共查询到20条相似文献,搜索用时 31 毫秒
1.
Sargunam Caleb Noble Chandar Kannappan Santhakumar Mahadevimangalam Narayanasamy Arumugham 《Transition Metal Chemistry》2009,34(8):841-848
Twelve surfactant Schiff base ligands were synthesized from salicylaldehyde and its chloro-, bromo- and methoxy- derivatives
by condensation with long-chain aliphatic primary amines, and a number of mixed ligand cobalt(III) surfactant Schiff base
coordination complexes of the type [Co(trien)A]2+ were synthesized from the corresponding dihalogeno complexes by ligand substitution. The Schiff bases and their complexes
were characterized by physico-chemical and spectroscopic methods. The complexes form foams in aqueous solution upon shaking.
The critical micelle concentration (CMC) values of the complexes in aqueous solution were obtained from conductance measurements.
Specific conductivity data (at 303–323 K) served for the evaluation of the thermodynamics of micellization (
\Updelta G\textm0 \Updelta G_{\text{m}}^{0} ,
\Updelta H\textm0 \Updelta H_{\text{m}}^{0} ,
\Updelta S\textm0 \Updelta S_{\text{m}}^{0} ). The complexes were tested for its antimicrobial activity. 相似文献
2.
Abdel-Rahman El-Sayed Hossnia S. Mohran Hany M. Abd El-Lateef 《Monatshefte für Chemie / Chemical Monthly》2012,13(8):51-64
Abstract
The effect of adenine, adenosine, and 2,4,6-tris(2-pyridyl)-1,3,5-triazine (TPTZ) on the electrochemical and corrosion behavior of tin, indium, and tin-indium alloys in 0.5 M HClO4 solution at different temperatures was studied. The inhibition efficiency increases with an increase in the concentration of adenine and adenosine in the case of tin and indium. However, the effect of two mentioned compounds on the corrosion rate of the studied alloys gives an opposite effect. In the presence of TPTZ, the inhibition efficiency increases as the concentration of the inhibitor is increased in the case of tin. In the case of both indium and its investigated alloys, the maximum inhibition efficiency is obtained at the lowest concentration of TPTZ (10−6 M). The adsorption of the studied compounds is found to obey the Frumkin adsorption isotherm. The standard enthalpy \Updelta Hads° , \Updelta H_{\rm ads}^{^\circ } , entropy \Updelta Sads° , \Updelta S_{\rm ads}^{^\circ } , and free energy changes of adsorption \Updelta Gads° \Updelta G_{\rm ads}^{^\circ } are calculated and discussed. 相似文献3.
Manuel A. V. Ribeiro da Silva Ana Filipa L. O. M. Santos 《Journal of Thermal Analysis and Calorimetry》2010,100(2):403-411
This article reports the values of the standard (p
o = 0.1 MPa) molar enthalpies of formation, in the gaseous phase,
\Updelta\textf H\textm\texto ( \textg ), {{\Updelta}}_{\text{f}} H_{\text{m}}^{\text{o}} \left( {\text{g}} \right), at T = 298.15 K, of 2-acetyl-5-nitrothiophene and 5-nitro-2-thiophenecarboxaldehyde as −(48.8 ± 1.6) and (4.4 ± 1.3) kJ mol−1, respectively. These values were derived from experimental thermodynamic parameters, namely, the standard (p
o = 0.1 MPa) molar enthalpies of formation, in the crystalline phase,
\Updelta\textf H\textm\texto ( \textcr ) , {{\Updelta}}_{\text{f}} H_{\text{m}}^{\text{o}} \left( {\text{cr}} \right) , at T = 298.15 K, obtained from the standard molar enthalpies of combustion,
\Updelta\textc H\textm\texto , {{\Updelta}}_{\text{c}} H_{\text{m}}^{\text{o}} , measured by rotating bomb combustion calorimetry, and from the standard molar enthalpies of sublimation, at T = 298.15 K, determined from the temperature–vapour pressure dependence, obtained by the Knudsen mass loss effusion method.
The results are interpreted in terms of enthalpic increments and the enthalpic contribution of the nitro group in the substituted
thiophene ring is compared with the same contribution in other structurally similar compounds. 相似文献
4.
