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1.
Polymorphism of paracetamol 总被引:1,自引:0,他引:1
G. L. Perlovich Tatyana V. Volkova Annette Bauer-Brandl 《Journal of Thermal Analysis and Calorimetry》2007,89(3):767-774
The thermodynamic relationship between crystal modifications of paracetamol was studied by alternative methods. Temperature
dependence of saturated vapor pressure for polymorphic modifications of the drug paracetamol (acetaminophen) was mea sured
and thermodynamic functions of the sublimation process calculated. Solution calorimetry was carried out for the two modifications
in the same solvent. Thermodynamic parameters for sublimation for form I (monoclinic) were found: ΔG
sub298=60.0 kJ mol−1; ΔH
sub298=117.9±0.7 kJ mol−1; ΔS
sub298=190±2 J mol−1 K−1. For the orthorhombic modification (form II), the saturated vapor pressure could only be studied at 391 K. Phase transition
enthalpy at 298 K, ΔH
tr298(I→II)=2.0±0.4 kJ mol−1, was derived as the difference between the solution enthalpies of the noted polymorphs in the same solution (methanol). Based
on ΔH
tr298 (I→II), differences between temperature dependencies of heat capacities of both modifications and the vapor pressure value
of form II at 391 K, the temperature dependence of saturated vapor pressure and thermodynamic sublimation parameters for modification
II were also estimated (ΔG
sub298=56.1 kJ mol−1; ΔH
sub298=115.9±0.9 kJ mol−1; ΔS
sub298=200±3 J mol−1 K−1). The results indicate that the modifications are monotropically related, which is in contrast to findings recently reported
found by classical thermochemical methods. 相似文献
2.
M. A. V. Ribeiro da Silva C. P. F. Santos M. J. S. Monte C. A. D. Sousa 《Journal of Thermal Analysis and Calorimetry》2006,83(3):533-539
The
standard (p0=0.1
MPa) molar enthalpies of formation, ΔfHm0, for
crystalline phthalimides: phthalimide, N-ethylphthalimide
and N-propylphthalimide were derived from
the standard molar enthalpies of combustion, in oxygen, at the temperature
298.15 K, measured by static bomb-combustion calorimetry, as, respectively,
– (318.0±1.7), – (350.1±2.7) and – (377.3±2.2)
kJ mol–1. The standard molar enthalpies of
sublimation, ΔcrgHm0, at T=298.15
K were derived by the Clausius-Clapeyron equation, from the temperature dependence
of the vapour pressures for phthalimide, as (106.9±1.2) kJ mol–1
and from high temperature Calvet microcalorimetry for phthalimide, N-ethylphthalimide and N-propylphthalimide
as, respectively, (106.3±1.3), (91.0±1.2) and (98.2±1.4)
kJ mol–1.
The derived standard molar enthalpies of formation,
in the gaseous state, are analysed in terms of enthalpic increments and interpreted
in terms of molecular structure. 相似文献
3.
Z. Fengqi G. Hongxu L. Yang H. Rongzu C. Pei G. Sheng-li Y. Xu-wu S. Qizhen 《Journal of Thermal Analysis and Calorimetry》2006,85(3):791-794
The constant-volume combustion energies of
the lead salts of 2-hydroxy-3,5-dinitropyridine (2HDNPPb) and 4-hydroxy-3,5-dinitropyridine
(4HDNPPb), ΔU
c
(2HDNPPb(s) and 4HDNPP(s)),
were determined as –4441.92±2.43 and –4515.74±1.92
kJ mol–1 , respectively, at 298.15 K. Their
standard enthalpies of combustion, Δc
m
H θ(2HDNPPb(s) and 4HDNPPb(s), 298.15 K), and standard enthalpies of formation,
Δr
m H θ(2HDNPPb(s) and 4HDNPPb(s),
298.15 K) were as –4425.81±2.43, –4499.63±1.92 kJ
mol–1 and –870.43±2.76, –796.65±2.32
kJ mol–1 , respectively. As two combustion
catalysts, 2HDNPPb and 4HDNPPb can enhance the burning rate and reduce the
pressure exponent of RDX–CMDB propellant. 相似文献
4.
