The solubility measurements of sodium dicarboxylate salts; sodium oxalate,malonate, succinate,glutarate, and adipate in water from T = (279.15 to 358.15) K

The solubility measurements of sodium dicarboxylate salts; sodium oxalate, malonate, succinate, glutarate, and adipate in water at temperatures from (278.15 to 358.15 K) were determined. The molar enthalpies of solution at T = 298.15 K were derived: Δ_solH_m (m = 2.11 mol · kg^?1) = 13.86 kJ · mol^?1 for sodium oxalate; Δ_solH_m (m = 3.99 mol · kg^?1) = 14.83 kJ · mol^?1 for sodium malonate; Δ_solH_m (m = 2.45 mol · kg^?1) = 14.83 kJ · mol^?1 for sodium succinate; Δ_solH_m (m = 4.53 mol · kg^?1) = 16.55 kJ · mol^?1 for sodium glutarate, and Δ_solH_m (m = 3.52 mol · kg^?1) = 15.70 kJ · mol^?1 for sodium adipate. The solubility value exhibits a prominent odd–even effect with respect to terms with odd number of sodium dicarboxylate carbon numbers showing much higher solubility. This odd–even effect may have implications for the relative abundance of these compounds in industrial applications and also in the atmospheric aerosols.     

Energetic effects of ether and ketone functional groups in 9,10-dihydroanthracene compound

The energetic effects caused by replacing one of the methylene groups in the 9,10-dihydroanthracene by ether or ketone functional groups yielding xanthene and anthrone species, respectively, were determined from direct comparison of the standard (p° = 0.1 MPa) molar enthalpies of formation in the gaseous phase, at T = 298.15 K, of these compounds. The experimental static-bomb combustion calorimetry and Calvet microcalorimetry and the computational G3(MP2)//B3LYP method were used to get the standard molar gas-phase enthalpies of formation of xanthene, (41.8 ± 3.5) kJ · mol^?1, and anthrone, (31.4 ± 3.2) kJ · mol^?1. The enthalpic increments for the substitution of methylene by ether and ketone in the parent polycyclic compound (9,10-dihydroanthracene) are ?(117.9 ± 5.5) kJ · mol^?1 and ?(128.3 ± 5.4) kJ · mol^?1, respectively.     

Heat capacity and thermodynamic properties of germanium disulfide at temperatures from T = (2 to 1240) K

The heat capacity of polycrystalline germanium disulfide α-GeS₂ has been measured by relaxation calorimetry, adiabatic calorimetry, DSC and heat flux calorimetry from T = (2 to 1240) K. Values of the molar heat capacity, standard molar entropy and standard molar enthalpy are 66.191 J · K^?1 · mol^?1, 87.935 J · K^?1 · mol^?1 and 12.642 kJ · mol^?1. The temperature of fusion and its enthalpy change are 1116 K and 23 kJ · mol^?1, respectively. The thermodynamic functions of α-GeS₂ were calculated over the range (0 ? T/K ? 1250).     

The removal of uranium (VI) from aqueous solutions onto natural sepiolite

The adsorption of uranium (VI) from aqueous solutions onto natural sepiolite has been studied using a batch adsorber. The parameters that affect the uranium (VI) sorption, such as contact time, solution pH, initial uranium(VI) concentration, and temperature, have been investigated and optimized conditions determined. Equilibrium isotherm studies were used to evaluate the maximum sorption capacity of sepiolite and experimental results showed this to be 34.61 mg · g^?1. The experimental results were correlated reasonably well by the Langmuir adsorption isotherm and the isotherm parameters (Q_o and b) were calculated. Thermodynamic parameters (ΔH° = ?126.64 kJ · mol^?1, ΔS° = ?353.84 J · mol^?1 · K^?1, ΔG° = ?21.14 kJ · mol^?1) showed the exothermic heat of adsorption and the feasibility of the process. The results suggested that sepiolite was suitable as sorbent material for recovery and adsorption of uranium (VI) ions from aqueous solutions.     

The role of the double bond position in hydroboration using HBBr2 · SMe2, HBCl2 · SMe2 and H2BBr · SMe2: A detailed kinetic and mechanistic study

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 (I_d).     