S. X. Xiao J. J. Zhang X. Li L. J. Ye H. W. Gu N. Ren 《Journal of Thermal Analysis and Calorimetry》2010,102(2):813-817
A ternary binuclear complex of dysprosium chloride hexahydrate with m-nitrobenzoic acid and 1,10-phenanthroline, [Dy(m-NBA)3phen]2·4H2O (m-NBA: m-nitrobenzoate; phen: 1,10-phenanthroline) was synthesized. The dissolution enthalpies of [2phen·H2O(s)], [6m-HNBA(s)], [2DyCl3·6H2O(s)], and [Dy(m-NBA)3phen]2·4H2O(s) in the calorimetric solvent (VDMSO:VMeOH = 3:2) were determined by the solution–reaction isoperibol calorimeter at 298.15 K to be
\Updelta\texts H\textmq \Updelta_{\text{s}} H_{\text{m}}^{\theta } [2phen·H2O(s), 298.15 K] = 21.7367 ± 0.3150 kJ·mol−1,
\Updelta\texts H\textmq \Updelta_{\text{s}} H_{\text{m}}^{\theta } [6m-HNBA(s), 298.15 K] = 15.3635 ± 0.2235 kJ·mol−1,
\Updelta\texts H\textmq \Updelta_{\text{s}} H_{\text{m}}^{\theta } [2DyCl3·6H2O(s), 298.15 K] = −203.5331 ± 0.2200 kJ·mol−1, and
\Updelta\texts H\textmq \Updelta_{\text{s}} H_{\text{m}}^{\theta } [[Dy(m-NBA)3phen]2·4H2O(s), 298.15 K] = 53.5965 ± 0.2367 kJ·mol−1, respectively. The enthalpy change of the reaction was determined to be
\Updelta\textr H\textmq = 3 6 9. 4 9 ±0. 5 6 \textkJ·\textmol - 1 . \Updelta_{\text{r}} H_{\text{m}}^{\theta } = 3 6 9. 4 9 \pm 0. 5 6 \;{\text{kJ}}\cdot {\text{mol}}^{ - 1} . According to the above results and the relevant data in the literature, through Hess’ law, the standard molar enthalpy of
formation of [Dy(m-NBA)3phen]2·4H2O(s) was estimated to be
\Updelta\textf H\textmq \Updelta_{\text{f}} H_{\text{m}}^{\theta } [[Dy(m-NBA)3phen]2·4H2O(s), 298.15 K] = −5525 ± 6 kJ·mol−1. 相似文献
5.
Metallosurfactant complexes of the type trans- [Co(DH)2(HA)X], where DH = Dimethyl glyoxime, HA = Hexadecyl amine and X = Cl−, Br−, I−, N3
−, NO2
− or SCN−, were synthesized and characterized by physico-chemical and spectroscopic methods. In addition, the single crystal X-ray
structure of the ionic complex trans-[Co(DH)2(HA)2][Co(DH)2(I)2)] is presented. The critical micelle concentration values of the complexes in ethanol were obtained by measuring the absorption
at 290 nm. Specific conductivity data (at 303–313 K) served for the evaluation of the thermodynamics of micellization
) \left( {\Updelta G^{0}_{{{\text{m}}}}, \Updelta H^{0}_{{{\text{m}}}}, \Updelta S^{0}_{\text{m}} } \right) . Steady-state photolysis, cyclic voltammetry and biological activities of the complexes were studied. The compounds were
tested for antimicrobial activity. 相似文献
6.
Simona Peterlin Odon Planinšek Isabel Moutinho Paulo Ferreira Darko Dolenc 《Cellulose (London, England)》2010,17(6):1095-1102
Unbleached TMP spruce fibers were stepwise delignified by KMnO4/H2SO4 and five partly delignified samples were obtained. Fibers were characterized in terms of carboxylic groups, lignin and hemicelluloses
content. IGC measurements were performed in the untreated fibers and in the five delignified fiber samples, as well as in
microcrystalline cellulose (MCC). Different parameters, such as the dispersive component of the surface free energy (gs d \gamma_{{_{s} }}^{d} ), the free energy and the enthalpy of adsorption with nonpolar probes (
\Updelta Gad \Updelta G_{a}^{d} and
\Updelta Had \Updelta H_{a}^{d} , respectively), as well as the specific interactions with polar probes, quantified by the free energy and the enthalpy of
adsorption (
\Updelta Gas \Updelta G_{a}^{s} and
\Updelta Has \Updelta H_{a}^{s} , respectively), were determined. The values of gs d \gamma_{{_{s} }}^{d} and
\Updelta Gad \Updelta G_{a}^{d} are for all samples lower than for pure cellulose and vary slightly with the amount of lignin. For small contents of lignin,
the values of
\Updelta Gas \Updelta G_{a}^{s} of the acidic probes decrease with the delignification whereas those of the basic probes increase, pointing to a rather acidic
character of the fibers due to the increase of the relative amount of the carbohydrates. The values for MCC corroborate these
findings. Despite the substantial variation in the carboxylic group content during delignification, no clear tendencies were
detected regarding the affinity with the basic probes. 相似文献
7.
