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1.
《The Journal of chemical thermodynamics》2007,39(11):1413-1417
A visible spectrophotometric method has been developed for the reaction kinetics of o-phenylenediamine in the presence of gold (III). The method is based on the measurement of the absorbance of the reaction o-phenylenediamine and gold (III). Optimum conditions for the reaction were established as pH 6 at λ = 466 nm.When the reaction kinetic of o-phenylenediamine by gold (III) was investigated, it was observed that the following rate formula was found as ln (A/A0) = −kt, according to absorbance measurements. The activation energy Ea and Arrhenius constant A were calculated from the Arrhenius equation as 1.009 kJ · mol−1 and 3.46 · 10−2 s−1, respectively. Other activation thermodynamic parameters, entropy, ΔS (J · mol−1 · K−1), enthalpy, ΔH (kJ · mol−1), Gibbs free energy, ΔG (kJ · mol−1) and equilibrium constant, Ke were calculated at T = (283.2, 303.2, 323.2, and 343.2) K. The study was exothermic due to the decrease of entropy and was a non-spontaneous process during activation. 相似文献
2.
《The Journal of chemical thermodynamics》2006,38(2):152-157
Vapour pressures of water over saturated solutions of cesium chloride, cesium bromide, cesium nitrate, cesium sulfate, cesium formate, and cesium oxalate were determined as a function of temperature. These vapour pressures were used to evaluate the water activities, osmotic coefficients and molar enthalpies of vapourization. Molar enthalpies of solution of cesium chloride, ΔsolHm(T = 295.73 K; m = 0.0622 mol · kg−1) = (17.83 ± 0.50) kJ · mol−1; cesium bromide, ΔsolHm(T = 293.99 K; m = 0.0238 mol · kg−1) = (26.91 ± 0.59) kJ · mol−1; cesium nitrate, ΔsolHm(T = 294.68 K; m = 0.0258 mol · kg−1) = (37.1 ± 2.3) kJ · mol−1; cesium sulfate, ΔsolHm(T = 296.43 K; m = 0.0284 mol · kg−1) = (16.94 ± 0.43) kJ · mol−1; cesium formate, ΔsolHm(T = 295.64 K; m = 0.0283 mol · kg−1) = (11.10 ± 0.26) kJ · mol−1 and ΔsolHm(T = 292.64 K; m = 0.0577 mol · kg−1) = (11.56 ± 0.56) kJ · mol−1; and cesium oxalate, ΔsolHm(T = 291.34 K; m = 0.0143 mol · kg−1) = (22.07 ± 0.16) kJ · mol−1 were determined calorimetrically. The purity of the chemicals was generally greater than 0.99 mass fraction, except for HCOOCs and (COOCs)2 where purities were approximately 0.95 and 0.97 mass fraction, respectively. The uncertainties are one standard deviations. 相似文献
3.
《The Journal of chemical thermodynamics》2004,36(2):79-86
Low-temperature heat capacities of the 9-fluorenemethanol (C14H12O) have been precisely measured with a small sample automatic adiabatic calorimeter over the temperature range between T=78 K and T=390 K. The solid–liquid phase transition of the compound has been observed to be Tfus=(376.567±0.012) K from the heat-capacity measurements. The molar enthalpy and entropy of the melting of the substance were determined to be ΔfusHm=(26.273±0.013) kJ · mol−1 and ΔfusSm=(69.770±0.035) J · K−1 · mol−1. The experimental values of molar heat capacities in solid and liquid regions have been fitted to two polynomial equations by the least squares method. The constant-volume energy and standard molar enthalpy of combustion of the compound have been determined, ΔcU(C14H12O, s)=−(7125.56 ± 4.62) kJ · mol−1 and ΔcHm∘(C14H12O, s)=−(7131.76 ± 4.62) kJ · mol−1, by means of a homemade precision oxygen-bomb combustion calorimeter at T=(298.15±0.001) K. The standard molar enthalpy of formation of the compound has been derived, ΔfHm∘(C14H12O,s)=−(92.36 ± 0.97) kJ · mol−1, from the standard molar enthalpy of combustion of the compound in combination with other auxiliary thermodynamic quantities through a Hess thermochemical cycle. 相似文献
4.