M. A. V. Ribeiro da Silva Cláudia P. F. Santos 《Journal of Thermal Analysis and Calorimetry》2007,87(1):21-25
The standard (p
0=0.1
MPa) molar enthalpy of formation, Δf
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, Δg
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. 相似文献
5.
G. Xie S. P. Chen S. L. Gao X. X. Meng Q. Z. Shi 《Journal of Thermal Analysis and Calorimetry》2006,83(3):693-700
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, ΔrHmθ (sol), and the molar heat capacity of the complex, cm,
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, ΔrHmθ(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, ΔcU, 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, ΔcHmθ, and standard enthalpy of formation,
ΔfHmθ, were calculated to be –16803.95±7.74 and –1115.42±8.94
kJ mol–1, respectively. 相似文献
6.
Thermochemical
studies on the thioproline 总被引:3,自引:0,他引:3
The combustion energy of thioproline was determined
by the precision rotating-bomb calorimeter at 298.15 K to be Δc
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 Δc
H
m
θC4H7NO2S,
(s), 298.15 K= –2469.92±1.44 kJ mol–1
and Δf
H
m
θC4H7NO2S, (s), 298.15K= –401.33±1.54
kJ mol–1. 相似文献
7.
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
8.
1. Results of thermodynamic and kinetic investigations for the different crystalline calcium carbonate phases and their phase
transition data are reported and summarized (vaterite: V; aragonite: A; calcite: C). A→C: T
tr=455±10°C, Δtr
H=403±8 J mol–1 at T
tr, V→C: T
tr=320–460°C, depending on the way of preparation,Δtr
H=–3.2±0.1 kJ mol–1 at T
tr,Δtr
H=–3.4±0.9 kJ mol–1 at 40°C, S
V
Θ= 93.6±0.5 J (K mol)–1, A→C: E
A=370±10 kJ mol–1; XRD only, V→C: E
A=250±10 kJ mol–1; thermally activated, iso- and non-isothermal, XRD
2. Preliminary results on the preparation and investigation of inhibitor-free non-crystalline calcium carbonate (NCC) are
presented. NCC→C: T
tr=276±10°C,Δtr
H=–15.0±3 kJ mol–1 at T
tr, T
tr – transition temperature, Δtr
H – transition enthalpy, S
Θ – standard entropy, E
A – activation energy.
3. Biologically formed internal shell of Sepia officinalis seems to be composed of ca 96% aragonite and 4% non-crystalline calcium carbonate.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
9.
I. Zięborak-Tomaszkiewicz 《Journal of Thermal Analysis and Calorimetry》2006,83(3):611-615
The energies of combustion
in fluorine of gallium nitride and indium nitride in wurzite crystalline structure
have been measured in a two-compartment calorimetric bomb, and new standard
molar enthalpies of formation have been calculated: ΔfHm0(GaN(cr)
298.15 K)= –(163.7±4.2) kJ mol–1
and ΔfHm0(InN(cr) 298.15 K)= –(146.5±4.6) kJ mol–1
. Comparison with the recommended values of the ΔfHm0 nitrides
from the literature is also presented. 相似文献
10.
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. 相似文献
11.
S. P. Chen X. X. Meng Q. Shuai B. J. Jiao S. L. Gao Q. Z. Shi 《Journal of Thermal Analysis and Calorimetry》2006,86(3):767-774
A
solid complex Eu(C5H8NS2)3(C12H8N2) has been obtained from reaction of
hydrous europium chloride with ammonium pyrrolidinedithiocarbamate (APDC)
and 1,10-phenanthroline (o-phen⋅H2O)
in absolute ethanol. IR spectrum of the complex indicated that Eu3+
in the complex coordinated with sulfur atoms from the APDC and nitrogen atoms
from the o-phen. TG-DTG investigation provided
the evidence that the title complex was decomposed into EuS.
