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1.
The enthalpy of mixing of formamide,N-methylformamide,N,N-dimethylformamide, and hexamethylphosphoric triamide with MeCN was measured in the 283–328 K range. The enthalpic coefficients
of the binary and ternary interactions between the amide molecules are calculated within the framework of the McMillan-Mayer
theory. The contributions to the enthalpy of dissolution due to cavity formation in the solvent (Δcav
H
0) and due to solute-solvent interaction (Δint
H
0) were determined. The enthalpies of specific and nonspecific solvation of amides in MeCN were calculated. The main contribution
to the enthalpy of solvation of formamide andN-methylformamide is from specific interactions, while forN,N-dimethylformamide and hexamethylphosphoric triamide it is from nonspecific interactions. The values obtained are compared
with those for solutions of the amides mentioned in water and methanol.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1730–1735, October, 1993. 相似文献
2.
M. Slavík J. Šedlbauer K. Ballerat-Busserolles V. Majer 《Journal of solution chemistry》2007,36(1):107-134
The heat capacities of aqueous solutions of acetone, 2,5-hexanedione, diethyl ether, 1,2-dimethoxyethane, benzyl alcohol and
cyclohexanol at concentrations of 0.1 to 1.0 mol⋅kg−1 were determined at temperatures of 298.15, 423.15, 473.15 and 523.15 K and pressures up to 28 MPa. The measurements were
performed at ambient conditions using the commercial Picker differential flow calorimeter and at high temperatures and pressures
with a customized Picker type calorimeter constructed at the Blaise Pascal University, Clermont-Ferrand. Standard molar heat
capacities were obtained by weighted extrapolation to the infinite dilution limit. The contributions of –CO–, –O– and –OH
groups to the standard molar volume and standard molar heat capacity were determined from the newly determined and literature
data. The variation of the three oxygen-containing group contributions with temperature and molecular structure is examined
qualitatively. 相似文献
3.
The enthalpies of mixing ofN,N-dialkylpropionamides with water were measured at 298.15 K. A comparative analysis of enthalpy effects (H
E) of mixing of water withN,N-disubstituted amides of formic, acetic, and propionic acids was performed. It was established that theH
E values depend on the length of theN,N-alkyl substituents and the size of acidic radicals. The size of the nonpolar group and the electron-donor ability of amide
molecules primarily affect the enthalpy of mixing. The relative electron-donor abilities of the amides were estimated by the
calorimetric method. The results obtained were discussed by invoking thermochemical data for aqueous solutions of hexamethylphosphoric
triamide.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1805–1810, October, 1997. 相似文献
4.
M. V. Kulikov 《Russian Chemical Bulletin》1997,46(2):274-278
The enthalpies of mixing of acetonitrile with formamide,N-methylformamide,N,N-dimethylformamide, and hexamethylphosphoric triamide were measured in the temperature interval from 283.15 to 328.15 K. The
enthalpy coefficients of binary and ternary interactions were calculated by the methods of the McMillan-Mayer theory. The
contributions to the enthalpy of solution due to the formation of a cavity in the solvent, Δcav
H°, and those due to the interaction of the solute with the solvent, Δint
H°, were determined. The enthalpies of the specific and non-specific solvation of acetonitrile in the corresponding amides
were calculated. Specific interactions were found to contribute the most to the solvation enthalpy of acetonitrile. The obtained
values were compared with analogous values for solutions of acetonitrile in water and alcohols.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 289–293, February, 1997. 相似文献
5.
A. V. Kustov 《Russian Journal of Inorganic Chemistry》2011,56(5):824-829
The heats of solution of tetrahexylammonium and tetraheptylammonium bromides in water and aqueous solutions of formamide and
hexamethylphosphoric triamide have been measured at 318 and 338 K. The standard enthalpies and heat capacities of solution
and the enthalpic and heart capacity parameters of amide-electrolyte pair interaction have been determined. It has been confirmed
that the standard heat capacities of solution and the amide-electrolyte interaction parameters as a function of the cation
size pass through an extremum. The hydrophobic hydration effect is weaker for large tetraalkylammonium cations. 相似文献
6.
