Heat capacities and thermodynamic properties of 2-benzoylpyridine (C12H9NO)

The heat capacities of 2-benzoylpyridine were measured with an automated adiabatic calorimeter over the temperature range from 80 to 340 K. The melting point, molar enthalpy, Δ_fusH^m, and entropy, Δ_fusS^m, of fusion of this compound were determined to be 316.49±0.04 K, 20.91±0.03 kJ mol^–1 and 66.07±0.05 J mol^–1 K^–1, respectively. The purity of the compound was calculated to be 99.60 mol% by using the fractional melting technique. The thermodynamic functions (H_T–H_298.15) and (S_T–S_298.15) were calculated based on the heat capacity measurements in the temperature range of 80–340 K with an interval of 5 K. The thermal properties of the compound were further investigated by differential scanning calorimetry (DSC). From the DSC curve, the temperature corresponding to the maximum evaporation rate, the molar enthalpy and entropy of evaporation were determined to be 556.3±0.1 K, 51.3±0.2 kJ mol^–1 and 92.2±0.4 J K^–1 mol^–1, respectively, under the experimental conditions.     

Preparation and characterization of anion-cation surfactants modified montmorillonite

The low-temperature molar heat capacities of CoPc and CoTMPP were measured by temperature modulated differential scanning calorimetry (TMDSC) over the temperature range from 223 to 413 K for the first time. No phase transition or thermal anomaly was observed in the experimental temperature range for CoPc. However, a structural change was found to be nonreversible for CoTMPP in the temperature range of 368–403 K, which was further validated by the results of IR and XRD. The molar enthalpy ΔH _m and entropy ΔS _m of phase transition of the CoTMPP were determined to be 3.301 kJ mol⁻¹ and 8.596 J K⁻¹ mol⁻¹, respectively. The thermodynamic parameters of CoPc and CoTMPP such as entropy and enthalpy relative to reference temperature 298.15 K were derived based on the above molar heat capacity data. Moreover, the thermal stability of these two compounds was further investigated through TG measurements. Three steps of mass loss were observed in the TG curve for CoPc and five steps for CoTMPP.     

Thermochemical studies on the thioproline

The combustion energy of thioproline was determined by the precision rotating-bomb calorimeter at 298.15 K to be Δ_c U= –2469.30±1.44 kJ mol^–1. From the results and other auxiliary quantities, the standard molar enthalpy of combustion and the standard molar enthalpy of formation of thioproline were calculated to be Δ_c H _m ^θC₄H₇NO₂S, (s), 298.15 K= –2469.92±1.44 kJ mol^–1 and Δ_f H _m ^θC₄H₇NO₂S, (s), 298.15K= –401.33±1.54 kJ mol^–1.     

Thermal properties of seed proteins

The sample of LiCoO₂ was synthesized, and the heat capacity was measured by adiabatic calorimetry between 13 and 300 K. The smoothed values of the heat capacity were calculated from the data. The thermodynamic functions, standard enthalpy, entropy and Gibbs energy, of LiCoO₂ were calculated from the heat capacity and the numerical values are tabulated at selected temperatures from 15 to 300 K. The heat capacity, enthalpy, entropy, and Gibbs energy at T=298.15 K are 71.57 J K^–1mol^–1, 9.853 kJ mol^–1, 52.45 J K^–1 mol^–1, –5.786 kJ mol^–1, respectively. This revised version was published online in August 2006 with corrections to the Cover Date.     

Lithium sulfate: Calorimetric determination of the temperatures and enthalpies of high-temperature phase transitions

Using a high-temperature Calvet calorimeter as a differential enthalpic analyser Li₂SO₄ was investigated in the temperature range 800–1200 K. One transformation in the solid state was observed at 847 K with a corresponding enthalpy increment of 24.2 kJ mol^?1. The solid-liquid transition was found to occur at 1131 K with an enthalpy of fusion of 7.74 kJ mol^?1. Furthermore, the analysis of the corresponding thermograms supports the presence of the premelting effect which was evidenced by other techniques. A critical comparison with previous results in the literature is given.     