K. Tebbji H. Oudda B. Hammouti M. Benkaddour S. S. Al-Deyab A. Aouniti S. Radi A. Ramdani 《Research on Chemical Intermediates》2011,37(8):985-1007
The effect of some prepared compounds, namely 3,5-dimethyl-1H-pyrazole (P1), 3(5)-amino-5(3)-methylpyrazole (P2), and 1′,3,5,5′-tetramethyl-1′H-1,3′-bipyrazole (P3), on the corrosion behaviour of steel in 1.0 M hydrochloric acid solution as corrosive medium has been investigated at 308 K using weight-loss measurement, potentiodynamic
polarisation, linear polarisation, and impedance spectroscopy (EIS). Generally, inhibition efficiency of the investigated
compounds was found to depend on the concentration and nature of the inhibitor. P3 was a better inhibitor than P1 and P2,
and its inhibition efficiency increased with increasing concentration of inhibitor, attaining 94% above 10−3
M. Potentiodynamic polarisation studies clearly reveal that P3 acts essentially as a cathodic inhibitor. E (%) values obtained from different methods are in reasonably good agreement. EIS measurements show an increase of transfer
resistance with inhibitor concentration. Partial π-charge on atoms was calculated. Correlation between the highest occupied
molecular orbital energy E
HOMO and inhibition efficiencies was sought. The temperature effect on the corrosion behaviour of steel in 1.0 M HCl without and with different concentrations of inhibitor P3 was studied in the temperature range 308 to 343 K. Thermodynamic
data, for example heat of adsorption (
\Updelta H\textads° \Updelta H_{\text{ads}}^{^\circ } ), entropy of adsorption (
\Updelta S\textads° \Updelta S_{\text{ads}}^{^\circ } ) and free energy of adsorption (
\Updelta G\textads° \Updelta G_{\text{ads}}^{^\circ } ) were calculated by use of thermodynamic equations. Kinetic activation data, for example E
a, ΔH*, ΔS* and pre-exponential factor, were calculated, and are discussed. The inhibiting action of P3 on the corrosion of steel in
1–10 M hydrochloric acid was also studied by weight-loss measurement. The rate constant and reaction constant were calculated for
the corrosion reactions. Adsorption of P3 on the steel surface in 1.0 M HCl follows the Langmuir isotherm model. 相似文献
8.
Lubka Atanasova Ginka Baikusheva-Dimitrova 《Journal of Thermal Analysis and Calorimetry》2012,107(2):809-812
The experimental results obtained for the specific molar heat capacity of the tellurites Yb2(TeO3)3, Dy2(TeO3)3 and Er2(TeO3)3 are processed by the least squares method. The temperature dependence of the specific molar heat capacity derived is used
to determine the thermodynamic properties: entropy
( \UpdeltaT¢T Sm0 ), \left( {\Updelta_{T\prime }^{T} S_{m}^{0} } \right), enthalpy
( \UpdeltaT¢T Hm0 ) \left( {\Updelta_{T\prime }^{T} H_{m}^{0} } \right) and Gibbs function
( \UpdeltaT¢T Gm0 ) \left( {\Updelta_{T\prime }^{T} G_{m}^{0} } \right) of the tellurites Yb2(TeO3)3, Dy2(TeO3)3 and Er2(TeO3)3. 相似文献
9.