Qing-Fen Meng Zhi-Cheng Tan Ya-Ping Dong Hai-Tao Feng Xiao-Huan Wang Quan Shi Wu Li 《Journal of solution chemistry》2010,39(7):1087-1098
The molar heat capacities of three different concentrations of aqueous SrCl2 solutions, 0.1212, 0.4615 and 1.878 mol⋅kg−1, were measured, using a precision automated adiabatic calorimeter in the temperature range from 80 to 320 K. Solid–liquid
phase transitions were observed at 272.83, 270.18 and 255.15 K, respectively, for these three solutions. The molar enthalpies
and entropies of the phase transitions were evaluated. The experimental heat capacity data were fitted to polynomial equations,
and based on the polynomial equations and thermodynamic relationship, the thermodynamic functions relative to 298.15 K, [H
T
−H
298.15 K] and [S
T
−S
298.15 K], of the three solutions were derived in the range of 80 to 320 K with an interval of 5 K. 相似文献
7.
Ultrasonic velocity and density values are measured for aqueous solutions containing 2.00 mol.%, 4.00 mol.%, and 5.00 mol.%
glycine in a temperature range of 15–65°C, 5.50 mol.% glycine (20–65°C), and 6.00 mol.% glycine (25–65°C). Adiabatic compressibilities
(κS) and molar adiabatic compressibilities (KS) are calculated. The values of κS and KS decrease monotonically with an increase in glycine concentrations up to saturation at all the temperatures. The temperature
dependences of κS and κS have minima that are typical of water and aqueous solutions; the positions of the minima depend on the glycine concentration.
The temperature coefficients of the molar compressibility, ∂KS/∂T, change their signs from negative to positive at lower temperatures (by approximately 10 deg) than ∂κS/∂T. 相似文献
8.
Preparation and characterization of anion-cation surfactants modified montmorillonite 总被引:3,自引:2,他引:1
D. Chen J. X. Zhu P. Yuan S. J. Yang T. -H. Chen H. P. He 《Journal of Thermal Analysis and Calorimetry》2008,94(3):841-848
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. 相似文献
9.
M. N. Rodnikova M. A. Gunina D. M. Makarov G. I. Egorov T. M. Val’kovskaya 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2011,85(9):1676-1678
The densities of ethylene glycol solutions of tetrahydrofuran (THF) with 0–20 mol % THF were measured at 20–60°C and atmospheric
pressure to an accuracy of 5 × 10−5 g/cm3. The apparent molar volumes of THF in the solutions were calculated and their concentration and temperature dependences determined.
The results were compared with the apparent molar volumes of THF in aqueous systems calculated from the literature data. Minima
were found on the concentration dependence of the apparent volume of THF for both aqueous and ethylene glycol solutions and
changed differently as the temperature increased. The data obtained were discussed from the standpoint of solvophobic effects
in aqueous and ethylene glycol solutions of THF. 相似文献
10.
M. Hampl J. Leitner K. Růžička M. Straka P. Svoboda 《Journal of Thermal Analysis and Calorimetry》2007,87(2):553-556
The heat capacity and the heat content of
bismuth niobate BiNb5O14 were
measured by the relaxation time method, DSC and drop method, respectively.
The temperature dependence of heat capacity in the form C
pm=455.84+0.06016T–7.7342·106/T
2 (J K–1
mol–1) was derived by the least squares method
from the experimental data. Furthermore, the standard molar entropy at 298.15
K S
m=397.17 J K–1
mol–1 was derived from the low temperature
heat capacity measurement. 相似文献
11.
Hung-Wei Tsui Jing-Han Wang Ya-Hui Hsu Li-Jen Chen 《Colloid and polymer science》2010,288(18):1687-1696
Heat of micellization and phase separation temperature (known as cloud point) for the poly(ethylene oxide)–poly(propylene
oxide)–poly(ethylene oxide) (abbreviated by PEO–PPO–PEO) triblock copolymers, the Pluronics F108, F98, F88, F68, F38, P65,
and L62, in water are carefully determined by using a high sensitivity differential scanning calorimeter. It is interesting
to find out that there exists a maximum heat of micellization for all these Pluronics. In this study, the heat of micellization
of all of the Pluronics decreases as the temperature increases, as expected, at high temperature region (low Pluronic concentration
region). However, the enthalpy change has a surprisingly positive relationship with temperature at low temperature region
(high Pluronic concentration region). The critical micelle temperature consistently decreases as the Pluronic concentration
increases. This unexpected behavior of the positive heat capacity changes of Pluronic aqueous solutions at higher concentration
region is somewhat related to the variation of water accessible polar (PEO groups) and non-polar (PPO groups) surface areas
in the micellization process. Especially, the removal of polar surface area from water may dominate the contribution to the
positive heat capacity change upon micellization. In addition, the cloud points of Pluronic solutions are also discussed.
