Thermodynamic properties of CaTiF5(s)

Calcium titanofluoride CaTiF₅(s) was prepared by solid-state reaction of CaF₂(s) with TiF₃(s) and characterized by X-ray diffraction method. The standard molar isobaric heat capacity $(C_{p\text{,m}}^{\circ })$ of CaTiF₅(s) was determined by a power compensated differential scanning calorimeter in the temperature from 230 K to 710 K. A solid-state galvanic cell with CaF₂ as electrolyte was used to determine the standard molar Gibbs energy of formation $({\mathrm{\Delta }}_{\text{f}}{G}_{\text{m}}^{\circ })$ of CaTiF₅ in the temperature range from 803 K to 1005 K. The galvanic cell can be depicted as:$(-)\text{Pt,}{\text{O}}_2(\text{g,}101.325\text{kPa})/\{\text{CaO(s)}+{\text{CaF}}_2(\text{s})\}//{\text{CaF}}_2//\{{\text{CaTiF}}_5(\text{s})+{\text{CaTiO}}_3(\text{s})\}/{\text{O}}_2(\text{g,}101.325\text{kPa})\text{,Pt}(+)$The second law analysis of present data were carried out to derive the standard entropy $S_{\text{m}}^{\circ }(298.15\text{K})$ and the enthalpy of formation ${\mathrm{\Delta }}_{\text{f}}{H}_{\text{m}}^{\circ }(298.15\text{K})$ and the values derived are 68.7 J · K⁻¹ · mol⁻¹ and −2848.4 kJ · mol⁻¹, respectively.     

Dioxygen affinities and catalytic oxidation performance of cobalt（Ⅱ） hydroxamates with benzo-15-crown-5 pendants

The oxygenation constants(Ko_2)of cobalt(Ⅱ)hydroxamates(CoL_2~1-CoL_2~3)with benzo-15-crown-5(B15C5)pendants were measured over the range of-5 to 20℃,and the values of thermodynamic parameters(ΔH~0 andΔS~0)were calculated based on these(No_2)values.Meanwhile,these crowned complexes were employed to the oxidation for p-xylene to p-toluic acid with air at 110Δunder normal atmospheric pressure.The effects of B15C5 pendant and the length of chain bonded to B15C5 in these complexes on the O_2-binding capabilities and oxidation for p-xylene were investigated with the comparison of crown-free analogues CoL_2~4.     

A thermodynamic study of ketoreductase-catalyzed reactions 4. Reduction of 2-substituted cyclohexanones in n-hexane

The equilibrium constants K for the ketoreductase-catalyzed reduction reactions (2-substituted cyclohexanone + 2-propanol = cis- and trans-2-substituted cyclohexanol + acetone) have been measured in n-hexane as solvent. The 2-substituted cyclohexanones included in this study are: 2-methylcyclohexanone, 2-phenylcyclohexanone, and 2-benzylcyclohexanone. The equilibrium constants K for the reactions with 2-methylcyclohexanone were measured over the range T = 288.15 to 308.05 K. The thermodynamic quantities at T = 298.15 K are: K = (2.13 ± 0.06); ${\mathrm{\Delta }}_{\text{r}}{G}_{\text{m}}^{\circ }=-(1.87\pm 0.06)\text{kJ}·{\text{mol}}^{-1}$; ${\mathrm{\Delta }}_{\text{r}}{H}_{\text{m}}^{\circ }=-(6.56\pm 2.68)\text{kJ}·{\text{mol}}^{-1}$; and ${\mathrm{\Delta }}_{\text{r}}{S}_{\text{m}}^{\circ }=-(15.7\pm 9.2)\text{J}·{\text{K}}^{-1}·{\text{mol}}^{-1}$ for the reaction involving cis-2-methylcyclohexanol, and K = (10.7 ± 0.2); ${\mathrm{\Delta }}_{\text{r}}{G}_{\text{m}}^{\circ }=-(5.87\pm 0.04)\text{kJ}·{\text{mol}}^{-1}$; ${\mathrm{\Delta }}_{\text{r}}{H}_{\text{m}}^{\circ }=-(2.54\pm 1.8)\text{kJ}·{\text{mol}}^{-1}$; and ${\mathrm{\Delta }}_{\text{r}}{S}_{\text{m}}^{\circ }=(11.2\pm 6.4)\text{J}·{\text{K}}^{-1}·{\text{mol}}^{-1}$ for the reaction involving trans-2-methylcyclohexanol. The standard molar Gibbs free energy changes ${\mathrm{\Delta }}_{\text{r}}{G}_{\text{m}}^{\circ }$ for the reactions (trans-2-substituted cyclohexanol = cis-2-substituted cyclohexanol) in n-hexane have also been calculated and compared with the literature data that pertain to reactions in the gas phase and at higher temperatures. Experiments carried out with a chiral column demonstrated that the enzymatic reduction of 2-phenylcyclohexanone catalyzed by the ketoreductase used in this study is not stereoselective.     

Standard state thermodynamic properties of aqueous sodium perrhenate using high dilution calorimetry up to 598.15 K

Standard state thermodynamic properties for aqueous sodium perrhenate at temperature in the range of (298.15 to 598.15) K and at p_sat were determined by high dilution solution calorimetry down to 10^?4 m. Standard state partial molar heat capacities, $C_{p\text{,}2}^{°}$, of aqueous sodium perrhenate calculated from present study are compared to literature values up to T = 398.15 K. The differences between $C_{p\text{,}2}^{°}$ of ${\text{ReO}}_4^{-}(\text{aq})$ and Cl^?(aq) at lower temperature is much greater than that due to their internal molecular motions. Consequently, the perrhenate ion appears to have an ionic incomplete primary hydration shell as compared to the chloride ion. The ${\text{ReO}}_4^{-}/{\text{Cl}}^{-}$ difference in thermodynamic functions has now been well defined up to T = 598.15 K for other important high temperature calculations.