Ricardo Picciochi Hermínio P. Diogo Manuel E. Minas da Piedade 《Journal of Thermal Analysis and Calorimetry》2010,100(2):391-401
Combustion calorimetry, Calvet-drop sublimation calorimetry, and the Knudsen effusion method were used to determine the standard
(p
o = 0.1 MPa) molar enthalpies of formation of monoclinic (form I) and gaseous paracetamol, at T = 298.15 K:
\Updelta\textf H\textm\texto ( \textC 8 \textH 9 \textO 2 \textN,\text cr I ) = - ( 4 10.4 ±1. 3)\text kJ \textmol - 1 \Updelta_{\text{f}} H_{\text{m}}^{\text{o}} \left( {{\text{C}}_{ 8} {\text{H}}_{ 9} {\text{O}}_{ 2} {\text{N}},{\text{ cr I}}} \right) = - ( 4 10.4 \pm 1. 3){\text{ kJ}}\;{\text{mol}}^{ - 1} and
\Updelta\textf H\textm\texto ( \textC 8 \textH 9 \textO 2 \textN,\text g ) = - ( 2 80.5 ±1. 9)\text kJ \textmol - 1 . \Updelta_{\text{f}} H_{\text{m}}^{\text{o}} \left( {{\text{C}}_{ 8} {\text{H}}_{ 9} {\text{O}}_{ 2} {\text{N}},{\text{ g}}} \right) = - ( 2 80.5 \pm 1. 9){\text{ kJ}}\;{\text{mol}}^{ - 1} . From the obtained
\Updelta\textf H\textm\texto ( \textC 8 \textH 9 \textO 2 \textN,\text cr I ) \Updelta_{\text{f}} H_{\text{m}}^{\text{o}} \left( {{\text{C}}_{ 8} {\text{H}}_{ 9} {\text{O}}_{ 2} {\text{N}},{\text{ cr I}}} \right) value and published data, it was also possible to derive the standard molar enthalpies of formation of the two other known
polymorphs of paracetamol (forms II and III), at 298.15 K:
\Updelta\textf H\textm\texto ( \textC 8 \textH 9 \textO 2 \textN,\text crII ) = - ( 40 8.4 ±1. 3)\text kJ \textmol - 1 \Updelta_{\text{f}} H_{\text{m}}^{\text{o}} \left( {{\text{C}}_{ 8} {\text{H}}_{ 9} {\text{O}}_{ 2} {\text{N}},{\text{ crII}}} \right) = - ( 40 8.4 \pm 1. 3){\text{ kJ}}\;{\text{mol}}^{ - 1} and
\Updelta\textf H\textm\texto ( \textC 8 \textH 9 \textO 2 \textN,\text crIII ) = - ( 40 7.4 ±1. 3)\text kJ \textmol - 1 . \Updelta_{\text{f}} H_{\text{m}}^{\text{o}} \left( {{\text{C}}_{ 8} {\text{H}}_{ 9} {\text{O}}_{ 2} {\text{N}},{\text{ crIII}}} \right) = - ( 40 7.4 \pm 1. 3){\text{ kJ}}\;{\text{mol}}^{ - 1} . The proposed
\Updelta\textf H\textm\texto ( \textC 8 \textH 9 \textO 2 \textN,\text g ) \Updelta_{\text{f}} H_{\text{m}}^{\text{o}} \left( {{\text{C}}_{ 8} {\text{H}}_{ 9} {\text{O}}_{ 2} {\text{N}},{\text{ g}}} \right) value, together with the experimental enthalpies of formation of acetophenone and 4′-hydroxyacetophenone, taken from the
literature, and a re-evaluated enthalpy of formation of acetanilide,
\Updelta\textf H\textm\texto ( \textC 8 \textH 9 \textON,\text g ) = - ( 10 9. 2 ± 2. 2)\text kJ \textmol - 1 , \Updelta_{\text{f}} H_{\text{m}}^{\text{o}} \left( {{\text{C}}_{ 8} {\text{H}}_{ 9} {\text{ON}},{\text{ g}}} \right) = - ( 10 9. 2\,\pm\,2. 2){\text{ kJ}}\;{\text{mol}}^{ - 1} , were used to assess the predictions of the B3LYP/cc-pVTZ and CBS-QB3 methods for the enthalpy of a isodesmic and isogyric
reaction involving those species. This test supported the reliability of the theoretical methods, and indicated a good thermodynamic
consistency between the
\Updelta\textf H\textm\texto \Updelta_{\text{f}} H_{\text{m}}^{\text{o}} (C8H9O2N, g) value obtained in this study and the remaining experimental data used in the
\Updelta\textr H\textm\texto \Updelta_{\text{r}} H_{\text{m}}^{\text{o}} calculation. It also led to the conclusion that the presently recommended enthalpy of formation of gaseous acetanilide in
Cox and Pilcher and Pedley’s compilations should be corrected by ~20 kJ mol−1. 相似文献
10.
The molar enthalpies of solution of 2-aminopyridine at various molalities were measured at T=298.15 K in double-distilled water by means of an isoperibol solution-reaction calorimeter. According to Pitzer’s theory,
the molar enthalpy of solution of the title compound at infinite dilution was calculated to be DsolHm¥ = 14.34 kJ·mol-1\Delta_{\mathrm{sol}}H_{\mathrm{m}}^{\infty} = 14.34~\mbox{kJ}\cdot\mbox{mol}^{-1}, and Pitzer’s ion interaction parameters bMX(0)L, bMX(1)L\beta_{\mathrm{MX}}^{(0)L}, \beta_{\mathrm{MX}}^{(1)L}, and CMXfLC_{\mathrm{MX}}^{\phi L} were obtained. Values of the relative apparent molar enthalpies (
φ
L) and relative partial molar enthalpies of the compound ([`(L)]2)\bar{L}_{2}) were derived from the experimental enthalpies of solution of the compound. The standard molar enthalpy of formation of the
cation C5H7N2 +\mathrm{C}_{5}\mathrm{H}_{7}\mathrm{N}_{2}^{ +} in aqueous solution was calculated to be DfHmo(C5H7N2+,aq)=-(2.096±0.801) kJ·mol-1\Delta_{\mathrm{f}}H_{\mathrm{m}}^{\mathrm{o}}(\mathrm{C}_{5}\mathrm{H}_{7}\mathrm{N}_{2}^{+},\mbox{aq})=-(2.096\pm 0.801)~\mbox{kJ}\cdot\mbox{mol}^{-1}. 相似文献
11.
