Thermochemistry of 2,2′-dipyridil N-oxide and 2,2′-dipyridil N,N′-dioxide. The dissociation enthalpies of the N−O bonds

In this paper, the first, second and mean (N?O) bond dissociation enthalpies (BDEs) were derived from the standard (p° = 0.1 MPa) molar enthalpies of formation, in the gaseous phase, ${\mathrm{\Delta }}_{\text{f}}{H}_{\text{m}}^{°}(\text{g})$, at T = 298.15 K, of 2,2′-dipyridil N-oxide and 2,2′-dipyridil N,N′-dioxide. These values were calculated from experimental thermodynamic parameters, namely from the standard (p° = 0.1 MPa) molar enthalpies of formation, in the crystalline phase, ${\mathrm{\Delta }}_{\text{f}}{H}_{\text{m}}^{°}(\text{cr})$, at T = 298.15 K, obtained from the standard molar enthalpies of combustion, ${\mathrm{\Delta }}_{\text{c}}{H}_{\text{m}}^{°}$, measured by static bomb combustion calorimetry, and from the standard molar enthalpies of sublimation, at T = 298.15 K, determined from Knudsen mass-loss effusion method.     

Physicochemical investigation of the clouding behavior and thermodynamics of p-tert-alkylphenoxy poly (oxyethylene) ether micelles in aqueous environment and in the presence of diols

Cloud point (CP) measurements of nonionic surfactant namely p-tert-alkylphenoxy poly (oxyethylene) ether (TX-100) were carried out in the absence and presence of organic additives such as diols (1,2-ethanediol; 1,2-propanediol and 2,3-butanediol) and polyols (glycerol, glucose, fructose and sorbitol). For (diol + TX-100 + water) system, cloud points (CP) were found to be increased with the increase in concentration of diols for both (4 and 10)% TX-100 solutions and found to follow the order: CP_{1,2-propanediol} > CP_{2,3-butanediol} > CP_{1,2-ethanediol}. For (polyols + TX-100 + water) system, the depression of cloud point (CP) was observed with increase of polyol concentrations for both (4 and 10)% of TX-100 solutions and the trend almost follows the order: CP_glycerol < CP_glucose < CP_fructose < CP_sorbitol. The values of $\mathrm{\Delta }{G}_{\text{c}}°$ were found to be positive for all the systems studied. The $\mathrm{\Delta }{H}_{\text{c}}°$ and $\mathrm{\Delta }{S}_{\text{c}}°$ values were found to be positive in the presence of diols while those were found to be almost negative in the presence of polyols during clouding of TX-100.     

Synthesis,structure, and thermodynamics of a lanthanide coordination compound incorporating 5-nitroisophthalic acid

A lanthanide coordination compound, [Sm₃(5-nip)₄(5-Hnip)(H₂O)₇·9H₂O]_n (5-H₂nip = 5-nitroisophthalic acid), has been synthesized and characterized by elemental analysis, IR, TG-DSC, and single-crystal X-ray diffraction. Structural analysis reveals that the compound features two kinds of 1D channels with guest water molecules. TG-DSC curves show that the dehydrated product of the compound exhibits high stability up to 673 K. The enthalpy change of reaction of formation in water, ${\mathrm{\Delta }}_{\text{r}}{H}_{\text{m}}^{\theta }$(l), was determined to be (27.608 ± 0.133) kJ · mol⁻¹ at (298.15 ± 0.01) K by microcalorimetry. Based on a designed thermochemical cycle and other auxiliary thermodynamic data, the enthalpy change of reaction of formation in solid at (298.15 ± 0.01) K and the standard molar enthalpy for the compound, ${\mathrm{\Delta }}_{\text{r}}{H}_{\text{m}}^{\theta }$(s) and ${\mathrm{\Delta }}_{\text{f}}{H}_{\text{m}}^{\theta }$, were calculated to be (96.8 ± 0.8) kJ · mol⁻¹ and (−831.4 ± 16.0) kJ · mol⁻¹, respectively. In addition, thermodynamics and thermokinetics of the reaction of formation of the compound were investigated in water.     

Heat capacity and thermodynamic functions of nano-TiO2 rutile in relation to bulk-TiO2 rutile

Several conflicting reports have suggested that the thermodynamic properties of materials change with respect to particle size. To investigate this, we have measured the constant pressure heat capacities of three 7 nm TiO₂ rutile samples containing varying amounts of surface-adsorbed water using a combination of adiabatic and semi-adiabatic calorimetric methods. These samples have a high degree of chemical, phase, and size purity determined by rigorous characterization. Molar heat capacities were measured from T = (0.5 to 320) K, and data were fitted to a sum of theoretical functions in the low temperature (T < 15 K) range, orthogonal polynomials in the mid temperature range (10 > T/K > 75), and a combination of Debye and Einstein functions in the high temperature range (T > 35 K). These fits were used to generate $\mathit{Cp}\text{,}{\text{m}}^{\circ }$, ${\mathrm{\Delta }}_0^{\text{T}}{S}_{\text{m}}^{\circ }$, ${\mathrm{\Delta }}_0^{\text{T}}{H}_{\text{m}}^{\circ }$, and ${\phi }_{\text{m}}^{\circ }$ values at selected temperatures between (0.5 and 300) K for all samples. Standard molar entropies at T = 298.15 K were calculated to be (62.066, 59.422, and 58.035) J · K⁻¹ · mol⁻¹ all with a standard uncertainty of 0.002·${\mathrm{\Delta }}_0^{\text{T}}{S}_{\text{m}}^{\circ }$ for samples TiO₂·0.361H₂O, TiO₂·0.296H₂O, and TiO₂·0.244H₂O, respectively. These and other thermodynamic values were then corrected for water content to yield bare nano-TiO₂ thermodynamic properties at T = 298.15 K, and we show that the resultant thermodynamic properties of anhydrous TiO₂ rutile nanoparticles equal those of bulk TiO₂ rutile within experimental uncertainty. Thus we show quantitatively that the difference in thermodynamic properties between bulk and nano-TiO₂ must be attributed to surface adsorbed water.