Standard molar enthalpies of formation of 2-furancarbonitrile, 2-acetylfuran,and 3-furaldehyde

The standard (p^° = 0.1 MPa) molar energies of combustion of 2-furancarbonitrile, 2-acetylfuran, and 3-furaldehyde were measured by static bomb combustion calorimetry; the Calvet high-temperature microcalorimetry was used to measure the enthalpies of vaporization of these liquid compounds. The standard molar enthalpies of formation of the three compounds, in the gaseous phase, at T = 298.15 K, have been derived from the corresponding standard molar enthalpies of formation in the liquid phase and the standard molar enthalpies of phase transition, as (106.8 ± 1.1) kJ · mol^?1, ?(207.4 ± 1.3) kJ · mol^?1, and ?(151.9 ± 1.1) kJ · mol^?1, for 2-furancarbonitrile, 2-acetylfuran, and 3-furaldehyde, respectively.Standard molar enthalpies of formation are discussed in terms of the isomerization ortho meta. Enthalpic increment values of the introduction of the functional groups –CN, –CHO, and –COCH₃ were also compared with some other heterocycles; i.e. thiophene and pyridine.     

Determination of the energies of combustion and enthalpies of formation of nitrobenzenesulfonamides by rotating-bomb combustion calorimetry

The energies of combustion for 2-nitrobenzenesulfonamide (cr), 3-nitrobenzenesulfonamide (cr), and 4-nitrobenzenesulfonamide (cr) were determined using a recently described rotating-bomb combustion calorimeter. The condensed phase molar energies of combustion obtained were ?(3479.2 ± 1.0) kJ · mol^?1 for 2-nitrobenzenesulfonamide (cr), ?(3454.2 ± 1.1) kJ · mol^-1 for 3-nitrobenzenesulfonamide (cr), and ?(3450.1 ± 1.9) kJ · mol^-1 for 4-nitrobenzenesulfonamide (cr). From these combustion energy values, the standard molar enthalpies of formation in the condensed phase were obtained as: ?(341.3 ± 1.3) kJ · mol^?1, ?(366.3 ± 1.3) kJ · mol^?1, and ?(370.4 ± 2.1) kJ · mol^?1, respectively. Polyethene bags were used as an auxiliary material in the combustion experiments. The heat capacities and purities of the compounds were determined using a differential scanning calorimeter.     

Energetic studies of urea derivatives: Standard molar enthalpy of formation of 3,4,4′-trichlorocarbanilide

Thermochemical and thermophysical studies have been carried out for crystalline 3,4,4′-trichlorocarbanilide. The standard (p° = 0.1 MPa) molar enthalpy of formation, at T = 298.15 K, for the crystalline 3,4,4′-trichlorocarbanilide (TCC) was experimentally determined using rotating-bomb combustion calorimetry, as ?(234.6 ± 8.3) kJ · mol^?1. The standard enthalpy of sublimation, at the reference temperature of 298.15 K, was measured by the vacuum drop microcalorimetric technique, using a High Temperature Calvet Microcalorimeter as (182.1 ± 1.7) kJ · mol^?1. These two thermochemical parameters yielded the standard molar enthalpy of formation of the studied compound, in the gaseous phase, at T = 298.15 K, as ?(52.5 ± 8.5) kJ · mol^?1. This parameter was also calculated by computational thermochemistry at M05-2X/6-311++G7 and B3LYP/6-311++G(3df, 2p) levels, with a deviation less than 4.5 kJ · mol^?1 from experimental value. Moreover, the thermophysical study was made by differential scanning calorimetry, DSC, over the temperature interval between T = 263 K and its onset fusion temperature, T = (527.5 ± 0.4) K. A solid–solid phase transition was found at T = (428 ± 1) K, with the enthalpy of transition of (6.1 ± 0.1) kJ · mol^?1. The X-ray crystal structure of TCC was determined and the three-centred N–H?OC hydrogen bonds present analyzed.     