Donald A. Palmer Pascale Bénézeth Caibin Xiao David J. Wesolowski Lawrence M. Anovitz 《Journal of solution chemistry》2011,40(4):680-702
Results of solubility experiments involving crystalline nickel oxide (bunsenite) in aqueous solutions are reported as functions
of temperature (0 to 350 °C) and pH at pressures slightly exceeding (with one exception) saturation vapor pressure. These
experiments were carried out in either flow-through reactors or a hydrogen-electrode concentration cell for mildly acidic
to near neutral pH solutions. The results were treated successfully with a thermodynamic model incorporating only the unhydrolyzed
aqueous nickel species (viz., Ni2+) and the neutrally charged hydrolyzed species (viz., Ni(OH)20)\mathrm{Ni(OH)}_{2}^{0}). The thermodynamic quantities obtained at 25 °C and infinite dilution are, with 2σ uncertainties:
log10Ks0o = (12.40 ±0.29),\varDeltarGmo = -(70. 8 ±1.7)\log_{10}K_{\mathrm{s0}}^{\mathrm{o}} = (12.40 \pm 0.29),\varDelta_{\mathrm{r}}G_{m}^{\mathrm{o}} = -(70. 8 \pm 1.7) kJ⋅mol−1;
\varDeltarHmo = -(105.6 ±1.3)\varDelta_{\mathrm{r}}H_{m}^{\mathrm{o}} = -(105.6 \pm 1.3) kJ⋅mol−1;
\varDeltarSmo = -(116.6 ±3.2)\varDelta_{\mathrm{r}}S_{m}^{\mathrm{o}} =-(116.6 \pm 3.2) J⋅K−1⋅mol−1;
\varDeltarCp,mo = (0 ±13)\varDelta_{\mathrm{r}}C_{p,m}^{\mathrm{o}} = (0 \pm 13) J⋅K−1⋅mol−1; and log10Ks2o = -(8.76 ±0.15)\log_{10}K_{\mathrm{s2}}^{\mathrm{o}} = -(8.76 \pm 0.15);
\varDeltarGmo = (50.0 ±1.7)\varDelta_{\mathrm{r}}G_{m}^{\mathrm{o}} = (50.0 \pm 1.7) kJ⋅mol−1;
\varDeltarHmo = (17.7 ±1.7)\varDelta_{\mathrm{r}}H_{m}^{\mathrm{o}} = (17.7 \pm 1.7) kJ⋅mol−1;
\varDeltarSmo = -(108±7)\varDelta_{\mathrm{r}}S_{m}^{\mathrm{o}} = -(108\pm 7) J⋅K−1⋅mol−1;
\varDeltarCp,mo = -(108 ±3)\varDelta_{\mathrm{r}}C_{p,m}^{\mathrm{o}} = -(108 \pm 3) J⋅K−1⋅mol−1. These results are internally consistent, but the latter set differs from those gleaned from previous studies recorded in
the literature. The corresponding thermodynamic quantities for the formation of Ni2+ and Ni(OH)20\mathrm{Ni(OH)}_{2}^{0} are also estimated. Moreover, the Ni(OH)3 -\mathrm{Ni(OH)}_{3}^{ -} anion was never observed, even in relatively strong basic solutions (mOH - = 0.1m_{\mathrm{OH}^{ -}} = 0.1 mol⋅kg−1), contrary to the conclusions drawn from all but one previous study. 相似文献
12.
