The excess molar volumes of (an alkanol + a branched chain ether) at the temperature 298.15 K and the application of the ERAS model

The excess molar volumes V_m^E {x(CH₃OH or CH₃CH₂OH or CH₃(CH₂)₂OH or CH₃CH(OH)CH₃ + (1 - x){CH₃(CH₂)₂}₂O or CH₃C(CH₃)₂OCH₃ or CH₃CH₂C(CH₃)₂OCH₃} have been calculated from measured values of density over the whole composition range at the temperature 298.15 K in order to investigate OH … O specific interactions. The results are explained in terms of the strong self-association of the alkanols, the specific interaction between the alkanol, and the ether molecules and packing effects upon mixing. The experimental V_m^h results presented here, together with the previously reported data for the molar excess enthalpy H_m^E, has been used to test the Extended Real Associated Solution (ERAS) model.     

Thermoynamic properties (Hm, CP,m, Vm, κT) of binary mixtures {x1,3-Dioxane + (1−x)Cyclohexane} at 298.15 K

Molar excess enthalpies H_m^E, isobaric heat capacities C_P,m^E, volumes V_m^E and isothermal compressibilities κT^E for the 1,3-dioxane(3DX) + cyclohexane mixture were measured at 298.15 K, in order to compare to those of the 1,4-dioxane(4DX) + cyclohexane mixture. H_m^E is endothermic and the maximum value about 1.5 kJ mol⁻¹ at x ≈ 0.45, and lower than that of the 4DX mixture by about 80 J mol⁻¹. V_m^E is positive over the whole concentration and the maximum value is about 0.85 cm³ mol⁻¹ at x ≈ 0.45, and lower than that of the 4DX mixture. The above results suggest the energetic unstabilization, resulting in the volume expansion in the mixture. C_P,m^E shows the characteristic W-shaped concentration dependence, which has maximum at x ≈ 0.45 and two minima at x ≈ 0.1 and 0.9. The maximum C_P,m^E value for 3DX mixture shifts toward the positive side, compared to that of 4DX mixture. κT^E were estimated from speeds of sound, densities, thermal expansion coefficients and isobaric heat capacities of the pure component liquids and the mixtures. The κT^E result shows the positive concentration dependence over the whole composition range. The 3DX mixture has the similar thermodynamic properties to the 4DX mixture, despite that 4DX is the nonpolar solvent and 3DX is the dipolar liquid. this means that there exists the local dipolar interaction between 4DX molecules, and the prevalence of “microheterogeneity” in the both mixtures.     

Thermodynamics of (1,4-difluorobenzene + an n-alkane) and of (hexafluorobenzene + an n-alkane)

Excess molar enthalpies H^E and excess molar volumes V^E have been measured, as a function of mole fraction x₁, at 298.15 K and atmospheric pressure for the five liquid mixtures (x₁1,4-C₆H₄F₂ + x₂n-C_lH_2l+2), l = 7, 8, 10, 12 and 16. In addition, H^E and excess molar heat capacities C_P^E at constant pressure have been determined for the two liquid mixtures (x₁C₆F₆ + x₂n-C_lH_2l+2), l = 7 and 14, at the same temperature and pressure. The instruments used were flow microcalorimeters of the Picker design (the H^E version was equipped with separators) and a vibrating-tube densimeter, respectively.

The excess enthalpies of the five difluorobenzene mixtures are all positive and quite large; they increase with increasing chain length l of the n-alkane from H^E(x₁ = 0.5)/(J mol⁻¹) = 1050 for l = 7 to 1359 for l = 16. The corresponding excess volumes V^E are all positive and also increase with increasing l: V^E(x₁ = 0.5)/(cm³ mol⁻¹) = 0.650 for l = 7 and 1.080 for l = 16. Interestingly, the excess enthalphies of the corresponding mixtures with hexafluorobenzene are only about 5% larger, whereas the excess volumes of (x₁C₆F₆ + x₂n-C_lH_2l+2) are roughly twice as large as those of their counterparts in the series containing 1,4-C₆H₄F₂. Specifically, at 298.15 K H^E(x₁ = 0.5)/(J mol⁻¹) = 1119 for (x₁C₆F₆ + x₂n-C₇H₁₆) and 1324 for (x₁C₆F₆ + x₂n-C₁₄H₃₀), and for the same mixtures V^E(x₁ = 0.5)/(cm³ mol⁻¹) = 1.882 and 2.093, respectively. The excess heat capacities for both systems are negative and of about the same magnitude as the excess heat capacities of mixtures of fluorobenzene with the same n-alkanes (Roux et al., 1984): C_P^E(x₁ = 0.5)/(J K⁻¹ mol⁻¹) = −1.18 for (x₁C₆F₆ + x₂n-C₇H₁₆), and −2.25 for (x₁C₆F₆ + x₂n-C₁₄H₃₀). The curve C_P^E vs. (x₁ for x₁C₆F₆ + x₂n-C₁₄H₃₀) shows a sort of “hump” for x₁ 0.5, which is presumed to indicate emerging W-shape composition dependence at lower temperatures.     