Thermodynamic properties of metal amides determined by ammonia pressure-composition isotherms

Thermodynamic properties of Mg(NH₂)₂ and LiNH₂ were investigated by measurements of NH₃ pressure-composition isotherms (PCI). Van’t Hoff plot of plateau pressures of PCI for decomposition of Mg(NH₂)₂ indicated the standard enthalpy and entropy change of the reactions were ΔH° = (120 ± 11) kJ · mol^?1 (per unit amount of NH₃) and ΔS° = (182 ± 19) J · mol^?1 · K^?1 for the reaction: Mg(NH₂)₂ → MgNH + NH₃, and ΔH° = 112 kJ · mol^?1 and ΔS^o = 157 J · mol^?1 · K^?1 for the reaction: MgNH → (1/3)Mg₃N₂ + (1/3)NH₃. PCI measurements for formation of LiNH₂ were carried out, and temperature dependence of plateau pressures indicated ΔH° = (?108 ± 15) kJ · mol^?1 and ΔS° = (?143 ± 25) J · mol^?1 · K^?1 for the reaction: Li₂NH + NH₃ → 2LiNH₂.     

Thermodynamic characterization of NiAl

Thermodynamic properties of the high-stability intermetallic compound nickel aluminide, NiAl, have been determined from mass-spectrometric, weight-loss effusion, and calorimetric measurements, using samples from a single preparation with a composition determined to be Ni_0.986Al_1.014. Per mole of NiAl molecules, the specific heat capacity at room temperature of 298 K is 48.54 J · K^?1 · mol^?1, with a linear temperature dependence of +0.0104 J · K^?2 · mol^?1. At the same temperature, the enthalpy of formation is ?133.7 kJ · mol^?1, the entropy is about 53.8 J · K^?1 · mol^?1 and the enthalpy difference between room temperature and absolute zero is 7.97 kJ · mol^?1. The Gibbs free-energy is ?130.2 kJ · mol^?1 at T = 298 K, with a linear temperature dependence of +5.04 J · K^?1 · mol^?1. The Debye temperature is 452 K, while the electronic density-of-states at the Fermi-level is about 0.29 states per eV-atom. The NiAl⁺ ions were observed in the high-temperature mass spectra. Pressures for the gas at these temperatures were estimated and used with the results of quantum-mechanical calculations of total energy, specific heat, and entropy to calculate free-energy functions for the gas. These and additional results are compared with other measurements and discussed in terms of current theories of the electronic and structural properties of the compound.     

Thermochemical study of some methoxytetralones

The standard (p^° = 0.1 MPa) molar energies of combustion in oxygen, at T = 298.15 K, of 5-, 6- and 7-methoxy-α-tetralone were measured by static bomb calorimetry. The values of the standard molar enthalpies of sublimation were obtained by Calvet microcalorimetry and corrected to T = 298.15 K. Combining these results, the standard molar enthalpies of formation of the compounds, in the gas phase, at T = 298.15 K, have been calculated, 5-methoxy-α-tetralone -(244.8 ± 1.9) kJ · mol^?1, 6-methoxy-α-tetralone ?(243.0 ± 2.8) kJ · mol^?1 and 7-methoxy-α-tetralone ?(242.3 ± 2.6) kJ · mol^?1.Additionally, high-level density functional theory calculations using the B3LYP hybrid exchange–correlation energy functional with extended basis sets and more accurate correlated computational techniques of the MCCM/3 suite have been performed for the compounds. The agreement between experiment and theory gives confidence to estimate the enthalpy of formation of 8-methoxy-α-tetralone. Similar calculations were done for the 5-, 6-, 7- and 8-methoxy-β-tetralone, for which experimental work was not done.     

Thermodynamic analysis of sorption isotherms of chromium(VI) anionic species on reed biomass

A new sorbent material for removing Cr(VI) anionic species from aqueous solutions has been investigated. Adsorption equilibrium and thermodynamics of Cr(VI) anionic species onto reed biomass were studied at different initial concentrations, sorbent concentrations, pH levels, temperatures, and ionic strength. Equilibrium isotherm was analyzed by Langmuir model. The experimental sorption data fit the model very well. The maximum sorption capacity of Cr(VI) onto reed biomass was found to be 33 mg · g^?1. It was noted that the Cr(VI) adsorption by reed biomass decreased with increase in pH. An increase in temperature resulted in a higher Cr(VI) loading per unit weight of the adsorbent. Removal of Cr(VI) by reed biomass seems to be mainly by chemisorption. The change in entropy (ΔS^°) and heat of adsorption (ΔH^°) for Cr(VI) adsorption on reed biomass were estimated as 2205 kJ · kg^?1 · K^?1 and 822 kJ · kg^?1, respectively. The values of isosteric heat of adsorption varied with the surface loading of Cr(VI).     