《Polyhedron》1999,18(6):811-815
Oxidative addition of H–R (H--Ph and H2) to trans-Ir(--Ph)(CO)(PPh3)2 (2) gives the initial products, cis, cis-Ir(H)(--Ph)2(CO)(PPh3)2 (3a) and cis, cis-Ir(H)2(--Ph)(CO)(PPh3)2 (3b), respectively. Both cis-bis(PPh3) complexes, 3a and 3b undergo isomerization to give the trans-bis(PPh3) complexes, trans, trans-Ir(H)(--Ph)2(CO)(PPh3)2 (4a) and cis, trans-Ir(H)2(--Ph)(CO)(PPh3)2 (4b). The isomerization, 3b→4b is first order with respect to 3b with k1=6.37×10−4 s−1 at 25°C under N2 in CDCl3. The reaction rate (k1) seems independent of the concentration of H2. A large negative entropy of activation (ΔS≠=−24.9±5.7 cal deg−1 mol−1) and a relatively small enthalpy of activation (ΔH≠=14.5±3.3 kcal mol−1) were obtained in the temperature range 15∼35°C for the isomerization, 3b→4b under 1 atm of H2. 相似文献
5.
《Journal of organometallic chemistry》2007,692(1-3):395-401
The complex cis-Pt(Ph3Ge)2(PMe2Ph)2 underwent smooth isomerization to give the trans-isomer at room temperature via an associative five-coordinated intermediate. Thermodynamic parameters and activation energy for the cis to trans isomerization were obtained, ΔH# = 105 kJ mol−1, ΔS# = 12.5 J mol−1 K−1, and Ea = 107 kJ mol−1, respectively. Heating of trans-Pt(Ph3Ge)2(PMe2Ph)2 at 50 °C for 36 days produced trans-PtPh(Ph3Ge)(PMe2Ph)2 followed by the formation of trans-PtPh2(PMe2Ph)2, Pt(PMe2Ph)4, and Ph4Ge finally via elimination of the phenyl group from Ph3Ge ligand with liberation of the Ph2Ge unit and subsequent reductive elimination of the remaining Ph3Ge ligand at 80 °C for 1 month. 相似文献
6.
《Tetrahedron: Asymmetry》2014,25(22):1456-1465
A method using (S)-(+)-2-methoxy-2-(1-naphthyl)propionic acid 1 (MαNP acid) has been applied to acetylene alcohols 4–14 to determine their absolute configurations by 1H NMR anisotropy and/or X-ray crystallography. Diastereomeric MαNP esters prepared from racemic acetylene alcohols and (S)-(+)-MαNP acid 1 were easily separable by HPLC on silica gel. From the 1H NMR anisotropy Δδ data of separated diastereomeric MαNP esters {Δδ = δ (R,X) − δ(S,X) = δ(2nd fr.) − δ(1st fr.)}, the absolute configurations of the first eluted esters were determined. This MαNP acid method has been successfully applied to various acetylene alcohols 4–12 and 14. In the case of MαNP esters 21b, 24a, and 26a, their absolute configurations were unambiguously determined by X-ray crystallography, which confirmed the absolute configuration assignments performed by 1H NMR anisotropy. These acetylene alcohol MαNP esters can serve as key intermediates for the synthesis of enantiopure aliphatic chain alcohols with established absolute configurations as described in Part 2 of this series. 相似文献
7.