The enthalpy–entropy compensation phenomenon for the micellization of Pluronics is discussed, and the enthalpy–entropy compensation
temperature is calculated. 相似文献
12.
Experimental molar heat capacity data (Cp
m) and excess molar heat capacity data (CpEm\mathit{Cp}^{\mathrm{E}}_{\mathrm{m}}) of binary mixtures containing water + (formamide or N,N-dimethylformamide or dimethylsulfoxide or N,N-dimethylacetamide
or 1,4-dioxane) at several compositions, in the temperature range 288.15 K to 303.15 K and atmospheric pressure, have been
determined using a modified 1455 PAAR solution calorimeter. The excess heat capacities are positive for aqueous solutions
containing 1,4-dioxane, N,N-dimethylformamide or dimethylsulfoxide, negative for solutions containing water + formamide and
show a sigmoid behavior for mixtures containing water + N,N-dimethylacetamide, over the whole composition range. The experimental
excess molar heat capacities are discussed in terms of the influence of temperature and of the organic solvent type present
in the binary aqueous mixtures, as well as in terms of the existing molecular interactions and the organic solvent’s molecular
size and structure. 相似文献
13.
14.
The molar heat capacities of the binary mixture
composed of water and n-butanol were measured with an adiabatic calorimeter
in the temperature range 78–320 K. The functions of the heat capacity
with respect to thermodynamic temperature were established. A glass transition,
solid–solid phase transition and solid–liquid phase transition
were observed. The corresponding enthalpy and entropy of the solid–liquid
phase transition were calculated, respectively. The thermodynamic functions
relative to a temperature of 298.15 K were derived based on the relationships
of the thermodynamic functions and the function of the measured heat capacity
with respect to temperature. 相似文献
15.
Y. Asai 《Colloid and polymer science》2001,279(11):1134-1138
The purpose of this study was to develop an intravenous formulation composed of vitamin K1 (VK) for the treatment of blood coagulation with warfarin-induced hypoprothrombinaemia. VK was dispersed using sonication
with soybean phosphatidylcholine (PC) and the dispersion mechanism was evaluated by characterizing the dispersed particles
with dynamic light scattering, fluorescence spectroscopy and surface monolayer techniques. VK has an appreciable solubility
in PC bilayers (approximately 20 mol%). Within the VK molar fraction of 0.1–0.9, the size of the dispersed particles increased
at room temperature within 3 months. By addition of soybean oil (SO) to VK (molar ratio of VK:SO=1:1), the solubility of the
VK/SO mixtures in PC bilayers was decreased (approximately 5 mol%). The size of the aqueous dispersions at molar fractions
of 0.1–0.7 was 50–70 nm and did not change for 3 months at room temperature. The solubility of the VK and VK/SO in PC bilayers
is crucially important in the production of the stable aqueous dispersions of VK particles.
Received: 1 August 2000 Accepted: 20 December 2000 相似文献
16.
The electrical conductivities of aqueous solutions of quinic acid and its sodium salt were measured from 293.15 to 328.15 K
in steps of 5 K. The molar conductivities of the sodium salt were treated by the Lee–Wheaton equation, in the form of Pethybridge
and Taba, and the Kohlrausch equations. The limiting molar conductivities of the quinate anion were estimated, as well as
the corresponding ionic association constants and standard thermodynamic functions of the ionic association reaction. The
hydrodynamic radius of the quinate anion was calculated from the Walden rule and compared with the van der Waals radius. The
dissociation constant of quinic acid was evaluated from the known value of the limiting molar conductivity of quinic acid
using the conductivity equation of Pethybridge and Taba. The standard thermodynamic functions of the dissociation process,
i.e., the Gibbs energy, enthalpy, entropy and heat capacity, were obtained using the non-empirical procedure given by Clarke
and Glew. The standard thermodynamic functions of dissociation of quinic acid are discussed in terms of solute–solvent interactions
and stabilization of the quinate anion due to hydrogen bonding of the α-hydroxyl group to the carboxyl group. 相似文献
17.