S. Chauhan M. S. Chauhan Deepika Kaushal V. K. Syal J. Jyoti 《Journal of solution chemistry》2010,39(5):622-638
Sound velocity and density measurements of aqueous solutions of the anionic surfactant SDS (sodium dodecyl sulfate) and the
cationic surfactant CTAB (cetyltrimethylammonium bromide) with the drug furosemide (0.002 and 0.02 mol⋅dm−3) have been carried out in the temperature range 20–40 °C. From these measurements, the compressibility coefficient (β), apparent molar volume (φ
v
) and apparent molar compressibility (φ
κ
) have been computed. From electrical conductivity measurements, the critical micelle concentrations (CMCs) of SDS and CTAB
has been determined in the above aqueous furosemide solutions. From the CMC values as a function of temperature, various thermodynamic
parameters have been evaluated: the standard enthalpy change (DHmo\Delta H_{\mathrm{m}}^{\mathrm{o}}), standard entropy change (DSmo\Delta S_{\mathrm{m}}^{\mathrm{o}}), and standard Gibbs energy change (DGmo\Delta G_{\mathrm{m}}^{\mathrm{o}}) for micellization. This work also included viscosity studies of aqueous solutions of SDS and CTAB with the drug in order
to determine the relative viscosity (η
r). UV-Vis studies have also been carried for the ternary drug/surfactant/water system having SDS in the concentration range
0.002–0.014 mol⋅dm−3. All of these parameters are discussed in terms of drug–drug, drug–solvent and drug–surfactant interactions resulting from
of various electrostatic and hydrophobic interactions. 相似文献
13.
Ye Qin Wei-Feng Xue Jian-Guo Liu Wei-Guo Xu Chuan-Wei Yan Jia-Zhen Yang 《Journal of solution chemistry》2010,39(6):857-863
The molar enthalpies of solution of VOSO4⋅3.52H2O(s) at various molalities in water and in aqueous sulfuric acid (0.1 mol⋅kg−1), Δsol
H
m, were measured by a solution-reaction isoperibol calorimeter at 298.15±0.01 K. An improved Archer’s method to estimate the
standard molar enthalpy of solution, DsolH0m\Delta_{\mathrm{sol}}H^{0}_{\mathrm{m}}, was put forward. In terms of the improved method, the values of DsolH0m=-24.12±0.03 kJ·mol-1\Delta_{\mathrm{sol}}H^{0}_{\mathrm{m}}=-24.12\pm 0.03~\mbox{kJ}{\cdot}\mbox{mol}^{-1} of VOSO4⋅3.52H2O(s) in water and DsolH0m=-15.38±0.06 kJ·mol-1\Delta_{\mathrm{sol}}H^{0}_{\mathrm{m}}=-15.38\pm 0.06~\mbox{kJ}{\cdot}\mbox{mol}^{-1} in aqueous sulfuric acid were obtained, respectively. The data indicates that the energy state of VOSO4 in aqueous H2SO4 is higher than that in pure water. 相似文献
14.
Ju-Lan Zeng Sai-Bo Yu Bo Tong Li-Xian Sun Zhi-Cheng Tan Zhong Cao Dao-Wu Yang Jing-Nan Zhang 《Journal of Thermal Analysis and Calorimetry》2011,103(3):1087-1093
An N-tert-butyloxycarbonylated organic synthesis intermediate, (S)-tert-butyl 1-phenylethylcarbamate, was prepared and investigated by means of differential scanning calorimetry (DSC) and thermogravimetry
(TG). The molar heat capacities of (S)-tert-butyl 1-phenylethylcarbamate were precisely determined by means of adiabatic calorimetry over the temperature range of 80-380 K.
There was a solid–liquid phase transition exhibited during the heating process with the melting point of 359.53 K. The molar
enthalpy and entropy of this transition were determined to be 29.73 kJ mol−1 and 82.68 J K−1 mol−1 based on the experimental C
p–T curve, respectively. The thermodynamic functions, [HT0 - H298.150 H_{T}^{0} - H_{298.15}^{0} ] and [ST0 - S298.150 S_{T}^{0} - S_{298.15}^{0} ], were calculated from the heat capacity data in the temperature range of 80–380 K with an interval of 5 K. TG experiment
showed that the pyrolysis of the compound was started at the temperature of 385 K and terminated at 510 K within one step. 相似文献
15.