《The Journal of chemical thermodynamics》2002,34(11):1777-1785
The molar enthalpies of reaction of metallic barium with 0.047 mol·dm−3 HClO4 as well as the molar enthalpies of dissolution of BaCl2 in 1.01 mol·dm−3 HCl and in water have been measured at T=298.15 K in a sealed swinging calorimeter with an isothermal jacket. From these results the standard molar enthalpy of formation of the barium ion in an aqueous solution at infinite dilution, as well as the enthalpies of formation of barium chloride and barium perchlorate, are calculated to be: ΔfH0m(Ba2+,aq)=−(535.83±1.25) kJ · mol−1; ΔfH0m(BaCl2,cr)=−(855.66±1.28) kJ · mol−1; and ΔfH0m(BaClO4,cr)=−(796.26±1.35) kJ · mol−1. The results obtained are discussed and compared with previous experimental values. 相似文献
8.
《The Journal of chemical thermodynamics》2007,39(3):455-461
Three members of the lead (II) n-alkanoates (from etanoate to n-butanoate) have been synthesized, purified and studied by d.s.c., X-ray diffraction, and FTIR spectroscopy. Lead (II) acetate, propanoate, and butanoate present only a melting transition at T = (452.6, 398.2, and 346.5) K, with ΔfH = (16.0, 13.1, and 15.6) kJ · mol−1, and ΔfS = (35.3, 32.8, and 45.1) J · mol−1 · K−1, respectively. These temperature data correct to a great extent the historical values reported in the literature. These three members readily quench into a glass state. Their corresponding Tg values are (314.4, 289.0, and 274.9) K, respectively, measured by d.s.c. at a heating rate of 5 K · min−1. 相似文献
9.
The conformation surface of tris(2-methylbenzimidazol-1-yl)methane has been explored locating four minima (uuu, uud, udd and ddd, each one corresponding to two enantiomers, the P and the M) and seven transition states. The known experimental barrier to racemization (119 kJ mol?1) was calculated to be about 110 kJ mol?1 (uuu or uud stereoisomers). GIAO calculations of absolute shieldings correlate very well with 1H and 13C NMR chemical shifts. Finally, the specific rotation of the four minima was calculated allowing us to identify the absolute configuration of the first eluted enantiomer. 相似文献
10.
《Polyhedron》2005,24(16-17):2269-2273
Two ion-pair compounds, consisting of 1-(4′-R-benzyl)pyridinium ([RBzPy]+, R = NO2 (1) and Br (2)) and [Ni(dmit)2]− (dmit2− = 2-thioxo-1,3-dithion-4,5-dithiolato), have been synthesized and structurally characterized. The anions of [Ni(dmit)2]− stack into dimers, which further construct into two-leg ladder through terminal S⋯S interactions in 1, lateral S⋯S interactions in 2. The weak H-bonding interactions of C–H⋯S were observed in 2, while only weak van de Waals interactions between anion and cations in 1. The magnetic susceptibilities measured in 2–300 K indicate AFM exchange interaction domination both two compounds. A peculiar magnetic transition at ∼100 K was observed in 1. An AFM ordering below ∼11 K was found in 2, and the best fit to magnetic susceptibility above 45 K in this compound, using a dimer model with s = 1/2, give rise to Δ/kB = 36.1 K, zJ = −0.91 K, C = 3.2 × 10−3 emu K mol−1 and χ0 = −4.0 × 10−6 emu mol−1 with g of 2.0 fixed. 相似文献
11.
《Journal of organometallic chemistry》2005,690(24-25):6089-6095
A series of cationic Rh(I) carbonyl complexes of the form [Rh(CO)(L)]PF6 (where L = 2,6-bis (alkylimidazol-2-ylidene)-pyridine; alkyl = Me (1a), Et (1b), CH2Ph (1c)) have been prepared by the reactions of [Rh(CO)2(OAc)]2 with diimidazolium pyridine salts in the presence of NEt3. The ν(CO) values for 1 are ca. 1982 cm−1, indicating that the N-heterocyclic carbene ligands impart high electron density on the Rh(I) centres, despite the overall cationic charge. Each of the Rh(I) complexes reacts with MeI to form two isomeric Rh(III) methyl species, and a third unidentified species. Kinetic measurements on the MeI oxidative addition reactions give second-order rate constants (MeCN, 25 °C) of 0.0927, 0.0633 and 0.0277 M−1 s−1 for 1a, 1b and 1c, respectively. Comparison of these data with those for related Rh(I) carbonyl complexes shows that 1 have remarkably high nucleophilicity for cationic species. 相似文献
12.