The viscosity of 10 (0.049, 0.205, 0.464, 0.564, 0.820, 1.105, 1.496, 2.007, 2.382, and 2.961 mol ċ kg−1) binary aqueous NaBr solutions has been measured with a capillary-flow technique. Measurements were made at pressures up to 40 MPa. The range of temperature was 288–595 K. The total uncertainty of viscosity, pressure, temperature and composition measurements were estimated to be less than 1.6%, 0.05%, 15 mK, and 0.02%, respectively. The effect of temperature, pressure, and concentration on viscosity of binary aqueous NaBr solutions were studied. The measured values of the viscosity of NaBr(aq) were compared with data, predictions and correlations reported in the literature. The temperature and pressure coefficients of viscosity of NaBr(aq) were studied as a function of concentration and temperature. The viscosity data have been interpreted in terms of the extended Jones–Dole equation for the relative viscosity (η/η0) to calculate accurately the values of viscosity A- and B-coefficients as a function of temperature. The derived values of the viscosity A- and B-coefficients were compared with the results predicted by the Falkenhagen–Dole theory of electrolyte solutions and calculated with the ionic B-coefficient data. The physical meaning parameters V and E in the absolute rate theory of the viscosity and hydrodynamic molar volume V
k were calculated using the present experimental viscosity data. The TTG model has been used to compare predicted values of the viscosity of NaBr(aq) solutions with experimental values at high pressures. 相似文献
18.
V. P. Korolev O. A. Antonova N. L. Smirnova 《Journal of Thermal Analysis and Calorimetry》2012,108(1):1-7
The enthalpies of solution of l-proline have been measured in aqueous urea solutions at 0–6 mol urea kg−1 water at 288.15, 298.15, 308.15, and 318.15 K by the calorimetric method. The two-parameter relation connecting the values
of solution enthalpies of proline with urea concentration and temperature has been obtained. The enthalpy and heat capacity
parameters of pair interaction of l-proline with urea in water have been computed. Using the thermodynamic relations, the temperature changes of reduced enthalpy,
and also the change of entropy and reduced Gibbs energy of solution of l-proline in aqueous solutions of urea at the temperature rise from 288 to 318 K have been determined. Their comparison with
the data for glycine and l-alanine has been carried out. It has been shown that the entropy–enthalpy compensation (Barclay–Butler rule) takes place
for dissolution and transfer processes. 相似文献
19.
M.-H. Wang Z.-C. Tan Q. Shi L.-X. Sun T. Zhang 《Journal of Thermal Analysis and Calorimetry》2006,84(2):413-418
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, ΔfusHm,
and entropy, ΔfusSm,
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 (HT–H298.15) and (ST–S298.15) 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. 相似文献
20.
In this paper, the crosslinked polyester resin containing acrylic acid functional groups was used for the adsorption of uranium
ions from aqueous solutions. For this purpose, the crosslinked polyester resin of unsaturated polyester in styrene monomer
(Polipol 353, Poliya) and acrylic acid as weight percentage at 80 and 20%, respectively was synthesized by using methyl ethyl
ketone peroxide (MEKp, Butanox M60, Azo Nobel)-cobalt octoate initiator system. The adsorption of uranium ions on the sample (0.05 g copolymer
and 5 mL of U(VI) solution were mixed) of the crosslinked polyester resin functionalized with acrylic acid was carried out
in a batch reactor. The effects of adsorption parameters of the contact time, temperature, pH of solution and initial uranium(VI)
concentration for U(VI) adsorption on the crosslinked polyester resin functionalized with acrylic acid were investigated.
The adsorption data obtained from experimental results depending on the initial U(VI) concentration were analyzed by the Freundlich,
Langmuir and Dubinin–Radushkevich (D–R) adsorption isotherms. The adsorption capacity and free energy change were determined
by using D–R isotherm. The obtained experimental adsorption data depending on temperature were evaluated to calculate the
thermodynamic parameters of enthalpy (ΔH°), entropy (ΔS°) and free energy change (ΔG°) for the U(VI) adsorption on the crosslinked polyester resin functionalized with acrylic acid from aqueous solutions. The
obtained adsorption data depending on contact time were analyzed by using adsorption models such as the modified Freundlich,
Elovich, pseudo-first order and pseudo-second-order kinetic models. 相似文献