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1.
The mean apparent molar volume of cyclohexylsulfamic acid has been determined from the density data of aqueous solutions up
to a molality of 0.540 mol⋅kg−1 and at 293.15, 298.15, 303.15, 313.15, and 323.15 K. The mean apparent molar volume of the acid was divided into contributing
ionic and molecular apparent molar volumes. The limiting apparent molar volume of the molecular acid amounts to (131.69± 0.02)
cm3⋅mol−1 and the limiting apparent molar expansibility to (0.130± 0.003) cm3⋅mol−1⋅K−1 at 298.15 K. From the limiting ionic and molecular apparent molar volumes the limiting volume change of ionization of cyclohexylsulfamic
acid was calculated. A value of −7.76 cm3⋅mol−1 was evaluated at 298.15 K. The temperature dependence of the volume change of ionization amounts to −(0.018± 0.009) cm3⋅mol−1⋅K−1. From the density data the coefficient of thermal expansion of the investigated solutions was calculated and from this the
mean apparent molar expansibility of cyclohexylsulfamic acid was derived. 相似文献
2.
The solubility of biphenyl in water at 298.2 K was measured at pressures up to 200 MPa. The logarithm of the solubility linearly
decreased with increasing pressure. From the value of the slope, the volume change for the dissolution of biphenyl in water
was thermodynamically estimated to be 11.8±0.5 cm3⋅mol−1. The solution density of biphenyl in carbon tetrachloride at 298.2 K and 0.10 MPa was also measured to estimate the partial
molar volume of the solute. Using these values and the molar volume of solid biphenyl, the volume change for the hydrophobic
hydration of the biphenyl was estimated to be −6.5±1.6 cm3⋅mol−1. The value was compared with those of methylene group and other aromatic hydrocarbons as a function of the rotational molecular
diameter of these hydrophobic solutes. 相似文献
3.
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
4.
Raphael da C. Cruz Rosana J. Martins Márcio J. E. de M. Cardoso Oswaldo E. Barcia 《Journal of solution chemistry》2009,38(8):957-981
Density measurements were made for binary aqueous solutions of polyethylene glycol at seven temperatures: 283.15, 288.15,
293.15, 298.15, 303.15, 308.15, and 313.15 K. Polyethylene glycol samples with nominal average molar masses of 3000 g⋅mol−1 (PEG 3000), 6000 g⋅mol−1 (PEG 6000), 10000 g⋅mol−1 (PEG 10000) and 20000 g⋅mol−1 (PEG 20000) were used. These results were used to determine the specific volumes of solutions with solute-to-solvent mass
ratios (mass of the solute/mass of the solvent) in the range 0.0546 to 1.4932 for PEG 3000, from 0.0553 to 1.4986 for PEG
6000, from 0.0552 to 1.2241 for PEG 10000, and from 0.0530 to 1.2264 for PEG 20000. The differences between the specific volume
of a solution and the specific volume of the pure solvent, at a given temperature, were represented by a virial-type equation
in terms of solute concentration. The first-order coefficient of the expansion is the partial specific volume of the solute
at infinite dilution. The higher-order coefficients are related to the contribution of pairs, triplets, and higher-order solute
aggregates, according to the Constant-Pressure Solution Theory. The functional dependence of the virial coefficients upon
temperature is discussed in terms of solute-solute and solute-solvent interactions. The effect of the PEG molar mass on the
partial specific volume of solute at infinite dilution, as well as the contributions of pairs of solute molecules to the solution
volume, are also investigated. The apparent specific volume, apparent specific expansibility, apparent specific expansibility
at infinite dilution and virial coefficients of the apparent specific expansibility are also presented. 相似文献
5.