Jian-Hua Yi Feng-Qi Zhao Ying-Hui Ren Bo-Zhou Wang Cheng Zhou Xiao-Ning Ren Si-Yu Xu Hai-Xia Hao Rong-Zu Hu 《Journal of Thermal Analysis and Calorimetry》2011,104(3):1029-1036
The high-pressure thermal properties and their correlation with burning rates of the composite modified double base (CMDB)
propellants containing 3,6-bis (1H-1,2,3,4-tetrazol-5-yl-amino)-1,2,4,5-tetrazine (BTATz), a substitute of hexogen (RDX),
were investigated using the high-pressure differential scanning calorimetry (PDSC). The results show that there is a main
exothermal decomposition process with the heating of each propellant. High pressure can restrain the volatilization of NG,
accelerate the main decomposition reaction, and make the reaction occur easily. High pressure can change the main decomposition
reaction mechanism function and kinetics, and the control process obeys the rule of Avrami–Erofeev equation at high pressure
and chemical reaction at normal pressure. However, the mechanism function can not be changed by the ballistic modifier. The
correlation between PDSC characteristic values and burning rates was carried out and found that u and
( p \Updelta H\textd / \Updelta T ) 1 / 2 \left( {p \, \Updelta H_{\text{d}} { / }\Updelta T} \right)^{ 1 / 2} keep a good linear relation, k
u
keeps a similar changing trend with u, and it can be used to study the effect of the ballistic modifier or the other component on the burning rates. 相似文献
16.
Thato N. Mtshali Walter Purcell Hendrik G. Visser Steven S. Basson 《Transition Metal Chemistry》2008,33(4):481-491
The kinetics of the reaction between [ReN(H2O)-(CN)4]2− with different κ2
N,O-donor ligands (quin− and 2,3-dipic−, respectively) have been studied in the pH 4–12 range in aqueous solution. Two consecutive reaction steps with the formation
of the [ReN(η1-quin)(CN)4]3− and [ReN(μ2-quin) (CN)3]2− complexes, respectively, were spectrophotometrically observed and kinetically investigated. The same reaction mechanism is
proposed for these two ligands. The first fast reaction (for quin−) is attributed to the aqua substitution of [ReN(H2O)(CN)4]2− with forward and reverse rate constants of 1.96(5) × 10−1 M−1 s−1 and 5.6(3) × 10−2 s−1, while a rate of 2.64(3) M−1 s−1 was observed for the reaction between the conjugate base [ReN(OH)(CN)4]3− and quin− at 40.2 °C. Due to small absorbance changes, it was difficult to obtain any good quality data for the fast reactions for
2,3-dipic−. The second, slower reaction is attributed to cyano substitution with rate constants (k
3
K
1) of 4.17(4) × 10−3 for quin− and 4.68(7) × 10−3 M−1 s−1 for 2,3-dipic−, at 80.02 °C, respectively. The acid dissociation constant for the aqua complex was spectrophotometrically determined as
11.58(3) and 11.54(2) and kinetically as 11.51(8) and 11.41(1), at 80.4 °C, respectively. Negative values of −83.5(2) and −144.1(2) J K−1 mol−1 as well as the of 71.4(3) and 47.3(3) kJ mol−1, for the slow quin− and 2,3-dipic− reactions, respectively, point to an ordered transition state where bond formation is responsible for the major driving force
of the reaction. The and for the fast forward reaction of quin− is indicative of expected associative activation in the transition state.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
17.
The electrical conductances of pyridinium dichromate have been measured in N,N-dimethyl formamide–water mixtures of different
compositions in the temperature range 283–313 K. The limiting molar conductance, Λ0, association constant of the ion pair, K
A, and dissociation constant K
C have been calculated using the Shedlovsky and Kraus–Bray equations. The effective ionic radii (r
i
) of C5H5NH+ and Cr2O7 -\mathrm{Cr}_{2}\mathrm{O}_{7}^{ -} have been determined from the Li0\Lambda_{i}^{0} values using Gill’s modification of Stokes’ law. The influence of the mixed solvent composition on the solvation of ions
is discussed with the help of the ‘R’-factor (
R = \frachL ±0(solvent)hL ±0(water)R = \frac{\eta \Lambda_{ \pm}^{0}(\mathrm{solvent})}{\eta\Lambda_{ \pm}^{0}(\mathrm{water})}). Thermodynamic parameters are evaluated and reported. The results of this study are interpreted in terms of ion–solvent
interactions and solvent properties. 相似文献
18.
Shu-Jian Chen Julia K. C. Abbott Carlos A. Steren Zi-Ling Xue 《Journal of Cluster Science》2010,21(3):325-337
Metal cage complexes [(Me2N)3MO]4 (M = Nb, 3; Ta, 4) have been prepared from the reactions of M(NMe2)5 (M = Nb, 1; Ta, 2) with water. Single crystal X-ray diffraction studies of 3 and 4 reveal that they adopt cubane-like structures with M–O bridges. Variable-temperature NMR studies of –NMeAMeB rotations in 3 and 4 have been performed to give the following activation parameters for the exchanges: ΔH
≠ = −1.4(1.1) kJ/mol, ΔS
≠ = −209(8) J/mol K,
\Updelta G 30 8 \textK 1 = 6 4( 2) \textkJ/\textmol \Updelta G_{{_{{ 30 8\;{\text{K}}}} }}^{{^{ \ne } }} = 6 4\left( 2\right)\;{\text{kJ}}/{\text{mol}} for 3, and ΔH
≠ = −0.9(1.2) kJ/mol, ΔS
≠ = −2.1(0.2) × 102 J/mol K,
\Updelta G 30 8 \textK 1 = 6 3( 6) \textkJ/\textmol \Updelta G_{{ 30 8\;{\text{K}}}}^{{^{ \ne } }} = 6 3\left( 6\right)\;{\text{kJ}}/{\text{mol}} for 4. 相似文献
19.