The
enthalpy change of the reaction of formation of the complex in ethanol, Δr
H
m
θ(l), as –22.214±0.081 kJ mol–1,
and the molar heat capacity of the complex, c
m,
as 61.676±0.651 J mol–1 K–1,
at 298.15 K were determined by an RD-496 III type microcalorimeter. The enthalpy
change of the reaction of formation of the complex in solid, Δr
H
m
θ(s), was calculated as 54.527±0.314 kJ mol–1
through a thermochemistry cycle. Based on the thermodynamics and kinetics
on the reaction of formation of the complex in ethanol at different temperatures,
fundamental parameters, including the activation enthalpy (ΔH
≠
θ),
the activation entropy (ΔS
≠
θ),
the activation free energy (ΔG
≠
θ),
the apparent reaction rate constant (k),
the apparent activation energy (E), the
pre-exponential constant (A) and the reaction
order (n), were obtained. The constant-volume
combustion energy of the complex, Δc
U,
was determined as –16937.88±9.79 kJ mol–1
by an RBC-II type rotating-bomb calorimeter at 298.15 K. Its standard enthalpy
of combustion, Δc
H
m
θ,
and standard enthalpy of formation, Δf
H
m
θ,
were calculated to be –16953.37±9.79 and –1708.23±10.69
kJ mol–1, respectively. 相似文献
12.
S. Vecchio 《Journal of Thermal Analysis and Calorimetry》2007,87(1):79-83
The vaporization enthalpies of two acetanilide pesticides, alachlor
(2’,6’-diethyl-N-(methoxymethyl)-2-chloroacetanilide) and metolachlor
(2-chloro-N-(2-ethyl-6-methylphenyl)-N-[(1S)-2-methoxy-1-methylethyl] acetamide),
were determined by processing non-isothermal thermogravimetry data according
to the Clausius-Clapeyron equation. The reliability of the procedure proposed
was tested carrying out some experiments at different heating rates using
acetanilide as a reference compound. A good agreement is found among the vaporization
enthalpies derived from all the multi-heating rate experiments as well as
with the one predicted from the vapor pressure data taken from literature.
The vaporization temperatures (T
vap=470±2
K and T
vap=479±2
K) and enthalpies (Δvap
H°(436
K)=85±1 kJ mol–1 and Δvap
H°(436 K)=70±1 kJ mol–1)
for alachlor and metolachlor, were selected, respectively. 相似文献
13.
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
14.
Z. H. Zhang Z. C. Tan Y. S. Li L. X. Sun 《Journal of Thermal Analysis and Calorimetry》2006,85(3):551-557
The molar heat capacities of the room temperature
ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate (BMIBF4)
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)=
195.55+47.230 X–3.1533 X
2+4.0733 X
3+3.9126 X
4 [X=(T–125.5)/45.5] for the solid phase (80~171
K), and C
P,m (J
K–1 mol–1)=
378.62+43.929 X+16.456 X
2–4.6684 X
3–5.5876 X
4 [X=(T–285.5)/104.5] for the liquid phase (181~390
K), respectively. According to the polynomial equations and thermodynamic
relationship, the values of thermodynamic function of the BMIBF4
relative to 298.15 K were calculated in temperature range from 80 to 390 K
with an interval of 5 K. The glass translation of BMIBF4
was observed at 176.24 K. Using oxygen-bomb combustion calorimeter, the molar
enthalpy of combustion of BMIBF4 was determined to
be Δc
H
m
o=
– 5335±17 kJ mol–1. The standard
molar enthalpy of formation of BMIBF4 was evaluated
to be Δf
H
m
o=
–1221.8±4.0 kJ mol–1 at T=298.150±0.001 K. 相似文献
15.
V. A. Lukyanova T. S. Papina K. V. Didenko A. S. Alikhanyan 《Journal of Thermal Analysis and Calorimetry》2008,92(3):743-746
The standard enthalpy of combustion of crystalline silver pivalate, (CH3)3CC(O)OAg (AgPiv), was determined in an isoperibolic calorimeter with a self-sealing steel bomb, Δc
H
0 (AgPiv, cr)= −2786.9±5.6 kJ mol−1. The value of standard enthalpy of formation was derived for crystalline state: Δf
H
0(AgPiv,cr)= −466.9±5.6 kJ mol−1. Using the enthalpy of sublimation, measured earlier, the enthalpy of formation of gaseous dimer was obtained: Δf
H
0(Ag2Piv2,g)= −787±14 kJ mol−1. The enthalpy of reaction (CH3)3CC(O)OAg(cr)=Ag(cr)+(CH3)3CC(O)O.(g) was estimated, Δr
H
0=202 kJ mol−1. 相似文献
16.
