Excess enthalpies of some aromatic aldehydes in n-hexane, n-heptane and benzene

Calorimetric measurements of molar excess enthalpies, H^E, at 298.15 K, of mixtures containing aromatic aldehydes of general formula C₆H₅(CH₂)_mCHO (with m = 0, 1 and 2) + n-hexane, n-heptane or benzene are reported, together with the values of H^E at equimolar composition compared with the corresponding values of H^E for the aromatic ketones in the same solvents. The experimental results clearly indicate that the intermolecular interactions between the carbonyl groups (CHO) are influenced by the intramolecular interactions between the carbonyl and phenyl groups, particularly for the mixtures containing benzaldehyde.     

Phase behavior of Li2WO4 at high pressures and temperatures

The phase diagram of Li₂WO₄, previously studied by Yamaoka et al. (J. Solid State Chem.6, 280 (1973)) has been revised. Li₂WO₄ II is stable at atmospheric pressure below ～310°C. This phase appears to be a modified spinel, and is tetragonal, a, c = 11.941, 8.409Å, Z = 16, space group $\text{I4}{}_1\text{amd}$. The melting curve of phenacite-type Li₂WO₄ I rises with pressure with a slope of 0.9°C/kbar to the III/I/liquid triple point at 3.1 kbar, 743°C, beyond which the melting curve of orthorhombic Li₂WO₄ III rises steeply with pressure (initial slope 31°C/kbar). The Li₂WO₄$\text{I}\text{III}$ transition line at 3 kbar is almost independent of temperature, i.e., the $\text{I}\text{III}$ transition entropy is zero. Li₂WO₄ II is 21.3% denser than Li₂WO₄ I at ambient conditions.     

Low-frequency Raman-active vibrations of triclinic n-paraffins

The low-frequency Raman spectra of triclinic n-paraffins, n-C₈H₁₈ through n-C₂₄H₅₀, were observed. The normal-coordinate treatments of crystal vibrations of n-C₈H₁₈ through n-C₁₈H₃₈ were carried out. Six characteristic series of the observed Raman lines were assigned to rotatory lattice vibrations and intramolecular skeletal vibrations.     

Phases and phase transitions of compounds (CnH2n+1NH3)2MnCl4 with n = 1, 2, 3

Phases and structural phase transitions of the compounds (CH₃NH₃)₂MnCl₄, (C₂H₅NH₃)₂MnCl₄ and (C₃H₇NH₃)₂MnCl₄ have been studied by means of thermoanalytical methods (DSC) and X-ray single crystal and powder diffraction data in the temperature range of 85–480°K at normal pressure. All phases show perovskite-like layer structures. The high temperature phases (α phase) correspond to the K₂NiF₄ type and may be regarded as the aristotype of each polymorphic compound. All transitions are reversible. Transition patterns are:

Based on the DSC peak-shape analysis and diffraction data a model of a tilting system of the MnCl₆-octahedra layer is introduced in order to understand essential features of structures of different phases and their transition behavior. Single crystal film data of (C₃H₇NH₃)₂MnCl₄ phases reveal some disorder phenomena. The ε phase exhibits a superstructure along [010] with a triplication of the shortest axis corresponding to the δ phase. The γ phase of this compound shows strong satellite reflections, due to a transverse distortion wave along the [100] lattice direction.     

Ternary interaction parameters in n-hexane/butanone (MEK)/poly(dimethylsiloxane) (PDMS) and n-heptane/MEK/PDMS systems

Second virial coefficients, A₂, intrinsic viscosities, [η], and solvation preferential coefficients, γ, for the ternary systems n-hexane, HEX, (1)/butanone, MEK, (2)/poly(dimethylsiloxane), PDMS, (3) and n-heptane, HEP, (1)/MEK (2)/PDMS (3) have been determined at 20.0°. Binary interaction parameters, g₂, have also been measured by light scattering. Inversion in γ at $\text{u}{}_2\text{? 0.15}$ in the HEX system and at $\text{u}{}_2\text{? 0.22}$ in the HEP system takes place. The inversion points are accompanied by smooth maxima in A₂ and in [η]. Both systems show a weak cosolvent character. Theoretical γ's derived, according to Flory-Huggins and Flory-Prigogine-Patterson, are compared with experimental values. The evaluation of the ternary interaction potential, g_T, and its dependence on system composition allow evaluation of the binary interaction potentials and their dependence on polymer concentration.     

