Kinetics of the CH3 + HCl/DCl → CH4/CH3D + Cl and CD3 + HCl/DCl → CD3H/CD4 + Cl reactions: An experimental H atom tunneling investigation

The kinetics of the radical reactions of CH₃ with HCl or DCl and CD₃ with HCl or DCl have been investigated in a temperature controlled tubular reactor coupled to a photoionization mass spectrometer. The CH₃ (or CD₃) radical, R, was produced homogeneously in the reactor by a pulsed 193 nm exciplex laser photolysis of CH₃COCH₃ (or CD₃COCD₃). The decay of CH₃/CD₃ was monitored as a function of HCl/DCl concentration under pseudo-first-order conditions to determine the rate constants as a function of temperature, typically from 188 to 500 K. The rate constants of the CH₃ and CD₃ reactions with HCl had strong non-Arrhenius behavior at low temperatures. The rate constants were fitted to a modified Arrhenius expression k = QA exp (−E_a/RT) (error limits stated are 1σ + Students t values, units in cm³ molecule⁻¹ s⁻¹): k(CH₃ + HCl) = [1.004 + 85.64 exp (−0.02438 × T/K)] × (3.3 ± 1.3) × 10⁻¹³ exp [−(4.8 ± 0.6) kJ mol⁻¹/RT] and k(CD₃ + HCl) = [1.002 + 73.31 exp (−0.02505 × T/K)] × (2.7 ± 1.2) × 10⁻¹³ exp [−(3.5 ± 0.5) kJ mol⁻¹/RT]. The radical reactions with DCl were studied separately over a wide ranges of temperatures and in these temperature ranges the rate constants determined were fitted to a conventional Arrhenius expression k = A exp (−E_a/RT) (error limits stated are 1σ + Students t values, units in cm³ molecule⁻¹ s⁻¹): k(CH₃ + DCl) = (2.4 ± 1.6) × 10⁻¹³ exp [−(7.8 ± 1.4) kJ mol⁻¹/RT] and k(CD₃ + DCl) = (1.2 ± 0.4) × 10⁻¹³ exp [−(5.2 ± 0.2) kJ mol⁻¹/RT] cm³ molecule⁻¹ s⁻¹.     

The investigation of the (p,ρ,T) and (ps,ρs,Ts) properties of {(1−x)CH3OH + xLiBr} for the application in absorption refrigeration machines and heat pumps

The (p,ρ,T) and (p_s,ρ_s,T_s) properties of {(1−x)CH₃OH + xLiBr} over a wide range of state parameters are reported for the first time. The experiments were carried out in a constant volume piezometer over a temperature range from 298.15 K to 398.15 K, at 0.08421, 0.13617, 0.19692, 0.23133 and 0.26891 mole fractions and from atmospheric pressure up to 60 MPa. The experimental uncertainties are ΔT=±3 mK for temperature, Δp=±5·10⁻² MPa for high pressure and Δp=±5·10⁻⁴ MPa for atmospheric pressure, Δρ=±3·10⁻² kg · m⁻³ for density. An equation of state was derived for correlation of the experimental data of the solutions.     

DFT and ab initio theoretical study for the CF3S + CO reaction

The potential energy surface for the reaction of CF₃S with CO is calculated at the G4//B3LYP/6-311++G(d,p) level of theory. The results show that F-abstraction and addition-elimination mechanisms are involved, and the latter one is dominant thermodynamically and kinetically. The dominant channel is the reactant addition to form CF₃SCO, and then decomposes to CF₃ + OCS. While the direct F-abstraction channel and CF₃SCO isomerization channel are not significant for the title reaction due to higher barriers involved. The comparisons among four reactions of CX₃Y + CO (X = H, F; and Y = O, S) are made to imply the similar and different properties and reactivities of the same family elements and the F- and S-substituted derivatives.     

Solid–liquid equilibrium and hydrogen solubility of trans-decahydronaphthalene + naphthalene and cis-decahydronaphthalene + naphthalene for a new hydrogen storage medium in fuel cell system