Thermodynamics of the conversion of aqueous glucose to fructose

The thermodynamics of the conversion of aqueous glucose to fructose has been investigated using both heat conduction microcalorimetry and high pressure liquid chromatography (HPLC). The reaction was carried out in both aqueous Tris/HCl buffer and in aqueous phosphate buffer in the pH range 7–8 using the enzyme glucose isomerase and the cofactors CoCl₂ and MgSO₄. The temperature range over which this reaction was investigated was 298.15–358.15 K. We have found that the enthalpy of reaction is independent of pH over the range investigated. A combined analysis of both the HPLC and microcalorimetric data leads to the following results at 298 15 K:ΔG° = 349 ± 53 J mol^-1, ΔH° = 2.78 ± 0.20 kJ mol^-1, and ΔC _p ^° = 76 ± 30 J mol^-1 K^-1. The stated uncertainties are based upon an analysis of both the random and systematic errors inherent in the measurements. Comparisons are made with literature data. The percent conversion of glucose to fructose has been calculated for the temperature range 300–373.15 K.     

Thermodynamic investigation of room temperature ionic liquid

The molar heat capacities of the room temperature ionic liquid 1-butylpyridinium tetrafluoroborate (BPBF₄) were measured by an adiabatic calorimeter in temperature range from 80 to 390 K. The dependence of the molar heat capacity on temperature is given as a function of the reduced temperature X by polynomial equations, C _p,m [J K⁻¹ mol⁻¹]=181.43+51.297X −4.7816X ²−1.9734X ³+8.1048X ⁴+11.108X ⁵ [X=(T−135)/55] for the solid phase (80–190 K), C _p,m [J K⁻¹ mol⁻¹]= 349.96+25.106X+9.1320X ²+19.368X ³+2.23X ⁴−8.8201X ⁵ [X=(T−225)/27] for the glass state (198–252 K), and C _p,m[J K⁻¹ mol⁻¹]= 402.40+21.982X−3.0304X ²+3.6514X ³+3.4585X ⁴ [X=(T−338)/52] for the liquid phase (286–390 K), respectively. According to the polynomial equations and thermodynamic relationship, the values of thermodynamic function of the BPBF₄ relative to 298.15 K were calculated in temperature range from 80 to 390 K with an interval of 5 K. The glass transition of BPBF₄ was observed at 194.09 K, the enthalpy and entropy of the glass transition were determined to be ΔH _g=2.157 kJ mol⁻¹ and ΔS _g=11.12 J K⁻¹ mol⁻¹, respectively. The result showed that the melting point of the BPBF₄ is 279.79 K, the enthalpy and entropy of phase transition were calculated to be ΔH _m = 8.453 kJ mol⁻¹ and ΔS _m=30.21 J K⁻¹ mol⁻¹. Using oxygen-bomb combustion calorimeter, the molar enthalpy of combustion of BPBF₄ was determined to be Δ_c H _m⁰ = −5451±3 kJ mol⁻¹. The standard molar enthalpy of formation of BPBF₄ was evaluated to be Δ_f H _m⁰ = −1356.3±0.8 kJ mol⁻¹ at T=298.150±0.001 K.     

Thermodynamic and kinetic behaviour of salicylsalicylic acid

The thermal behaviour of salicylsalicylic acid (CAS number 552-94-3) was studied by differential scanning calorimetry (DSC). The endothermic melting peak and the fingerprint of the glass transition were characterised at a heating rate of 10°C min^-1. The melting peak showed an onset at T _on = 144°C (417 K) and a maximum intensity at T _max = 152°C (425 K), while the onset of the glass transition signal was at T _on = 6°C. The melting enthalpy was found to be Δ_mH = 28.9±0.3 kJ mol^-1, and the heat capacity jump at the glass transition was ΔC _P = 108.1±0.1 J K^-1mol^-1. The study of the influence of the heating rate on the temperature location of the glass transition signal by DSC, allowed the determination of the activation energy at the glass transition temperature (245 kJ mol^-1), and the calculation of the fragility index of salicyl salicylate (m = 45). Finally, the standard molar enthalpy of formation of crystalline monoclinic salicylsalicylic acid at T = 298.15 K, was determined as Δ_fH_m ^o(C₁₄H₁₀O₅, cr) = - (837.6±3.3) kJ mol^-1, by combustion calorimetry. This revised version was published online in August 2006 with corrections to the Cover Date.     

Standard molar enthalpies of formation and sublimation of <Emphasis Type="Italic">N</Emphasis>-phenylphthalimide

The standard (p ⁰=0.1 MPa) molar enthalpy of formation, Δ_f H ⁰ _m, for crystalline N-phenylphthalimide was derived from its standard molar enthalpy of combustion, in oxygen, at the temperature 298.15 K, measured by static bomb-combustion calorimetry, as –206.0±3.4 kJ mol^–1. The standard molar enthalpy of sublimation, Δ^g _cr H ⁰ _m , at T=298.15 K, was derived, from high temperature Calvet microcalorimetry, as 121.3±1.0 kJ mol^–1. The derived standard molar enthalpy of formation, in the gaseous state, is analysed in terms of enthalpic increments and interpreted in terms of molecular structure.     