3,4,5-Trimethoxyphenol: A combined experimental and theoretical thermochemical investigation of its antioxidant capacity

The standard (p^° = 0.1 MPa) molar enthalpies of combustion and sublimation of 3,4,5-trimethoxyphenol were measured, respectively, by static bomb combustion calorimetry in oxygen atmosphere and by Calvet microcalorimetry. From these measurements, the standard molar enthalpy of formation in both the crystalline and gaseous phase, at T = 298.15 K, were derived: ?(643.4 ± 1.9) kJ · mol^?1 and ?(518.1 ± 3.6) kJ · mol^?1, respectively. Density functional theory calculations for this compound and respective phenoxyl radical and phenoxide anion were also performed using the B3LYP functional and extended basis sets, which allowed the theoretical estimation of the gaseous phase standard molar enthalpy of formation through the use of isodesmic reactions and the calculation of the homolytic and heterolytic O–H bond dissociation energies. There is good agreement between the calculated and experimental enthalpy of formation. Substituent effects on the homolytic and heterolytic O–H bond dissociation energies have been analysed.     

A theoretical analysis of the conformational space of tris(2-methylbenzimidazol-1-yl)methane

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.     

Experimental study on the thermochemistry of 1-(2H)-phthalazinone and phthalhydrazide

The standard (p^° = 0.1 MPa) molar enthalpies of combustion of 1-(2H)-phthalazinone and phthalhydrazide, both in the solid phase, were measured at T = 298.15 K by static bomb calorimetry. Further, the standard molar enthalpies of sublimation, at T = 298.15 K, of these two phthalazine derivatives were derived from the Knudsen effusion technique. The combustion calorimetry results together with those obtained from the Knudsen effusion technique, were used to derive the standard molar enthalpies of formation, at T = 298.15 K, in the gaseous phase for 1-(2H)-phthalazinone and phthalhydrazide, respectively as, (79.1 ± 1.8) kJ · mol^?1 and ?(107.4 ± 2.4) kJ · mol^?1.     

Solubility measurements of the uranyl oxide hydrate phases metaschoepite,compreignacite, Na–compreignacite,becquerelite, and clarkeite

The mobility of uranium under oxidizing conditions can only be modeled if the thermodynamic stabilities of the secondary uranyl minerals are known. Toward this end, we synthesized metaschoepite (UO₃(H₂O)₂), becquerelite (Ca(UO₂)₆O₄(OH)₆(H₂O)₈), compreignacite (K₂(UO₂)₆O₄(OH)₆(H₂O)₇), sodium compreignacite (Na₂(UO₂)₆O₄(OH)₆(H₂O)₇), and clarkeite (Na(UO₂)O(OH)) and performed solubility measurements from both undersaturation and supersaturation under controlled-pH conditions. The solubility measurements rigorously constrain the values of the solubility products for these synthetic phases, and consequently the standard-state Gibbs free energies of formation of the phases. The calculated lg solubility product values (lg K_sp), with associated 1σ uncertainties, for metaschoepite, becquerelite, compreignacite, sodium compreignacite, and clarkeite are (5.6 ?0.2/+0.1), (40.5 ?1.4/+0.2), (35.8 ?0.5/+0.3), (39.4 ?1.1/+0.7), and (9.4 ?0.9/+0.6), respectively. The standard-state Gibbs free energies of formation, with their 2σ uncertainties, for these same phases are (?1632.2 ± 7.4) kJ · mol^?1, (?10305.6 ± 26.5) kJ · mol^?1, (?10107.3 ± 21.8) kJ · mol^?1, (?10045.6 ±24.5) kJ · mol^?1, and (?1635.1 ± 23.4) kJ · mol^?1, respectively. Combining our data with previously measured standard-state enthalpies of formation for metaschoepite, becquerelite, sodium compreignacite, and clarkeite yields calculated standard-state entropies of formation, with associated 2σ uncertainties, of (?532.5 ± 8.1) J · mol^?1 · K^?1, (?3634.5 ± 29.7) J · mol^?1 · K^?1, ( ?2987.6 ± 28.5) J · mol^?1 · K^?1, and (?300.5 ± 23.9) J · mol^?1 · K^?1, respectively. The measurements and associated calculated thermodynamic properties from this study not only describe the stability and solubility at T = 298 K, but also can be used in predictions of uranium mobility through extrapolation of these properties to temperatures and pressures of geologic and environmental interest.     