Solid–liquid equilibrium was measured for benzene + cyclohexane, trans-decahydronaphthalene + naphthalene and cis-decahydronaphthalene + naphthalene under the atmospheric pressure in the temperature range from 226.69 to 353.14 K. The apparatus was specially designed in this study, and it was based on a cooling method. The phase diagram with the complete immiscible solids was observed for the three systems, and the eutectic point was found at x₂ = 0.2709 and T_eu = 232.11 K for benzene + cyclohexane, x₂ = 0.9816 and T_eu = 241.98 K for trans-decahydronaphthalene + naphthalene, and x₃ = 0.9822 and T_eu = 225.74 K for cis-decahydronaphthalene + naphthalene, respectively. Hydrogen solubility was also measured for the two pure substances, trans-decahydronaphthalene and cis-decahydronaphthalene, and the three mixtures, trans-decahydronaphthalene + cis-decahydronaphthalene, trans-decahydronaphthalene + naphthalene, and cis-decahydronaphthalene + naphthalene, in the pressure range from 1.702 to 4.473 MPa at 303.15 K. Considering the solid–liquid equilibrium data, mole ratio of trans-decahydronaphthalene:cis-decahydronaphthalene was set to 50:50, and those of trans-decahydronaphthalene + naphthalene, and cis-decahydronaphthalene + naphthalene to 85:15. The hydrogen solubility increased linearly with the pressure following the Henry's law for all systems. The experimental solubility data were correlated or predicted with the Peng–Robinson equation of state [D.Y. Peng, D.B. Robinson, Ind. Eng. Chem. Fundam. 15 (1976) 59–64; R. Stryjek, J.H. Vera, Can. J. Chem. Eng. 64 (1986) 323–333].     

Vapour pressure and excess Gibbs free energy of the ternary system {x1CH3F + x2HCl + x3N2O} at temperature of 182.33 K

The equilibrium pressure of ternary mixtures of {x₁CH₃F + x₂HCl + x₃N₂O} covering the entire composition range has been measured at temperature of 182.33 K by the static method. The system exhibits a minimum pressure for the binary {x₁CH₃F + x₂HCl}. The molar excess Gibbs free energy has been calculated from the experimental equilibrium pressure. For the equimolar mixture . The (p, x, y) surface for the ternary system and the corresponding curves for the three constituent binary mixtures obtained from the Peng-Robinson equation of state are in agreement with the experimental data.     

Iodomethane oxidative addition and CO migratory insertion in monocarbonylphosphine complexes of the type [Rh((C6H5)COCHCO((CH2)nCH3))(CO)(PPh3)]: Steric and electronic effects

The chemical kinetics, studied by UV/Vis, IR and NMR, of the oxidative addition of iodomethane to [Rh((C₆H₅)COCHCOR)(CO)(PPh₃)], with R = (CH₂)_nCH₃, n = 1-3, consists of three consecutive reaction steps that involves isomers of two distinctly different classes of Rh^III-alkyl and two distinctly different classes of Rh^III-acyl species. Kinetic studies on the first oxidative addition step of [Rh((C₆H₅)COCHCOR)(CO)(PPh₃)] + CH₃I to form [Rh((C₆H₅)COCHCOR)(CH₃)(CO)(PPh₃)(I)] revealed a second order oxidative addition rate constant approximately 500-600 times faster than that observed for the Monsanto catalyst [Rh(CO)₂I₂]⁻. The reaction rate of the first oxidative addition step in chloroform was not influenced by the increasing alkyl chain length of the R group on the β-diketonato ligand: k₁ = 0.0333 ([Rh((C₆H₅)COCHCO(CH₂CH₃))(CO)(PPh₃)]), 0.0437 ([Rh((C₆H₅)COCHCO(CH₂CH₂CH₃))(CO)(PPh₃)]) and 0.0354 dm³ mol⁻¹ s⁻¹ ([Rh((C₆H₅)COCHCO(CH₂CH₂CH₂CH₃))(CO)(PPh₃)]). The pK_a^′ and keto-enol equilibrium constant, K_c, of the β-diketones (C₆H₅)COCH₂COR, along with apparent group electronegativities, χ_R of the R group of the β-diketones (C₆H₅)COCH₂COR, give a measurement of the electron donating character of the coordinating β-diketonato ligand: (R, pK_a^′, K_c, χ_R) = (CH₃, 8.70, 12.1, 2.34), (CH₂CH₃, 9.33, 8.2, 2.31), (CH₂CH₂CH₃, 9.23, 11.5, 2.41) and (CH₂CH₂CH₂CH₃, 9.33, 11.6, 2.22).     

New isothermal vapor–liquid equilibria for the CO2 + n-nonane,and CO2 + n-undecane systems

Experimental vapor–liquid equilibria (VLE) for the CO₂ + n-nonane and CO₂ + n-undecane systems were obtained by using a 100-cm³ high-pressure titanium cell up to 20 MPa at four temperatures (315, 344, 373, and 418 K). The apparatus is based on the static-analytic method; which allows fast determination of the coexistence curve. For the CO₂ + n-nonane system, good agreement was found between the experimental data and those reported in literature. No literature data were available for the CO₂ + n-undecane system at high temperature and pressure. Experimental data were correlated with the Peng–Robinson equation of state using the classical and the Wong–Sandler mixing rules.     