《The Journal of chemical thermodynamics》2004,36(11):929-937
Measurements of vapour pressure in the liquid phase and of enthalpy of vaporisation and results of calculation of ideal-gas properties for diethyl phthalate are reported. The method of comparative ebulliometry, the static method, and the Knudsen mass-loss effusion method were employed to determine the vapour pressure. A Calvet-type differential microcalorimeter was used to measure the enthalpy of vaporisation. Simultaneous correlation of vapour pressure, of enthalpy of vaporisation and of difference in heat capacities of ideal gas and liquid/solid phases was used to generate parameters of the Cox equation that cover both the (vapour + solid) equilibrium (approximate temperature range from 220 K to 270 K) and (vapour + liquid) equilibrium (from 270 K to 520 K). Vapour pressure and enthalpy of vaporisation derived from the fit are reported at the triple-point temperature T = 269.92 K (p = 0.0029 Pa, ΔvapHm = 85.10 kJ · mol−1 ), at T = 298.15 K (p = 0.099 Pa, ΔvapHm = 82.09 kJ · mol−1), and at the normal boiling temperature T = 570.50 K (ΔvapHm = 56.49 kJ · mol−1). Measured vapour pressures and measured and calculated enthalpies of vaporisation are compared with literature data. 相似文献
13.
《The Journal of chemical thermodynamics》2003,35(8):1361-1381
Microcalorimetry, spectrophotometry, and high-performance liquid chromatography (h.p.l.c.) have been used to conduct a thermodynamic investigation of the glutathione reductase catalyzed reaction {2 glutathionered(aq) + NADPox(aq)=glutathioneox(aq) + NADPred(aq)}. The reaction involves the breaking of a disulfide bond and is of particular importance because of the role glutathionered plays in the repair of enzymes. The measured values of the apparent equilibrium constant K′ for this reaction ranged from 0.5 to 69 and were measured over a range of temperature (288.15 K to 303.15 K), pH (6.58 to 8.68), and ionic strength Im (0.091 mol · kg−1 to 0.90 mol · kg−1). The results of the equilibrium and calorimetric measurements were analyzed in terms of a chemical equilibrium model that accounts for the multiplicity of ionic states of the reactants and products. These calculations led to values of thermodynamic quantities at T=298.15 K and Im=0 for a chemical reference reaction that involves specific ionic forms. Thus, for the reaction {2 glutathionered−(aq) + NADPox3−(aq)=glutathioneox2−(aq) + NADPred4−(aq) + H+(aq)}, the equilibrium constant K=(6.5±4.4)·10−11, the standard molar enthalpy of reaction ΔrHom=(6.9±3.0) kJ · mol−1, the standard molar Gibbs free energy change ΔrGom=(58.1±1.7) kJ · mol−1, and the standard molar entropy change ΔrSom=−(172±12) J · K−1 · mol−1. Under approximately physiological conditions (T=311.15 K, pH=7.0, and Im=0.25 mol · kg−1 the apparent equilibrium constant K′≈0.013. The results of the several studies of this reaction from the literature have also been examined and analyzed using the chemical equilibrium model. It was found that much of the literature is in agreement with the results of this study. Use of our results together with a value from the literature for the standard electromotive force Eo for the NADP redox reaction leads to Eo=0.166 V (T=298.15 K and I=0) for the glutathione redox reaction {glutathioneox2−(aq) + 2 H+(aq) + 2 e−=2 glutathionered−(aq)}. The thermodynamic results obtained in this study also permit the calculation of the standard apparent electromotive force E′o for the biochemical redox reaction {glutathioneox(aq) + 2 e−=2 glutathionered(aq)} over a wide range of temperature, pH, and ionic strength. At T=298.15 K, I=0.25 mol · kg−1, and pH=7.0, the calculated value of E′o is −0.265 V. 相似文献
14.