Effect of oxyethylene groups on the behaviour of thermodynamic properties of pyrrolidin-2-one and poly(ethylene glycols)

Dilatometric measurements of excess volume V^E and ultrasonic speed u have been carried out for mixtures of mono-, di-, tri- and tetra(ethylene glycol)s in pyrrolidin-2-one (PY) over the whole mole fraction range at 303.15 K. In the mixture of PY and monoethylene glycol, the V^E is positive except for slight negative variation at the high mole fraction of PY. The other three mixtures PY + di-, + tri- and + tetra(ethylene glycol)s show negative V^E over the entire composition range in the order di-u with increase in the mole fraction of PY in the case of monoethylene glycol while for other three systems u rises. From these measurements, partial molar quantities V_i^E and K_S,i^E have been calculated and analysed. Estimates of isentropic molar quantity K_S equal to −(∂V/∂p)_S and its excess counterpart K_S^E have also been computed. The K_S^E is positive for mono-, and negative for all the other mixtures over the whole composition range.     

Thermodynamics of mixtures with strongly negative deviations from Raoult’s law: Part 5. Excess molar volumes at 298.15 K for 1-alkanols+dipropylamine systems: characterization in terms of the ERAS model

Excess molar volumes, V_m^E, at 298.15 K and atmospheric pressure over the entire composition range for binary mixtures of methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol, 1-hexanol, 1-heptanol and 1-octanol with dipropylamine are reported from densities measured with a vibrating-tube densimeter. All the excess volumes are large and negative over the whole mole fraction range, indicating strong interactions between unlike molecules, which are more important for the system involving methanol, characterized by the most negative V_m^E. For the remainder mixtures, V_m^E at equimolar composition, is approximately constant. The V_m^E curves are nearly symmetrical.

V_m^E and excess molar enthalpies, H_m^E, of the mixtures studied are consistently described by the ERAS model. The ERAS parameters confirm that the strongest interactions between unlike molecules are encountered in the methanol+dipropylamine system.     

Some further considerations on deriving matrix elements of non-periodic potentials in the basis of the non-degenerate harmonic oscillator wavefunctions

Using the properties of the generating function of the Hermite polynomials, we have calculated the matrix elements for the Gaussian-type potential V_G(x)=A exp{−B(x−C)²} and for the Morse-type potential V_M(x)=D_e[1−exp(−ax)]² in the basis of the non-degenerate harmonic oscillator wavefunctions. The final forms of these matrix elements are very simple to use and hence suitable for the numerical resolution of the Schrödinger equation for multiple-well potentials or anharmonic oscillators.     

Pressure and temperature dependencies of excess molar enthalpies of two-component Lennard–Jones fluid mixtures in the supercritical region

Monte Carlo (MC) simulations have been carried out for mixtures of Lennard–Jones (LJ) fluids near or in the supercritical region. Excess molar enthalpy at equimolar concentration, H_p,x=0.5^E, has been obtained for four kinds of model mixtures each having different combining rule for unlike interactions. The pressure and temperature dependencies of H_p,x=0.5^E are investigated. The unique pressure and temperature dependencies of H_p,x=0.5^E for real systems such as (ethane+ethene) in the supercritical condition have been reproduced by the present simple model systems. Excess molar internal energies at constant volumes, U_V,x=0.5^E, are also evaluated. They are compared with H_p,x=0.5^E to investigate the volumetric contributions to H_p,x=0.5^E or excess molar internal energies at constant pressure, U_V,x=0.5^E. Calculated U_V,x=0.5^E for the present model systems are quite simple compared to the excess molar internal energy at constant pressure, U_V,x=0.5^E. They are very small in magnitude and show linear dependencies on the density of mixtures.     