Infrared and Raman studies of the anion ordering transitions in paramagnetic organometallic radical cation salts [Cp2Mo(dmit)]X (X = PF6, SbF6)

Temperature dependence of infrared and Raman spectra of the two isostructural salts [Cp₂Mo(dmit)]PF₆ and [Cp₂Mo(dmit)]SbF₆ is studied. At room temperature the physical properties of both compounds are very similar but at lower temperatures they undergo phase transitions associated with anion ordering, which are surprisingly different. The phase transitions in [Cp₂Mo(dmit)]PF₆ salt at T₁ = 120 K and T₂ = 89 K have no important influence on infrared and Raman spectra, while the phase transition in [Cp₂Mo(dmit)]SbF₆ salt at T₁ = 175 K causes a splitting of Raman bands assigned to the CC stretching at about 1334 cm⁻¹ and the in-plane Mo(dmit) ring deformation at about 353 cm⁻¹, and also an infrared band at about 939 cm⁻¹ related to the C-S stretching. The splitting of vibrational bands demonstrates a clear distortion of [Cp₂Mo(dmit)]⁺ cations in the [Cp₂Mo(dmit)]SbF₆ salt. This molecular distortion is related to a lattice distortion providing thus a good argument for applicability of the compressible model of the anion ordering transition.     

Complex formation of crown ethers with cations in the (water + organic solvent) mixtures: Part IX. Thermodynamics of interactions of Na ion with benzo-15-crown-5 ether in {(1 − x)DMA + xH2O} at T = 298.15 K

The thermodynamic functions of complex formation of benzo-15-crown-5 ether with sodium cation in {(1 − x)DMA + xH₂O} at T = 298.15 K have been calculated. The equilibrium constants of complex formation of benzo-15-crown-5 ether with sodium cation have been determined by conductivity measurements. The enthalpic effect of complex formation has been measured by calorimetric method at T = 298.15 K. The complexes are enthalpy stabilized and entropy destabilized. A simple model has been proposed to describe the relationship between the thermodynamic functions of complex formation of crown ethers with sodium cation and the structural and energetic properties of the mixed water-organic solvent. The linear enthalpy-entropy relationship for complex formation is also presented. The solvation enthalpy of the complex in {(1 − x)DMA + xH₂O} is discussed.     

Thermodynamics of 2D polymerized tetragonal phase of fullerene C60 in the range from T→0 to 650 K at standard pressure

By dynamic calorimetry the temperature dependence of heat capacity for two-dimensional (2D) polymerized tetragonal phase of C₆₀ has been determined over the 300-650 K range at standard pressure mainly with an uncertainty ±1.5%. In the range 490-550 K, an irreversible endothermic transition of the phase, caused by the depolymerization of the polymer, has been found and characterized. Based on the experimental data obtained and literature information, the thermodynamic functions of 2D polymerized tetragonal phase of C₆₀, namely, the heat capacity C°_p(T), enthalpy H°(T)−H°(0), entropy S°(T), and Gibbs function G°(T)−H°(0), have been calculated over the range from T→0 to 490 K. From 150 to 330 K in an adiabatic vacuum calorimeter and between 330 and 650 K in a dynamic calorimeter the thermodynamic properties of the depolymerization products have been examined and compared with the corresponding data for the monomeric phase C₆₀.     

Heat capacity, enthalpy and entropy of bismuth niobate and bismuth tantalate

The heat capacity and the heat content of bismuth niobate BiNbO₄ and bismuth tantalate BiTaO₄ were measured by the relaxation method and Calvet-type heat flux calorimetry. The temperature dependencies of the heat capacities in the form C_pm=128.628+0.03340 T−1991055/T²+136273131/T³ (J K^-1 mol^-1) and 133.594+0.02539 T−2734386/T²+235597393/T³ (J K^-1 mol^-1) were derived for BiNbO₄ and BiTaO₄, respectively, by the least-squares method from the experimental data. Furthermore, the standard molar entropies at 298.15 K S_m(BiNbO₄)=147.86 J K^-1 mol^-1 and S_m(BiTaO₄)=149.11 J K^-1 mol^-1 were assessed from the low temperature heat capacity measurements. To complete a set of thermodynamic data of these mixed oxides an attempt was made to estimate the values of the heat of formation from the constituent binary oxides.     