Non-isothermal decomposition kinetics,thermal behavior and computational detonation properties on 4-amino-1,2,4-triazol-5-one (ATO)

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 E_a = 119.50 kJ mol⁻¹ and A = 10^9.03 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.     

Thermochemistry of two lead borates; Pb(BO2)2·H2O and PbB4O7·4H2O

Two pure hydrated lead borates, Pb(BO₂)₂·H₂O and PbB₄O₇·4H₂O, have been characterized by XRD, FT-IR, DTA-TG techniques and chemical analysis. The molar enthalpies of solution of Pb(BO₂)₂·H₂O and PbB₄O₇·4H₂O in 1 mol dm^?3 HNO₃(aq) were measured to be (?35.00 ± 0.18) kJ mol^?1 and (35.37 ± 0.14) kJ mol^?1, respectively. The molar enthalpy of solution of H₃BO₃(s) in 1 mol dm^?3 HNO₃(aq) was measured to be (21.19 ± 0.18) kJ mol^?1. The molar enthalpy of solution of PbO(s) in (HNO₃ + H₃BO₃)(aq) was measured to be ?(61.84 ± 0.10) kJ mol^?1. From these data and with incorporation of the enthalpies of formation of PbO(s), H₃BO₃(s) and H₂O(l), the standard molar enthalpies of formation of ?(1820.5 ± 1.8) kJ mol^?1 for Pb(BO₂)₂·H₂O and ?(4038.1 ± 3.4) kJ mol^?1 for PbB₄O₇·4H₂O were obtained on the basis of the appropriate thermochemical cycles.     

Kinetics,isotherm and thermodynamics for Cr(III) and Cr(VI) adsorption from aqueous solutions by crystalline hydrous titanium oxide

The synthetic crystalline hydrous titanium(IV) oxide (CHTO), an anatase variety and thermally stable up to 300 °C, has been used for adsorption of Cr(III) and Cr(VI) from the aqueous solutions, the optimum pH-values of which are 5.0 and 1.5, respectively. The kinetic data correspond very well to the pseudo-second order equation. The rates of adsorption are controlled by the film (boundary layer) diffusion, and increase with increasing temperature. The equilibrium data describe very well the Langmuir, Redlich–Peterson, and Toth isotherms. The monolayer adsorption capacities are high, and increased with increasing temperature. The evaluated ΔG^° (kJ · mol^?1) and ΔH^° (kJ · mol^?1) indicate the spontaneous and endothermic nature of the reactions. The adsorptions occur with increase in entropy (ΔS^° = positive), and the mean free energy (E_DR) values obtained by analysis of equilibrium data with Dubinin–Radushkevick equation indicate the ion-exchange mechanism for Cr(III) and Cr(VI)-adsorptions.     

Experimental and computational thermochemistry of 1,4-benzodioxan and its 2-R derivatives

The standard molar energies of combustion, at T = 298.15 K, of crystalline 1,4-benzodioxan-2-carboxylic acid and 1,4-benzodioxan-2-hydroxymethyl were measured by static bomb calorimetry in an oxygen atmosphere. The standard molar enthalpies of sublimation, at T = 298.15 K, were obtained by Calvet microcalorimetry. These values were used to derive the standard molar enthalpies of formation of the compounds in the gas phase at T = 298.15 K: 1,4-benzodioxan-2-carboxylic acid ?(547.7 ± 3.0) kJ · mol^?1 and 1,4-benzodioxan-2-hydroxymethyl ?(374.2 ± 2.3) kJ · mol^?1.In addition, density functional theory calculations using the B3LYP hybrid exchange–correlation energy functional with extended basis sets, 6-311G⁷ and cc-pVTZ, have been performed for the compounds studied. We have also tested two more accurate computational procedures involving multiple levels of electron structure theory in order to get reliable estimates of the thermochemical parameters of the compounds studied. The agreement between experiment and theory gives confidence to estimate the enthalpies of formation of other 2-R derivatives of 1,4-benzodioxan (R = –CH₂COOH, –OH, –COCH₃, –CHO, –CH₃, –CN, and –NO₂).