Gaseous complexes of cobalt(II) bromide and pyridine

The stepwise decomposition of CoBr₂py₂(s) has been investigated on a thermobalance by the “modified entrainment” method yielding Δ₁H=88.6 kJ mol¹, Δ₁S=156.6 JK^?1 mol^?1 and Δ₂H=119.0 kJ mol^?1, Δ₂S=211.8 JK^?1 mol^?1 for the dissociation of the first and second pyridine. The evaporation of CoBr₂py₂(l) and the association of gaseous pyridine to CoBr₂py(l) forming CoBr₂py₂(g) has been studied by vis spectroscopy at 250?420°C. By combining the new results with literature values, a complete thermodynamic cycle for the solid-liquid-gas equilibria in the CoBr₂-pyridine system could be established. It shows that in solution the formation of CoBr₂py₂ is not determined by the cobalt-pyridine bond energy but by the solvation energy of the rectants.     

Binding properties and structural changes of human growth hormone upon interaction with cobalt ion

Binding properties and structural changes of human growth hormone (hGH) due to the interaction by cobalt ion (Co²⁺) were done at 27°C in NaCl solution, 50 mM, using different techniques of UV-Vis spectroscopy, circular dichroism (CD), isothermal titration calorimetry (ITC) and differential scanning calorimetry (DSC) techniques. There is a set of three identical and non-interacting binding sites for cobalt ions. The intrinsic association equilibrium constant and the molar enthalpy of binding obtained by ITC are 0.80 mM⁻¹ and −16.70 kJ mol⁻¹, respectively. The intrinsic association equilibrium constant obtained by a standard isothermal titration UV-Vis spectrophotometry method is also 0.79 mM⁻¹, which is in good agreement with the value obtained from ITC. The Gibbs free energy and entropy changes due to the binding of cobalt ion on hGH are −16.67 kJ mol⁻¹ and −0.1 J K⁻¹ mol⁻¹, respectively. Energetic domains analysis by DSC shows that phase transition of hGH in the presence of cobalt occurs at one main transition. Deconvolution of the main transition provides two sub-transitions with different values of the melting point and enthalpy of unfolding (33°C and 164 kJ mol⁻¹ for the first and 49°C and 177 kJ mol⁻¹ for the second, respectively). Interaction of cobalt ions with hGH prevents aggregation by an affect on the hydrophobicity of the protein macromolecule and provide useful information about its structure due to becoming reversible of protein thermal denaturation.     

Thermochemical study of the solid complex Ho(PDC)3 (o-phen)

A novel solid complex, formulated as Ho(PDC)₃ (o-phen), has been obtained from the reaction of hydrate holmium chloride, ammonium pyrrolidinedithiocarbamate (APDC) and 1,10-phenanthroline (o-phen·H₂O) in absolute ethanol, which was characterized by elemental analysis, TG-DTG and IR spectrum. The enthalpy change of the reaction of complex formation from a solution of the reagents, Δ_rH_m^θ (sol), and the molar heat capacity of the complex, c_m, were determined as being –19.161±0.051 kJ mol^–1 and 79.264±1.218 J mol^–1 K^–1 at 298.15 K by using an RD-496 III heat conduction microcalorimeter. The enthalpy change of complex formation from the reaction of the reagents in the solid phase, Δ_rH_m^θ(s), was calculated as being (23.981±0.339) kJ mol^–1 on the basis of an appropriate thermochemical cycle and other auxiliary thermodynamic data. The thermodynamics of reaction of formation of the complex was investigated by the reaction in solution at the temperature range of 292.15–301.15 K. The constant-volume combustion energy of the complex, Δ_cU, was determined as being –16788.46±7.74 kJ mol^–1 by an RBC-II type rotating-bomb calorimeter at 298.15 K. Its standard enthalpy of combustion, Δ_cH_m^θ, and standard enthalpy of formation, Δ_fH_m^θ, were calculated to be –16803.95±7.74 and –1115.42±8.94 kJ mol^–1, respectively.     

