodynamically stable RECl3·7H2O(cr) and RECl3·6H2O(cr) phases at T = 298.15 K and p = 0.1 MPa. In addition, standard molar heat capacities of most of the RE3+(aq) were evaluated from published results for dilute solutions from flow microcalorimetry.

Calorimetric studies on two halogenated uracil isomers

The heat capacities of 6-chlorouracil and 5-chlorouracil isomers were measured using a Quantum Design physical properties measurement system (PPMS) based on a heat pulse relaxation method over the temperature range from (1.9 to 300) K, and the experimental data were fitted as a function of temperature using a series of theoretical and empirical models for the appropriate temperature ranges. The results of these fits were used to calculate thermodynamic function values, Cp,m0, △0TSmo, and △0THmo from T=(0.5 to 300) K. The standard molar heat capacities, entropies and enthalpies of 6-chlorouracil and 5-chlorouracil at 298.15K and 0.1MPa were determined to be Cp,mo=(136.94±1.37) JK−1mol−1 and (137.95±1.38) JK−1mol−1, Smo=(156.87±1.57) JK−1mol−1 and (154.97±1.55) JK−1mol−1 and Hmo=(23.01±0.23) kJmol−1 and (23.07±0.23) kJmol−1, respectively.

Thermodynamics of the induction of self-structure in polyadenylic acid by proflavine

The energetics of self-structure induction in polyadenylic acid in the presence of proflavine has been studied using isothermal titration calorimetry. The self-structure induction process was exothermic and driven by large positive entropy change. The equilibrium constant at T=(298.15±0.01)K and [Na+]=(130±0.01)mM was calculated to be (1.01±0.08)·106M−1. Salt dependent calorimetric studies revealed that the equilibrium constant increased with increasing [Na+] in the 50–130mM range suggesting enhanced binding preference at higher salt concentrations, apparently due to easier self-structure formation at higher [Na+]. Dissection of the standard molar Gibbs energy change clearly established that the self-structure induction was driven by non-polyelectrolytic forces and the polyelectrolytic contribution was relatively small. The equilibrium constant decreased with increasing temperature indicating destabilization of the self-structure at higher temperatures. Negative standard molar heat capacity value obtained from the temperature dependence of the enthalpy change suggested that hydrophobic forces are important for the self-structure induction. Furthermore, a complete enthalpy–entropy compensation phenomenon was also observed.