J. Leitner M. Hampl K. Růžička M. Straka D. Sedmidubský P. Svoboda 《Journal of Thermal Analysis and Calorimetry》2008,91(3):985-990
The heat capacity and the enthalpy increments of strontium metaniobate SrNb2O6 were measured by the relaxation method (2-276 K), micro DSC calorimetry (260-320 K) and drop calorimetry (723-1472 K). Temperature
dependence of the molar heat capacity in the form C
pm=(200.47±5.51)+(0.02937±0.0760)T-(3.4728±0.3115)·106/T
2 J K−1 mol−1 (298-1500 K) was derived by the least-squares method from the experimental data. Furthermore, the standard molar entropy
at 298.15 K S
m0 (298.15 K)=173.88±0.39 J K−1 mol−1 was evaluated from the low temperature heat capacity measurements. The standard enthalpy of formation Δf
H
0 (298.15 K)=-2826.78 kJ mol−1 was derived from total energies obtained by full potential LAPW electronic structure calculations within density functional
theory. 相似文献
6.
Stefan Perişanu Iulia Contineanu Mircea D. Banciu Hui Zhao Nigam Rath James Chickos 《Structural chemistry》2006,17(6):639-648
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. 相似文献
7.
N. D. Shikina A. B. Zotov B. R. Tagirov 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2010,84(6):1076-1078
The influence of pressure on the dissociation of arsenous acid H3AsO3 was studied at 298.15 K by the potentiometric method. In the pressure interval from 0.1 to 100 MPa the values of logK
1o = −9.32 + 0.00246P. The change in the molar volume of the reaction of the dissociation of H3AsO3 from the first step (ΔV
1o = −15.4 ± 1 cm3/mol) and the partial molar volume of its dissociation product, H2AsO3− (V
o = 32.1 ± 1 cm3/mol) were determined. 相似文献
8.
J. Leitner K. Růžička D. Sedmidubský P. Svoboda 《Journal of Thermal Analysis and Calorimetry》2009,95(2):397-402
Heat capacity and enthalpy increments of calcium niobates CaNb2O6 and Ca2Nb2O7 were measured by the relaxation time method (2–300 K), DSC (260–360 K) and drop calorimetry (669–1421 K). Temperature dependencies
of the molar heat capacity in the form C
pm=200.4+0.03432T−3.450·106/T
2 J K−1 mol−1 for CaNb2O6 and C
pm=257.2+0.03621T−4.435·106/T
2 J K−1 mol−1 for Ca2Nb2O7 were derived by the least-squares method from the experimental data. The molar entropies at 298.15 K, S
m0(CaNb2O6, 298.15 K)=167.3±0.9 J K−1 mol−1 and S
m0(Ca2Nb2O7, 298.15 K)=212.4±1.2 J K−1 mol−1, were evaluated from the low temperature heat capacity measurements. Standard enthalpies of formation at 298.15 K were derived
using published values of Gibbs energy of formation and presented heat capacity and entropy data: Δf
H
0(CaNb2O6, 298.15 K)= −2664.52 kJ molt-1 and Δf
H
0(Ca2Nb2O7, 298.15 K)= −3346.91 kJ mol−1. 相似文献
9.
J. N. Zhang Z. C. Tan Q. F. Meng Q. Shi B. Tong S. X. Wang 《Journal of Thermal Analysis and Calorimetry》2009,95(2):461-467
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 (Δfus
H
m0), and the molar entropy (Δfus
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 Δc
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, Δr
H
m0 (C6H8N2,cr)= −1.74±0.57 kJ mol−1. 相似文献
10.