Molar heat capacities and standard molar enthalpy of formation of 2-amino-5-methylpyridine

The heat capacities (C _p,m) of 2-amino-5-methylpyridine (AMP) were measured by a precision automated adiabatic calorimeter over the temperature range from 80 to 398 K. A solid-liquid phase transition was found in the range from 336 to 351 K with the peak heat capacity at 350.426 K. The melting temperature (T _m), the molar enthalpy (Δ_fus H _m⁰), and the molar entropy (Δ_fus S _m⁰) of fusion were determined to be 350.431±0.018 K, 18.108 kJ mol⁻¹ and 51.676 J K⁻¹ mol⁻¹, respectively. The mole fraction purity of the sample used was determined to be 0.99734 through the Van’t Hoff equation. The thermodynamic functions (H _T-H _298.15 and S _T-S _298.15) were calculated. The molar energy of combustion and the standard molar enthalpy of combustion were determined, ΔU _c(C₆H₈N₂,cr)= −3500.15±1.51 kJ mol⁻¹ and Δ_c H _m⁰ (C₆H₈N₂,cr)= −3502.64±1.51 kJ mol⁻¹, by means of a precision oxygen-bomb combustion calorimeter at T=298.15 K. The standard molar enthalpy of formation of the crystalline compound was derived, Δ_r H _m⁰ (C₆H₈N₂,cr)= −1.74±0.57 kJ mol⁻¹.     

Enthalpic analysis of the CaTiSiO5 system

The relative enthalpy of titanite and enthalpy of CaTiSiO₅ melt have been measured using drop calorimetry between 823 K and 1843 K. Enthalpies of solution of titanite and CaTiSiO₅ glass have been measured by the use of hydrofluoric acid solution calorimetry at 298 K. Enthalpy of vitrification at 298 K, δ_vitr H(298 K) = (80.7 ± 3.4) kJ mol⁻¹, and enthalpy of fusion at the temperature of fusion 1656 K, δ_fus H(1656 K) = (139 ± 3) kJ mol⁻¹, of titanite have been determined from experimental data. The obtained enthalpy of fusion is considerably higher than up to the present published values of this quantity.     

Determination of specific heat capacity and standard molar combustion enthalpy of taurine by DSC

Using XRY-1C calorimeter, the standard molar enthalpy of taurine was determined to be ?2546.2?kJ?mol^?1 . The reliability of the instrument used was tested by using naphthalene as reference material; and through comparing the molar combustion enthalpy of naphthalene measured with its standard value found in literature, the absolute error and relative error were found to be 4.53?kJ?mol^?1 and 0.09%, respectively. The melting point and melting enthalpy of taurine were determined by Differential Scanning Calorimetry (DSC), which was found to be 588.45?K and ?22.197?kJ?mol^?1, respectively. Moreover, using the DSC method, the specific heat capacities C _p of taurine was measured and the relationship between C _p and temperature was established. The thermodynamic basic data obtained are available for the exploiting new synthesis method, engineering design and industry production of taurine.     

The structure and thermochemistry of 3:4,5:6-dibenzo-2-hydroxymethylene-cyclohepta-3,5-dienenone (1) and some related compounds

Condensed and gas phase enthalpies of formation of 3:4,5:6-dibenzo-2-hydroxymethylene-cyclohepta-3,5-dienenone (1, (−199.1 ± 16.4), (−70.5 ± 20.5) kJ mol⁻¹, respectively) and 3,4,6,7-dibenzobicyclo[3.2.1]nona-3,6-dien-2-one (2, (−79.7 ± 22.9), (20.1 ± 23.1) kJ mol⁻¹) are reported. Sublimation enthalpies at T=298.15 K for these compounds were evaluated by combining the fusion enthalpies at T = 298.15 K (1, (12.5 ± 1.8); 2, (5.3 ± 1.7) kJ mol⁻¹) adjusted from DSC measurements at the melting temperature (1, (T _fus, 357.7 K, 16.9 ± 1.3 kJ mol⁻¹)); 2, (T _fus, 383.3 K, 10.9 ± 0.1) kJ mol⁻¹) with the vaporization enthalpies at T = 298.15 K (1, (116.1 ± 12.1); 2, (94.5 ± 2.2) kJ mol⁻¹) measured by correlation-gas chromatography. The vaporization enthalpies of benzoin ((98.5 ± 12.5) kJ mol⁻¹) and 7-heptadecanone ((94.5 ± 1.8) kJ mol⁻¹) at T = 298.15 K and the fusion enthalpy of phenyl salicylate (T _fus, 312.7 K, 18.4 ± 0.5) kJ mol⁻¹) were also determined for the correlations. The crystal structure of 1 was determined by X-ray crystallography. Compound 1 exists entirely in the enol form and resembles the crystal structure found for benzoylacetone.     