Metallorganische verbindungen der lanthanoide LVIII. Zur struktur des dicyclopentadienyl-bis(trimethylsilyl)lutetat-anions

(C₅H₅)₂Lu(μ-Cl₂)Na(dme)₂ reacts with LiSi(CH₃)₃ in dimethoxyethane with formation of [Li(dme)₃][(C₅H₅)₂Lu(Si(CH₃)₃)₂]. The crystal structure study shows the compound to consist of discrete ions [Li(dme)₃]⁺ and [(C₅H₅)₂Lu(Si(CH₃)₃)₂]⁻. The compound crystallizes in the space group P2/n with a 14.497(5) b 9.041(2), c 14.672(6) Å, β 103.85(3)° and V 1867(2) ų. The crystal and molecular structure was refined to R = 0.0473 for 2491 observed reflections with F_o 3σ(F_o).     

Structure and redox properties of CexPr1−xO2−δ mixed oxides and their catalytic activities for CO, CH3OH and CH4 combustion

A series of Ce_xPr_1−xO_2−δ mixed oxides were synthesized by a sol–gel method and characterized by Raman, XRD and TPR techniques. The oxidation activity for CO, CH₃OH and CH₄ on these mixed oxides was investigated. When the value x was changed from 1.0 to 0.8, only a cubic phase CeO₂ was observed. The samples were greatly crystallized in the range of the value x from 0.99 to 0.80, which is due to the formation of solid solutions caused by the complete insertion of Pr into the CeO₂ crystal lattices. Raman bands at 465 and 1150 cm⁻¹ in Ce_xPr_1−xO_2−δ samples are attributed to the Raman active F_2g mode of CeO₂. The broad band at around 570 cm⁻¹ in the region of 0.3 ≤ x ≤ 0.99 can be linked to oxygen vacancies. The new band at 195 cm⁻¹ may be ascribed to the asymmetric vibration caused by the formation of oxygen vacancies. The TPR profile of Pr₆O₁₁ shows two reduction peaks and the reduction process is followed: . The reduction temperature of Ce_xPr_1−xO_2−δ mixed oxides is lower than those of Pr₆O₁₁ or CeO₂. TPR results indicate that Ce_xPr_1−xO_2−δ mixed oxides have higher redox properties because of the formation of Ce_xPr_1−xO_2−δ solid solutions. The presence of the oxygen vacancies favors CO and CH₃OH oxidation, while the activity of CH₄ oxidation is mostly related to reduction temperatures and redox properties.     

On the vibrational spectra and conformational stability of 1,1-dimethylhydrazine from temperature dependent FT-IR spectra of krypton solutions and ab initio calculations

Variable temperature (−105 to −150 °C) studies of the infrared spectra (3500–400 cm⁻¹) of 1,1-dimethylhydrazine, (CH₃)₂NNH₂, in liquid krypton have been carried out. No convincing spectral evidence could be found for the trans conformer which is expected to be at least 600 cm⁻¹ less stable than the gauche form. The structural parameters, dipole moments, conformational stability, vibrational frequencies, and infrared and Raman intensities have been predicted from MP2/6-31G(d) ab initio calculations. The predicted infrared and Raman spectra are compared to the experimental ones. The adjusted r₀ parameters from MP2/6-311+G(d,p) calculations are compared to those reported from an electron diffraction study. The energy differences between the gauche and trans conformers have been obtained from MP2 ab initio calculations as well as from density functional theory by the B3LYP method calculations from a variety of basis sets. All of these calculations indicate an energy difference of 650–900 cm⁻¹ with the B3LYP calculations predicted the larger values. The potential function governing the conformational interchange has been predicting from both types of calculations and comparisons have been made. The barrier to internal rotation by the independent rotor model of the inner methyl group is predicted to have a value of 1812 cm⁻¹ and that of the outer one of 1662 cm⁻¹ from ab initio MP2/6-31G(d) calculations. These values agree well with the experimentally determined values of 1852±16 and 1558±12 cm⁻¹, respectively, from a fit of the torsional transitions with the coupled rotor model. For the coupled rotor model the predicted V′₃₃ (sin 3τ₀ sin 3τ₁ term) value which ranged from 190 to 232 cm⁻¹ is in reasonable agreement with the experimental value of 268±3 cm⁻¹ but the predicted V₃₃ (cos 3τ₀ cos 3τ₁ term) value of −73 to −139 cm⁻¹ is 25% smaller and of the opposite sign of the experimental value of 333±22 cm⁻¹. These theoretical and spectroscopy results are compared to similar quantities of some corresponding molecules.     