《Radiation Physics and Chemistry》2004,69(3):211-216
The temperature dependence of the rate constant for the reactions of HO2 with OH, H, Fe2+ and Cu2+ has been determined using pulse radiolysis technique. The following rate constants, k (dm3 mol−1 s−1) at 20°C and activation energies, Ea (kJ mol−1) have been found. The reaction with OH was studied in the temperature range 20–296°C (k=7.0×109, Ea=7.4) and the reaction with H in the temperature range 5–149°C (k=8.5×109, Ea=17.5). The reaction with Fe2+ was studied in the temperature range 16–118°C (k=7.9×105, Ea=36.8) and the reaction with Cu2+ in the temperature range 17–211°C (k=1.1×108, Ea=14.9). 相似文献
15.
《The Journal of chemical thermodynamics》2003,35(9):1469-1487
Standard values of Gibbs free energy, entropy, and enthalpy of Na2Ti6O13 and Na2Ti3O7 were determined by evaluating emf-measurements of thermodynamically defined solid state electrochemical cells based on a Na–β″-alumina electrolyte. The central part of the anodic half cell consisted of Na2CO3, while two appropriate coexisting phases of the ternary system Na–Ti–O are used as cathodic materials. The cell was placed in an atmosphere containing CO2 and O2. By combining the results of emf-measurements in the temperature range of 573⩽T/K⩽1023 and of adiabatic calorimetric measurements of the heat capacities in the low-temperature region 15⩽T/K⩽300, the thermodynamic data were determined for a wide temperature range of 15⩽T/K⩽1100. The standard molar enthalpy of formation and standard molar entropy at T=298.15 K as determined by emf-measurements are ΔfHm0=(−6277.9±6.5) kJ · mol−1 and Sm0=(404.6±5.3) J · mol−1 · K−1 for Na2Ti6O13 and ΔfHm0=(−3459.2±3.8) kJ · mol−1 and Sm0=(227.8±3.7) J · mol−1 · K−1 for Na2Ti3O7. The standard molar entropy at T=298.15 K obtained from low-temperature calorimetry is Sm0=399.7 J · mol−1 · K−1 and Sm0=229.4 J · mol−1 · K−1 for Na2Ti6O13 and Na2Ti3O7, respectively. The phase widths with respect to Na2O content were studied by using a Na2O-titration technique. 相似文献
16.
《Journal of Analytical and Applied Pyrolysis》2009,84(2):145-150
The thermal behavior of 4-amino-1,2,4-triazol-5-one (ATO) was studied under non-isothermal condition by DSC method in a sealed cell of stainless steel. The melting enthalpy and melting entropy of ATO are 21.34 ± 0.49 kJ mol−1 and 46.54 ± 0.30 J mol−1 K−1, respectively. The kinetic parameters were obtained from the analysis of DSC curves by Kissinger method, Ozawa method, the differential method and the integral method. The main exothermic decomposition reaction mechanism of ATO is classified as nucleation and growth, and the kinetic parameters of the reaction are Ea = 119.50 kJ mol−1 and A = 109.03 s−1. The gas products and condensed phase products of the thermal decomposition of ATO were studied on two simultaneous devices of the fast thermolysis reaction cell (gas reaction cell) in situ in conjunction with rapid scan transform infrared spectroscopy (RSFT-IR) and the solid reaction cell in situ. The heat of formation (HOF) for ATO was evaluated by G3 theory. The detonation velocity (D) and detonation pressure (P) were estimated by using the well-known Kamlet–Jacobs equation, based on the theoretical HOF and the determined crystal density. 相似文献
17.