Thermophysical properties of SrHfO3 and SrRuO3

Polycrystalline samples of strontium series perovskite type oxides, SrHfO₃ and SrRuO₃ were prepared and the thermophysical properties were measured. The average linear thermal expansion coefficients are 1.13×10⁻⁵ K⁻¹ for SrHfO₃ and 1.03×10⁻⁵ K⁻¹ for SrRuO₃ in the temperature range between 423 and 1073 K. The melting temperatures T_m of SrHfO₃ and SrRuO₃ are 3200 and 2575 K, respectively. The longitudinal and shear sound velocities were measured by an ultrasonic pulse-echo method at room temperature in air, which enables to evaluate the elastic moduli and Debye temperature. The heat capacity was measured by using a differential scanning calorimeter, DSC in high-purity argon atmosphere. The thermal diffusivity was measured by a laser flash method in vacuum. The thermal conductivities of SrHfO₃ and SrRuO₃ at room temperature are 5.20 and 5.97 W m⁻¹ K⁻¹, respectively.     

Modeling of the three-phase equilibrium in systems of the type water + nonionic surfactant + alkane

Liquid–liquid equilibria of systems water (A) + C_iE_j surfactant (B) + n-alkane (C) have been modeled by a mass-action law model previously developed and so far successfully applied to a series of binary water + C_iE_j systems and to the ternary system water + C₄E₁ + n-dodecane. These calculations provide the basis for the presented modeling. The aqueous systems give information about the association constants and the χ_AB-parameter of the Flory–Huggins theory and the ternary C₄E₁-system provides universal temperature functions for the χ_AC- and the χ_BC-parameter. The three-phase equilibrium for seven ternary C_iE_j systems (i = 6–12, j = 3–6) has been calculated by fitting one additional parameter for each of both temperature functions to the characteristic “fish-tail” point. The agreement with the experimental data is reasonably well. For systems with very small three-phase areas the results can considerably be improved by individual temperature functions that incorporate the experimental temperature maximum of the “fish” into the parameter fit. Based on the parameters of the system water + C₈E₄ + n-C₈H₁₈ the “fish-shaped” phase diagram of the system water + C₈E₄ + n-C₁₄H₃₀ was predicted reasonably well.     

Theoretical study of the thermochemistry and the kinetics of the SFxCl (x = 0-5) series

A systematic thermodynamic and kinetic study of the entire SF_xCl (x = 0-5) series has been carried out. High-level quantum chemical composite methods have been employed to derive enthalpy of formation values from calculated atomization and isodesmic energies. The resulting values for the SCl, SFCl, SF₂Cl(C₁), SF₃Cl(C_s), SF₄Cl(C_s) and SF₅Cl molecules are 28.0, −36.0, −64.2, −134.3, −158.2 and −237.1 kcal mol⁻¹. A comparison with previous experimental and theoretical values is presented. Statistical adiabatic channel model/classical trajectory, SACM/CT, calculations of selected complex-forming and recombination reactions of F and Cl atoms with radicals of the series have been performed between 200 and 500 K. The reported rate coefficients span over the normal range of about 6 × 10⁻¹² and 5 × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹ expected for this type of barrierless reactions.     

Heat capacity and thermodynamic functions of LuPO4 in the range 0-320 K

The heat capacity of LuPO₄ was measured in the temperature range 6.51-318.03 K. Smoothed experimental values of the heat capacity were used to calculate the entropy, enthalpy and Gibbs free energy from 0 to 320 K. Under standard conditions these thermodynamic values are: (298.15 K) = 100.0 ± 0.1 J K⁻¹ mol⁻¹, S⁰(298.15 K) = 99.74 ± 0.32 J K⁻¹ mol⁻¹, H⁰(298.15 K) − H⁰(0) = 16.43 ± 0.02 kJ mol⁻¹, −[G⁰(298.15 K) − H⁰(0)]/T = 44.62 ± 0.33 J K⁻¹ mol⁻¹. The standard Gibbs free energy of formation of LuPO₄ from elements Δ_fG⁰(298.15 K) = −1835.4 ± 4.2 kJ mol⁻¹ was calculated based on obtained and literature data.     