Synthesis of ferrocenyl-1,2-diketones and related compounds: Crystal and molecular structures of 1,2-diferrocenylethanedione and 1-ferrocenyl-2-(4-biphenylyl) ethanedione

Ferrocenyl-1,2-diketones FcCOCOR, 3, [Fc = (C₅H₅)Fe(C₅H₄)] can be prepared by oxidation of acylferrocenes FcCOCH₂R or, more efficiently, by oxidation of the isomeric ketones FcCH₂COR, 2. The ketones 2 are in turn readily synthesized from the salt (FcCH₂PPh₃)⁺I⁻ via the acylated salts [FcCH(COR)PPh₃]⁺I⁻. The haloacylferocenes FcCOCCl_x H_3−x (x = 1, 2, 3, of which the x = 2 example is synthetically equivalent to a diketone) are synthesized by Friedel—Crafts acylation of ferrocene using CCl_xH_3−xCOCl/AlCl₃, but the reaction proceeds via two parallel pathways, one giving the normal acyl derivatives FcCOCCl_xH_3−x and the other giving the reduced products FcCOCCl_x−1H_4−x. Two diketones FcCOCOFc 3b and FcCOCOC₆H₄Ph 3c have been structurally characterised by single-crystal X-ray diffraction.     

Highly stereoselective reduction of methyl ketone complexes of the chiral Lewis acid [(η-C5H5)Re(NO)(PPh3)] by K(s-C4H9)3BH; synthesis of optically active secondary alcohols and derivatives

Reaction of optically active ketone complexes (+)-(R)-[(η⁵-C₅H₅)Re(NO)-(PPh₃)(η¹-O=C(R)(CH₃)]⁺ BF₄⁻ (R = CH₂CH₃, CH(CH₃)₂m C(CH₃)₃, C₆H₅) with K(s-C₄H₉)₃BH gives alkoxide complexes (+)-(RS)-(η⁵-C₅H₅)Re(NO)(PPh₃)-(OCH(R)CH₃) (73–90%) in 80–98% de. The alkoxide ligand is then converted to Mosher esters (93–99%) of 79–98% de.     

Anionic derivatives of pentafluoro-λ-sulfanyl (fluorosulfonyl) acetic acid esters

New ester salts [R₃NH]⁺[F₅SC(SO₂F)C(O)OR′]⁻ where RH, CH₃CH₂ and R′CH₃,(CH₃)₂CH have been prepared from corresponding esters and amines. The sodiumsalt Na[F₅SC(SO₂F)C(O)OCH(CH₃)₂] was used to prepare the following -substitutedderivatives: SF₅CX(SO₂F)C(O)OCH(CH₃)₂, XBr, Cl. The crystal structure of[(C₂H₅)₃NH]⁺[F₅SC(SO₂F)C(O)OCH₃]⁻ was determined and is monoclinic: P2₁/n;a=8.758(2) Å, b=9.645(2) Å and c=19.167(4) Å; β=97.92(3)°; V=1603.6 ų; Z=4.     

Rates of the reactions CN + H2CO and NCO + H2CO in the temperature range 294–769 K

The rate coefficients of the reactions: (1) CN + H₂CO → products and (2) NCO + H₂CO → products in the temperature range 294–769 K have been determined by means of the laser photolysis-laser induced fluorescence technique. Our measurements show that reaction (1) is rapid: k₁(294 K) = (1.64 ± 0.25) x 10⁻¹¹ cm³ molecule⁻¹ s⁻¹; the Arrhenius relation was determined as k₁ = (6.7 ± 1.0) x 10⁻¹¹ exp[(−412 ± 20)/T] cm³ molecule⁻¹ s⁻¹. Reaction (2) is approximately a tenth as rapid as reaction (1) and the temperature dependence of k₂ does not conform to the Arrhenius form: k₂ = 4.62 x 10⁻¹⁷T^1.71 exp(198/T) cm³ molecule⁻¹ s⁻¹. Our values are in reasonable agreement with the only reported measurement of k₁; the rate coefficients for reaction (2) have not been previously reported.     

New temperature effect on tunneling reaction in hydrogen, alkane, and ethanol in the solid phase

Rate constants for the tunneling reaction (HD + D → h + D₂) in solid HD increase steeply with increasing temperature above 5 K, while they are almost constant below 4.2 K. The apparent activation energy for the tunneling reaction above 5 K is 95 K, which is consistent with the energy (91–112 K) for vacancy formation in solid hydrogen. The results above 5 K were explained by the model that the tunneling reaction was accelerated by a local motion of hydrogen molecules and hydrogen atoms. The model of the tunneling reaction assisted by the local motion of the reactans and products was applied to the temperature dependence of the proton-transfer tunneling reaction (C₆H₆⁻ + C₂H₅OH → C₆H₇ + C₂H₅O⁻) in solid ethanol, the tunneling elimination of H₂ molecule of H₂ molecule ((CH₃)₂ CHCH(CH₃)₂⁺ → (CH₃)₂ C = C(CH₃)₂⁺ + H₂) in solid 2,3-dimethylbutane, and the selective tunneling reaction of H atoms in solid neo-C₅H₁₂-alkane mixtures.     