The apparent molar volumes V
2,φ
, apparent molar isentropic compressibilities K
S,2,φ
, and enthalpies of dilution of aqueous glycine, alanine, α-amino butyric acid, valine, and leucine have been determined in aqueous 1.0 and 2.0 mol⋅dm−3 sorbitol solutions at 298.15 K. These data have been used to calculate the infinite dilution standard partial molar volumes
V2,m0V_{2,m}^{0}, partial molar isentropic compressibilities KS,2,m0K_{S,2,m}^{0}, and enthalpies of dilution Δdil
H
0 of the amino acids in aqueous sorbitol, along with the standard partial molar quantities of transfer of the amino acids from
water to aqueous sorbitol. The linear correlation of V2,m0V_{2,m}^{0} for this homologous series of amino acids has been utilized to calculate the contribution to V20V_{2}^{0} of the charged end groups (NH3+\mathrm{NH}_{3}^{+}, COO−), the CH2 group, and other alkyl chains of the amino acids. The results for the standard partial molar volumes of transfer, compressibilites
and enthalpies of dilution from water to aqueous sorbitol solutions have been correlated and interpreted in terms of ion–polar,
ion–hydrophobic, and hydrophobic–hydrophobic group interactions. A comparison of these thermodynamic properties of transfer
suggest that an enhancement of the hydrophilic/polar group interactions is operating in ternary systems of amino acid, sorbitol,
and water. 相似文献
20.
Manuel A. V. Ribeiro da Silva Ana I. M. C. Lobo Ferreira 《Journal of Thermal Analysis and Calorimetry》2010,100(2):447-455
The standard (p° = 0.1 MPa) molar enthalpies of formation in the crystalline state of the 2-, 3- and 4-hydroxymethylphenols, $ {{\Updelta}}_{\text{f}} H_{\text{m}}^{\text{o}} ( {\text{cr)}} = \, - ( 3 7 7. 7 \pm 1. 4)\,{\text{kJ}}\,{\text{mol}}^{ - 1} $ , $ {{\Updelta}}_{\text{f}} H_{\text{m}}^{\text{o}} ( {\text{cr) }} = - (383.0 \pm 1.4) \, \,{\text{kJ}}\,{\text{mol}}^{ - 1} $ and $ {{\Updelta}}_{\text{f}} H_{\text{m}}^{\text{o}} ( {\text{cr)}} = - (382.7 \pm 1.4)\,{\text{kJ}}\,{\text{mol}}^{ - 1} $ , respectively, were derived from the standard molar energies of combustion, in oxygen, to yield CO2(g) and H2O(l), at T = 298.15 K, measured by static bomb combustion calorimetry. The Knudsen mass-loss effusion technique was used to measure the dependence of the vapour pressure of the solid isomers of hydroxymethylphenol with the temperature, from which the standard molar enthalpies of sublimation were derived using the Clausius–Clapeyron equation. The results were as follows: $ \Updelta_{\rm cr}^{\rm g} H_{\rm m}^{\rm o} = (99.5 \pm 1.5)\,{\text{kJ}}\,{\text{mol}}^{ - 1} $ , $ \Updelta_{\rm cr}^{\rm g} H_{\rm m}^{\rm o} = (116.0 \pm 3.7) \,{\text{kJ}}\,{\text{mol}}^{ - 1} $ and $ \Updelta_{\rm cr}^{\rm g} H_{\rm m}^{\rm o} = (129.3 \pm 4.7)\,{\text{ kJ mol}}^{ - 1} $ , for 2-, 3- and 4-hydroxymethylphenol, respectively. From these values, the standard molar enthalpies of formation of the title compounds in their gaseous phases, at T = 298.15 K, were derived and interpreted in terms of molecular structure. Moreover, using estimated values for the heat capacity differences between the gas and the crystal phases, the standard (p° = 0.1 MPa) molar enthalpies, entropies and Gibbs energies of sublimation, at T = 298.15 K, were derived for the three hydroxymethylphenols. 相似文献