Thermodynamics of complexation of aqueous 18-crown-6 with potassium ion: apparent molar volumes and apparent molar heat capacities of aqueous 18-crown-6 and of the (18-crown-6 + potassium chloride) complex at temperatures (278.15 to 393.15) K, at molalities (0.02 to 0.3) mol · kg, and at the pressure 0.35 MPa

We have measured the densities at temperatures T = (278.15 to 363.15) K and heat capacities at T = (278.15 to 393.15) K of aqueous solutions of 18-crown-6 and of (18-crown-6 + KCl) at molalities m = (0.02 to 0.3) mol · kg⁻¹ and at the pressure 0.35 MPa. We have calculated apparent molar volumes V_? and apparent molar heat capacities C_p,? for 18-crown-6(aq), and we have applied Young’s Rule and have accounted for chemical speciation and relaxation effects to resolve V_? and C_p,? for the (18-crown-6: K⁺,Cl⁻)(aq) complex in the mixture. We have also calculated estimates of the change in volume Δ_rV_m, the change in heat capacity Δ_rC_p,m, the change in enthalpy Δ_rH_m, and the equilibrium quotient log Q for formation of the complex at T = (278.15 to 393.15) K and m = (0 to 0.3) mol · kg⁻¹.     

Physical properties of 3-methyl-N-butylpyridinium tricyanomethanide and ternary LLE data with an aromatic and an aliphatic hydrocarbon at T = (303.2 and 328.2) K and p = 0.1 MPa

Several physical properties were determined for the ionic liquid 3-methyl-N-butylpyridinium tricyanomethanide ([3-mebupy]C(CN)₃): liquid density, viscosity, surface tension, thermal stability and heat capacity in the temperature range from (283.2 to 363.2) K and at 0.1 MPa. The density and the surface tension could well be correlated with linear equations and the viscosity with a Vogel-Fulcher-Tamman equation. The IL is stable up to a temperature of 420 K.Ternary data for the systems {benzene + n-hexane, toluene + n-heptane, and p-xylene + n-octane + [3-mebupy]C(CN)₃} were determined at T = (303.2 and 328.2) K and p = 0.1 MPa. All experimental data were well correlated with the NRTL model. The experimental and calculated aromatic/aliphatic selectivities are in good agreement with each other.     

High-pressure phase behaviour of binary (CO2 + nicotine) and ternary (CO2 + nicotine + solanesol) mixtures

This work paper presents vapour–liquid equilibrium (VLE) data for binary (CO₂ + nicotine) and ternary (CO₂ + nicotine + solanesol) mixtures, at 313.2 K and 6, 8 and 15 MPa. The (CO₂ + nicotine) system exhibits three phases (L₁L₂V) in equilibrium at 8.37 MPa. It is estimated that this system most likely follows the type-III phase behaviour. In the ternary system, the presence of solanesol in the vapour phase was detected only at the pressure of 15 MPa. At this pressure, partition coefficients and separation factors for solanesol/nicotine were calculated for different initial nicotine/solanesol compositions and a strong influence of composition was found. The results were modelled using the Peng–Robinson equation of state (PR EOS) coupled with the Mathias–Klotz–Prausnitz (MKP) mixing rule (PR–MKP model). Good correlations of the binary data, particularly in the case of the (CO₂ + nicotine) mixture, were obtained. However, the model could not correlate the ternary data.     

Activity coefficients of NaCl in the NaCl + NaBF4 + H2O ternary system at 298.15 K

The activity coefficients of sodium chloride in the NaCl + NaBF₄ + H₂O ternary system were experimentally determined at 298.15 K, at ionic strengths of 0.3. 0.5, 1, 2 and 3 mol kg⁻¹ from emf from the bi-ISE cell without liquid junction:

ISE-Na|NaCl(m_A), NaBF₄(m_B)|ISE-Cl

Ion-beam irradiation of lanthanum compounds in the systems La2O3-Al2O3 and La2O3-TiO2

Thin crystals of La₂O₃, LaAlO₃, La_2/3TiO₃, La₂TiO₅, and La₂Ti₂O₇ have been irradiated in situ using 1 MeV Kr²⁺ ions at the Intermediate Voltage Electron Microscope-Tandem User Facility (IVEM-Tandem), Argonne National Laboratory (ANL). We observed that La₂O₃ remained crystalline to a fluence greater than 3.1×10¹⁶ ions cm⁻² at a temperature of 50 K. The four binary oxide compounds in the two systems were observed through the crystalline-amorphous transition as a function of ion fluence and temperature. Results from the ion irradiations give critical temperatures for amorphisation (T_c) of 647 K for LaAlO₃, 840 K for La₂Ti₂O₇, 865 K for La_2/3TiO₃, and 1027 K for La₂TiO₅. The T_c values observed in this study, together with previous data for Al₂O₃ and TiO₂, are discussed with reference to the melting points for the La₂O₃-Al₂O₃ and La₂O₃-TiO₂ systems and the different local environments within the four crystal structures. Results suggest that there is an observable inverse correlation between T_c and melting temperature (T_m) in the two systems. More complex relationships exist between T_c and crystal structure, with the stoichiometric perovskite LaAlO₃ being the most resistant to amorphisation.