O.T. Glukhova N.M. Arkhangelova A.B. Teplitsky L.F. Sukhodub I.K. Yanson Miron Kamiński 《Thermochimica Acta》1985,95(1):133-138
A low-temperature quartz resonator method for determining the enthalpy of sublimation has been described. A quartz crystal cooled to the temperature of liquid nitrogen becomes a sensitive microbalance. The method permits the value of ΔHsub to be obtained within 4–5 h and is especially useful in measuring ΔHsub values of substances with low saturated vapour pressures. The following values of ΔHsub were received for standard substances: benzoic acid, ΔHsub = (90.8±0.6) kJ mol?1 at 293–319 K: naphthalene, ΔHsub = (72.3±0.8) kJ mol?1at 293–331 K. 相似文献
17.
L. N. Zelenina Z. I. Semenova V. A. Titov T. P. Chusova 《Russian Chemical Bulletin》2004,53(8):1621-1624
The sublimation pressure of chromium trichloride was measured by the static method with a quartz membrane-gauge manometer in the temperature range of 875–1230 K. An approximating equation for the sublimation pressure vs. temperature was found. The enthalpy (259.4±4 kJ mol–1) and the entropy (224.2±3.5 J mol–1 K–1) of sublimation at 298 K were calculated. For the process 2 CrCl3(g) + Cl2(g) = 2 CrCl4(g), the following values were obtained: r
H°298 = –207.1±11.6 kJ mol–1 and r
S°298 = –173.6±10 5 J mol–1 K–1.Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1561–1564, August, 2004. 相似文献
18.
Jonathan F. Ojo Jide Ige Grace O. Ogunlusi Olanrewaju Owoyomi Esan S. Olaseni 《Transition Metal Chemistry》2006,31(6):782-785
The kinetics of the reactions between Fe(phen)
3
2+
[phen = tris–(1,10) phenanthroline] and
Co(CN)5X3− (X = Cl, Br or I) have been investigated in aqueous acidic solutions at I = 0.1 mol dm−3 (NaCl/HCl). The reactions were carried out at a fixed acid concentration ([H+] = 0.01 mol dm−3) and the second-order rate constants for the reactions at 25 °C were within the range of (0.151–1.117) dm3 mol−1 s−1. Ion-pair constants K
ip for these reactions, taking into consideration the protonation of the cobalt complexes, were 5.19 × 104, 3.00 × 102 and 4.02 × 104 mol−1 dm−3 for X = Cl, Br and I, respectively. Activation parameters measured for these systems were as follows: ΔH* (kJ K−1 mol−1) = 94.3 ± 0.6, 97.3 ± 1.0 and 109.1 ± 0.4; ΔS* (J K−1) = 69.1 ± 1.9, 74.9 ± 3.2 and 112.3 ± 1.3; ΔG* (kJ) = 73.7 ± 0.6, 75.0 ± 1.0 and 75.7 ± 0.4; E
a
(kJ) = 96.9 ± 0.3, 99.8 ± 0.4, and 122.9 ± 0.3; A (dm3 mol−1 s−1) = (7.079 ± 0.035) × 1016, (1.413 ± 0.011) × 1017, and (9.772 ± 0.027) × 1020 for X = Cl, Br, and I respectively. An outer – sphere mechanism is proposed for all the reactions. 相似文献
19.
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, δvitr
H(298 K) = (80.7 ± 3.4) kJ mol−1, and enthalpy of fusion at the temperature of fusion 1656 K, δfus
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. 相似文献
20.
《Journal of Chemical Sciences》1991,103(3):499-503
A laser flash photolysis/resonance fluorescence investigation has been carried out to study the kinetics of the overall reactions
OH + cyclopropane (1) and OH + cyclobutane (2) in the temperature range 298–490 K and at 298 K, respectively. The following
kinetic parameters have been determined: k1 =(3.9 ±0.6) 10−12exp- (2.2 ± 0.1)kcal mol−1/RT molecule−1cm3s−1, k2(298 K) = (17.5 ± 1.5)10−13molecule−1 cm3s−1. 相似文献