Excess molar volumes and enthalpies for the binary systems propyl propanoate + o-xylene, m-xylene, and p-xylene at 298.15 K

This paper reports excess molar enthalpies, H_m^E, and excess molar volumes, V_m^E, of the binary systems {propyl propanoate + o-xylene}, {propyl propanoate + m-xylene} and {propyl propanoate + p-xylene} at the temperature 298.15 K and atmospheric pressure, over the whole composition range. V_m^E was calculated from the experimental measurement of the corresponding densities, while H_m^E was measured directly. The excess magnitudes were correlated to a Redlich-Kister type equation. Finally, we will discuss the results of the three mixtures studied here and by comparison with other binary systems containing propyl propanoate and a benzene-based compound previously published.     

Synthesis and molecular structure of the optically active organoaluminium dimer (S)-(—)-(S)-(—)- [(C6H5)CH(CH3)NHA1(CH3)2]2

Reaction of the optically active primary amine (S)-(—)--methylbenzylamine with trimethylaluminium in heptane affords the crystalline organoaluminium dimer (S)-(—)-(S)-(—)-[(C₆H₅)CH(CH₃)NHA1(CH₃)₂]₂. Isolated as large, colourless, extremely air-sensitive prismatic crystals, the title compound crystallizes in the orthorhombic space group P2₁2₁2₁ with unit cell parameters a = 8.406(3), b = 15.505(4), c = 17.547(5) Å, V = 2287 ų and p = 1.03 g cm⁻³ for Z = 4. Least-squares refinement based on 1477 observed reflections converged at R = 0.056, R_w = 0.058. Methane was eliminated during the course of the reaction due to cleavage of A1---C and N---H bonds resulting in an asymmetric A1₂N₂ fragment at the core of the organoaluminium dimer. The mean A1---C bond distance in the dimethylaluminium units is 1.930(8), while the mean A1---N bond distance is 1.950(5) Å. Specific rotation ([]_D²⁵ in CH₂C1₂)of the dimer is determined to be - 20.6°.     

Excess differential thermodynamic properties

A strategy is described for the systematic generation of a complete set of partial derivatives of the four energy functions from a basis set of five measured properties: V_m, S_m, C_p,m (δV_m/δT)_p and either (δV_m/δp)_T or (δV_m/δp)_s. The same set of equations applies to both pure substances and either real or ideal mixtures.

Examples are given of some excess differential properties of binary mixtures which exhibit unusual sensitivity to changes in composition.     

Rate constants for the reaction of OH radicals with CH3CN, C2H5CN AND CH2=CH-CN in the temperature range 298–424 K

Rate constants for the reactions of OH with CH₃CN, CH₃CH₂CN and CH₂=CH-CN have been measured to be 5.86 × 10⁻¹³ exp(−1500 ± 250 cal mole⁻¹/RT), 2.69 × 10⁻¹³ exp(−1590 ± 350 cal mole⁻¹/RT and 4.04 × 10⁻¹² cm³ molecule⁻¹ s⁻¹, respectively in the temperature range 298–424 K. These results are discussed in terms of the atmospheric lifetimes of nitrfles.     

Theoretical studies on the BN substituted fullerenes C70−2x(BN)x (x=1–3)—isoelectronic equivalents of C70

The equilibrium structures and relative stabilities of BN-doped fullerenes C_70−2x(BN)_x (x=1–3) have been studied at the AM1 and MNDO level. The most stable isomers of C_70−2x(BN)_x have been found out and their electronic properties have been predicted. The calculation results show that the BN substituted fullerenes C_70−2x(BN)_x have considerable stabilities, though they are less stable than their all carbon analog. For C₆₈BN, the isomers whose BN is located in the most chemically active bonds of C₇₀ (namely B and A) are among the most stable species, of which B is predicted to be the ground state. The stabilities of C₆₈BN decrease and the dipole moments increase with increasing the distance between the heteroatoms. For C₆₆(BN)₂, the lowest energy species is the isomer in which the B–N–B–N bond is formed; For C₆₄(BN)₃, the most stable species should have three BN units located in the same hexagon to form B–N–B–N–B–N ring. The ionization potentials and the affinity energies of the most stable species of BN-doped C₇₀ are almost the same as those of C₇₀ because of the isoelectronic relationship. The ionization potentials and affinity energies depend on the relative position of the heteroatoms in C₆₈BN, the chemical reactivities of the isomers whose heteroatoms are well separated should differ significantly from their all carbon analog.