Thermodynamic properties of the molecular complexes of C<Subscript>60</Subscript>with monosubstituted naphthalenes

Summary The binary systems of C₆₀with α-methyl- and α-chloronaphthalene have been studied by means of differential scanning calorimetry. C₆₀was found to form the molecular complex of the van der Waals type with α-methylnaphthalene which melts incongruently below the boiling point of the solvent at temperature 382.7±3.0 K. The enthalpy of the desolvation reaction is 14.1±0.5 kJ mol^-1of C₆₀. The molar ratio of fullerene to solvent in the solvate is 1:1.5. In the system C₆₀-α-chloronaphthalene a two-stage incongruent melting process has been observed at temperatures 314.1±4.6 K and 375.7±7.4 K with the enthalpies 8.1±2.6 kJ mol^-1and 11.6±1.0 kJ mol^-1, respectively. The composition of the most solvated phase equilibrated with the saturated solution at room temperature and below the first of the incongruent melting transitions was determined as 1:1.5. Based on the results obtained the thermodynamic characteristics of the incongruent melting reactions have been revealed and influence of solvate formation on solubility of C₆₀has been discussed.     

Low-temperature heat capacity and standard enthalpy of formation of neodymium glycine perchlorate complex [Nd2(Gly)6(H2O)4](ClO4)6·5H2O

Rare-earth perchlorate complex coordinated with glycine [Nd₂(Gly)₆(H₂O)₄](ClO₄)₆·5H₂O was synthesized and its structure was characterized by using thermogravimetric analysis (TG), differential thermal analysis (DTA), chemical analysis and elementary analysis. Its purity was 99.90%. Heat capacity measurement was carried out with a high-precision fully-automatic adiabatic calorimeter over the temperature range from 78 to 369 K. A solid-solid phase transformation peak was observed at 256.97 K, with the enthalpy and entropy of the phase transformation process are 4.438 kJ mol⁻¹ and 17.270 J K⁻¹ mol⁻¹, respectively. There is a big dehydrated peak appears at 330 K, its decomposition temperature, decomposition enthalpy and entropy are 320.606 K, 41.364 kJ mol⁻¹ and 129.018 J K⁻¹ mol⁻¹, respectively. The polynomial equations of heat capacity of this compound in different temperature ranges have been fitted. The standard enthalpy of formation was determined to be −8023.002 kJ mol⁻¹ with isoperibol reaction calorimeter at 298.15 K.     

Thermochemistry of the binary system nitrocellulose+2,4-dinitrotoluene

Melting enthalpy and mixing enthalpy of binary system 2,4-dinitrotoluene and nitrocellulose were determined by DSC method. The maximum value of mixing enthalpy was H _max ^M=1.38 kJ mol⁻¹ for molar fraction x _w24DNT = 0.501. The Flory-Huggins parameter (c) was estimated. The solubility curves and glass transition temperatures were predicted and compared with the experimental results. The measurements were performed for the samples with different times of storage at room temperature. The analysis of melting peaks for the mixture leads to the conclusion that for the long periods of storage the melting of 2,4-dinitrotoluene takes place in the confined spaces (pores) and unconfined space (bulk). The crystallization and melting is observed during the short time of storage in mixtures with low nitrocellulose content and in the case of mixtures with a large amount of NC the glass transition is additionally observed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Thermodynamic study of the SOLID-LIQUID equilibria in the MIPO3-Cu(PO3)2 systems

Thermodynamic exploration of solid-liquid equilibria of the M^IPO₃-Cu(PO₃)₂ (with MI=Li, Na, K, Rb, Cs, Ag, Tl) systems is carried out with a semi-empirical equation of the liquidus curves. The enthalpies of fusion of pure polyphosphates and some intermediate compounds were determined from DTA curves. The temperature, enthalpy and entropy of fusion are calculated for each solid phase with the exception of silver polyphosphate and the intermediate compound Cs₄Cu(PO₃)₆ which have very limited crystallization fields. The calculated values of the melting enthalpies are approximately equal to the measured ones. The melting enthalpy of Cu(PO₃)₂ calculated from different binary systems shows a wide variation in the obtained values, 35-54 kJ mol^-1. The experimental value is 33.65 kJ mol^-1. The calculated temperatures and compositions in most binary systems are in good agreement with experimental determinations. This revised version was published online in July 2006 with corrections to the Cover Date.