Hydroboration reactions of 4-octene with HBBr2 · SMe2, HBCl2 · SMe2 and H2BBr · SMe2 in CH2Cl2 were studied as function of concentration and temperature and compared with those of 1-octene. On average, hydroboration with dihaloborane proceeded 16 times slower for 4-octene than for 1-octene. In the case of the reactions with the monohaloborane, this factor is halved. This can be explained by the difference in the relative rates of dissociates of Me2S from the dihaloborane and a monohaloborane complex, respectively. The reactions involving H2BBr · SMe2 also exhibited a k?2 value, an indication of the presence of a parallel reaction, most likely a rearrangement process facilitating isomerization by way of a π-complex. The moderate ΔH≠ values accompanied by small ΔS≠ values (94 ± 4 kJ mol?1, ?3 ± 13 J K?1 mol?1 for HBBr2 · SMe2; 93 ± 1 kJ mol?1, ?17 ± 4 J K?1 mol?1 for HBCl2 · SMe2 and in the case of H2BBr · SMe2, 90 ± 13 kJ mol?1, +12 ± 44 J K?1 mol?1 and 83 ± 13 kJ mol?1, ?24 ± 45 J K?1 mol?1, respectively, for the k2 and k?2 processes) imply a process that is dissociatively dominated, with the overall mode of activation being interchange dissociative (Id). 相似文献
18.
《Tetrahedron: Asymmetry》2014,25(9):744-749
Phosphine–phosphites 3a and 3b, derived from diphenylhydroxymethyl phosphine have been prepared. From these ligands [Rh(COD)(3a)]BF4 5a and RuCl2(3b)[(S,S)-DPEN] 6b (DPEN = 1,2-diphenylethylenediamine) were synthesized and their structure determined by X-ray diffraction. Ligands 3 are characterized by a small bite angle of 83°. In addition, 5a led to an active catalyst for the hydrogenation of olefins, giving enantioselectivities of up to 96% ee. Likewise, compound 6b showed good activity and enantioselectivity in the hydrogenation of N-1-phenyl ethylidene aniline and a completed reaction at S/C = 500 in 24 h with 83% ee. 相似文献
19.
The energetic study of 4-nitro-2,1,3-benzothiadiazole has been developed using experimental techniques together with computational approaches. The standard (p° = 0.1 MPa) molar enthalpy of formation of crystalline 4-nitro-2,1,3-benzothiadiazole (181.9 ± 2.3 kJ · mol−1) was determined from the experimental standard molar energy of combustion −(3574.3 ± 1.3) kJ · mol−1, in oxygen, measured by rotating-bomb combustion calorimetry at T = 298.15 K. The standard (p° = 0.1 MPa) molar enthalpy of sublimation, at T = 298.15 K, (101.8 ± 4.3) kJ · mol−1, was determined by a direct method, using the vacuum drop microcalorimetric technique. From the latter value and from the enthalpy of formation of the solid, it was calculated the standard (p° = 0.1 MPa) enthalpy of formation of gaseous 4-nitro-2,1,3-benzothiadiazole as (283.7 ± 4.9) kJ · mol−1. Standard ab initio molecular orbital calculations were performed using the G3(MP2)//B3LYP composite procedure and several working reactions in order to derive the standard molar enthalpy of formation 4-nitro-2,1,3-benzothiadiazole. The ab initio results are in good agreement with the experimental data. 相似文献
20.
《Polyhedron》2007,26(9-11):2101-2104
The bimetallic ferromagnetic chain {[K(18-crown-6)][Mn(bpy)Cr(ox)3]}∞ (1) has been synthesized and characterized. It crystallizes in the orthorhombic chiral space group P212121 [a = 9.0510(2) Å, b = 14.4710(3) Å, c = 26.8660(8) Å, V = 3510.97(1) Å3, Z = 2]. Compound 1 is made up by anionic [Mn(bpy)Cr(ox)3]− 1D chains and cationic [K(18-crown-6)]+ complexes. The magnetic exchange within the chain is ferromagnetic [J = +7.8(7) cm−1]. In the solid state, the ferromagnetic chains are well isolated magnetically and no long range magnetic ordering has been observed above 2 K. 相似文献