The vaporization enthalpies and liquid vapor pressures from T = 298.15 K to T = 400 K of 1,3,5-triazine, pyrazine, pyrimidine, and pyridazine using pyridines and pyrazines as standards have been measured
by correlation-gas chromatography. The vaporization enthalpies of 1,3,5-triazine (38.8 ± 1.9 kJ mol−1) and pyrazine (40.5 ± 1.7 kJ mol−1) obtained by these correlations are in good agreement with current literature values. The value obtained for pyrimidine (41.0 ± 1.9 kJ mol−1) can be compared with a literature value of 50.0 kJ mol−1. Combined with the condensed phase enthalpy of formation in the literature, this results in a gas-phase enthalpy of formation,
Δf
H
m (g, 298.15 K), of 187.6 ± 2.2 kJ mol−1 for pyrimidine, compared to a value of 195.1 ± 2.1 calculated for pyrazine. Vapor pressures also obtained by correlation
are used to predict boiling temperatures (BT). Good agreement with experimental BT (±4.2 K) including results for pyrimidine
is observed for most compounds with the exception of the pyridazines. The results suggest that compounds containing one or
two nitrogen atoms in the ring are suitable standards for correlating various heterocyclic compounds provided the nitrogen
atoms are isolated from each other by carbon. Pyridazines do not appear to be evaluated correctly using pyridines and pyrazines
as standards. 相似文献
11.
Manuel A. V. Ribeiro da Silva Luísa M. P. F. Amaral 《Journal of Thermal Analysis and Calorimetry》2010,100(2):375-380
The standard (p
o = 0.1 MPa) molar enthalpies of formation
\Updelta\textf H\textm\texto ( \textl), {{\Updelta}}_{\text{f}} H_{\text{m}}^{\text{o}} ( {\text{l),}} of the liquid 2-methylfuran, 5-methyl-2-acetylfuran and 5-methyl-2-furaldehyde were derived from the standard molar energies
of combustion, in oxygen, at T = 298.15 K, measured by static bomb combustion calorimetry. The Calvet high temperature vacuum sublimation technique was
used to measure the enthalpies of vaporization of the three compounds. The standard (p
o = 0.1 MPa) molar enthalpies of formation of the compounds, in the gaseous phase, at T = 298.15 K have been derived from the corresponding standard molar enthalpies of formation in the liquid phase and the standard
molar enthalpies of vaporization. The results obtained were −(76.4 ± 1.2), −(253.9 ± 1.9), and −(196.8 ± 1.8) kJ mol−1, for 2-methylfuran, 5-methyl-2-acetylfuran, and 5-methyl-2-furaldehyde, respectively. 相似文献
12.
E. V. Ivanov V. K. Abrosimov N. G. Ivanova E. Yu. Lebedeva 《Russian Chemical Bulletin》2007,56(10):1996-1999
The densities of aqueous solutions of bisurea (2,4,6,8-tetraazabicyclo[3.3.0]octane-3,7-dione) were measured using a vibrating-tube
densimeter at 288.15, 298.15, 308.15, and 318.15 K in the concentration range up to ∼3·10−3 moles of solute (1000 g of H2O)−1 with the error at most ±5· 10−6 g cm−3 (reproducibility up to 2·10−6 g cm−3). The limiting partial molar volume and expansibility of bisurea in water were calculated. The bicyclic molecules under study
form in aqueous solution H-bonded hydrate complexes with rather high structure-packing density. These complexes are more subjected
to the destroying effect of temperature than the corresponding urea complexes. The hydration of bisurea weakens with the temperature
increase.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1929–1932, October, 2007. 相似文献
13.
Densities, ρ, and speed of sound, u for glycine, L-alanine and L-valine in (0.2, 0.4, 0.6, and 0.8) mol · kg−1 aqueous solutions of trisodium citrate at T = (288.15, 298.15, 308.15 and 318.15) K have been measured. The different parameters such as apparent molar volume, limiting apparent molar volume, transfer volume, have been derived from density data. Experimental values of the speed of sound were used to estimate apparent molar apparent molar isentropic compression, limiting apparent molar isentropic compression, and transfer parameter. The pair and triplet interaction coefficient have been calculated from transfer parameters. 相似文献
14.
Liang Xue Feng-Qi Zhao Xiao-Ling Xing Zhi-Ming Zhou Kai Wang Hong-Xu Gao Jian-Hua Yi Rong-Zu Hu 《Journal of Thermal Analysis and Calorimetry》2010,102(3):989-992
The thermal decomposition behavior of 3,4,5-triamino-1,2,4-triazole dinitramide was measured using a C-500 type Calvet microcalorimeter
at four different temperatures under atmospheric pressure. The apparent activation energy and pre-exponential factor of the
exothermic decomposition reaction are 165.57 kJ mol−1 and 1018.04 s−1, respectively. The critical temperature of thermal explosion is 431.71 K. The entropy of activation (ΔS
≠), enthalpy of activation (ΔH
≠), and free energy of activation (ΔG
≠) are 97.19 J mol−1 K−1, 161.90 kJ mol−1, and 118.98 kJ mol−1, respectively. The self-accelerating decomposition temperature (T
SADT) is 422.28 K. The specific heat capacity of 3,4,5-triamino-1,2,4-triazole dinitramide was determined with a micro-DSC method
and a theoretical calculation method. Specific heat capacity (J g−1 K−1) equation is C
p = 0.252 + 3.131 × 10−3
T (283.1 K < T < 353.2 K). The molar heat capacity of 3,4,5-triamino-1,2,4-triazole dinitramide is 264.52 J mol−1 K−1 at 298.15 K. The adiabatic time-to-explosion of 3,4,5-triamino-1,2,4-triazole dinitramide is calculated to be a certain value
between 123.36 and 128.56 s. 相似文献
15.
Silvia Castrignanò Sheila J. Sadeghi Gianfranco Gilardi 《Analytical and bioanalytical chemistry》2010,398(3):1403-1409
Human flavin-containing monooxygenases are the second most important class of drug-metabolizing enzymes after cytochromes
P450. Here we report a simple but functional and stable enzyme-electrode system based on a glassy carbon (GC) electrode with
human flavin-containing monooxygenase isoform 3 (hFMO3) entrapped in a gel cross-linked with bovine serum albumin (BSA) by
glutaraldehyde. The enzymatic electrochemical responsiveness is characterised by using well-known substrates: trimethylamine
(TMA), ammonia (NH3), triethylamine (TEA), and benzydamine (BZD). The apparent Michaelis–Menten constant (K′M) and apparent maximum current (I′max) are calculated by fitting the current signal to the Michaelis–Menten equation for each substrate. The enzyme-electrode has
good characteristics: the calculated sensitivity was 40.9 ± 0.5 mA mol−1 L cm−2 for TMA, 43.3 ± 0.1 mA mol−1 L cm−2 for NH3, 45.2 ± 2.2 mA mol−1 L cm−2 for TEA, and 39.3 ± 0.6 mA mol−1 L cm−2 for BZD. The stability was constant for 3 days and the inter-electrode reproducibility was 12.5%. This is a novel electrochemical
tool that can be used to investigate new potential drugs against the catalytic activity of hFMO3. 相似文献
16.
Lebedev B. V. Bykova T. A. Lobach A. S. 《Journal of Thermal Analysis and Calorimetry》2000,62(1):257-265
The temperature dependence of the molar heat capacity (C0
p) of hydrofullerene C60H36 between 5 and 340 K was determined by adiabatic vacuum calorimetry with an error of about 0.2%. The experimental data were
used for the calculation of the thermodynamic functions of the compound in the range 0 to340 K. It was found that at T=298.15 K and p=101.325 kPa C0
p (298.15)=690.0 J K−1 mol−1,Ho(298.15)−Ho(0)= 84.94 kJ mol−1,So(298.15)=506.8 J K−1 mol−1, Go(298.15)−Ho(0)= −66.17 kJ mol−1. The standard entropy of formation of hydrofullerene C60H36 and the entropy of reaction of its formation by hydrogenation of fullerene C60 with hydrogen were estimated and at T=298.15 K they were ΔfSo= −2188.4 J K−1 mol−1 and ΔrSo= −2270.5 J K−1mol−1, respectively.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
17.
B. Tong Z. C. Tan J. N. Zhang S. X. Wang 《Journal of Thermal Analysis and Calorimetry》2009,95(2):469-475
The low-temperature heat capacity C
p,m of erythritol (C4H10O4, CAS 149-32-6) was precisely measured in the temperature range from 80 to 410 K by means of a small sample automated adiabatic
calorimeter. A solid-liquid phase transition was found at T=390.254 K from the experimental C
p-T curve. The molar enthalpy and entropy of this transition were determined to be 37.92±0.19 kJ mol−1 and 97.17±0.49 J K−1 mol−1, respectively. The thermodynamic functions [H
T-H
298.15] and [S
T-S
298.15], were derived from the heat capacity data in the temperature range of 80 to 410 K with an interval of 5 K. The standard
molar enthalpy of combustion and the standard molar enthalpy of formation of the compound have been determined: Δc
H
m0(C4H10O4, cr)= −2102.90±1.56 kJ mol−1 and Δf
H
m0(C4H10O4, cr)= − 900.29±0.84 kJ mol−1, by means of a precision oxygen-bomb combustion calorimeter at T=298.15 K. DSC and TG measurements were performed to study the thermostability of the compound. The results were in agreement
with those obtained from heat capacity measurements. 相似文献
18.
Kang-Zhen Xu Yong-Shun Chen Min Wang Jin-An Luo Ji-Rong Song Feng-Qi Zhao Rong-Zu Hu 《Journal of Thermal Analysis and Calorimetry》2011,105(1):293-300
A novel energetic material, 4,5-dihydroxyl-2-(dinitromethylene)-imidazolidine (DDNI), was synthesized by the reaction of FOX-7
and glyoxal in water at 70 °C. Thermal behavior of DDNI was studied with DSC and TG-DTG methods, and presents only an intense
exothermic decomposition process. The apparent activation energy and pre-exponential factor of the decomposition reaction
were 286.0 kJ mol−1 and 1031.16 s−1, respectively. The critical temperature of thermal explosion of DDNI is 183.78 °C. Specific heat capacity of DDNI was studied
with micro-DSC method and theoretical calculation method, and the molar heat capacity is 217.76 J mol−1 K−1 at 298.15 K. The adiabatic time-to-explosion was also calculated to be a certain value between 14.54 and 16.34 s. DDNI presents
lower thermal stability, for its two ortho-hydroxyl groups, and its thermal decomposition process becomes quite intense. 相似文献
19.
A. G. Ramazanova V. I. Yashkova O. V. Balmasova V. V. Korolev E. V. Ivanov 《Russian Chemical Bulletin》2006,55(4):666-671
Densities of solutions of oleic, linoleic, and linolenic acids in n-hexane and n-heptane were measured using a vibrating-tube densimeter at 298.15 K in a concentration range of 0–0.012 molar fractions of
solute. The measurement error does not exceed ±5·10−6 g cm−3. The limiting partial molar volumes of fatty acids of the studied series in n-hexane and n-heptane and the excess volume properties of binary mixtures were calculated. On going from oleic to linolenic acid, the number
of double bonds (>C=C<) in a solute molecule increases, the hydrocarbon chain length in a solvent molecule decreases, and
compactness of the structure packing of the resulting solution increases. This is caused, as a whole, by the enhancement of
the n-alkane—acid intermolecular interaction.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 643–647, April, 2006. 相似文献
20.
Y. Xu-Wu Z. Hang-Guo S. Wu-Juan W. Xiao-Yan G. Sheng-Li 《Journal of Thermal Analysis and Calorimetry》2008,92(3):961-965
The copper(II) complex of 6-benzylaminopurine (6-BAP) has been prepared with dihydrated cupric chloride and 6-benzylaminopurine.
Infrared spectrum and thermal stabilities of the solid complex have been discussed. The constant-volume combustion energy,
Δc
U, has been determined as −12566.92±6.44 kJ mol−1 by a precise rotating-bomb calorimeter at 298.15 K. From the results and other auxiliary quantities, the standard molar enthalpy
of combustion, Δc
H
m
θ, and the standard molar of formation of the complex, Δf
H
m
θ, were calculated as −12558.24±6.44 and −842.50±6.47 kJ mol−1, respectively. 相似文献