The isostructural γ-sulfur phase of selenium-sulfur,SenS8−n

Two new selenium-sulfur species, Se_1.1S_6.9 (yellow) and Se_3.7S_4.3 (orange), have been isolated as single crystals, and the corresponding structures have been determined. The space group is P2c, and the parameters are a = 8.34 A?, b = 13.11 A?, c = 9.30 A?, β = 123.9° and a = 8.40 A?, b = 13.26 A?, c = 9.37 A?, β = 124.5°, respectively. They are isostructural with γ-sulfur, having two distinct pairs of eight membered rings in the unit cell. The selenium and sulfur atoms appear scrambled throughout all atomic positions, but are not scrambled equally. When atomic site occupancy data are combined with other data from the literature, a wide compositional continuum of γ-sulfur isostructures is revealed that extends from γ-sulfur to SeS. It appears unlikely that selenium-sulfur crystals exist having the γ-sulfur structure with more than half the atoms as selenium.     

The system NiAl2O4Ni2SiO4 at high pressures and temperatures: Spinelloids with spinel-related structures

Phase relations in the system NiAl₂O₄Ni₂SiO₄ were studied in the pressure range 1.5 ～ 13.0 GPa and in the temperature range 800 ～ 1450°C. Two new phases, IV and V, were found in regions of pressure higher than 4 GPa. Phase V disproportionates into a mixture of Ni₂SiO₄-spinel, NiO, and Al₂O₃ at approximately 9.5 GPa and 1100°C. Phases III, IV, and V form a solid solution in some compositional range: phases IV and V have a composition around NiAl₂O₄·Ni₂SiO₄, whereas phase III spreads from NiAl₂O₄·Ni₂SiO₄ to the NiAl₂O₄-rich side. All the phases I ～ V are structurally considered to be spinel derivatives, “spinelloids,” with three kinds of tetrahedral groups; isolated tetrahedra TO₄, linked ones T₂O₇, and triply linked ones T₃O₁₀. The ratios of isolated tetrahedra to linked ones are large in the higher-pressure phases and small in the lower-pressure phases. The difference of compositional range of phase III from that of phases IV and V is possibly explained by the avoidance of linked tetrahedra such as O₃AlOAlO₃.     

Anionic polymerization of methacrylonitrile—I. Polymerization with n-butyllithium as initiator

The anionic polymerization of methacrylonitrile has been studied at ?75° in toluene and with n-butyllithium as initiator. The kinetics of the polymerization were investigated considering the consumption of both monomer and initiator. BuLi disappears relatively slowly and about 50–60% remains unreacted. A simple kinetic scheme cannot therefore be put forward. All possible side reactions have also been examined. The molecular weight study establishes the living character of this system and gives an initiator efficiency of about 0.2. The contribution of low molecular weight products, typical of the polymerization of polar monomers, is also taken into account. In order to obtain a better understanding of the mechanism of this polymerization, in which unreacted initiator is probably engaged in very stable and inactive mixed associated particles, small amounts of THF (known frequently to break down such aggregates) were added to the system. A rather unexpected slow but complete disappearance of the initiator occurs; the conversion at which the rate of monomer consumption levels off depends on the THF concentration.     

Enthalphy of mixing of bromobenzene with n-alkanes,with cyclohexane,and with benzene

A dynamic flow microcalorimeter of the Picker design was used to measure enthalpies of mixing at 298.15 K and atmospheric pressure of the six binary systems bromobenzene + n-hexane, + n-heptane, + n-nonane, + n-tetradecane, + cyclohexane, and + benzene. Within the homologous series of n-alkane systems, the interaction parameter, h₁₂, calculated from rigid-lattice group contribution theory, decreases weakly with increasing chain length of the alkane. This behavior is quite analogous to that observed with chloro-derivatives of benzene + n-alkane.     

Low-frequency intramolecular and lattice vibrations of n-C36H74 as studied by Raman scattering

The Raman spectrum of n-C₃₆H₇₄ has been measured in the region between 0 and 150 cm^?1. Eleven newly observed bands have been assigned to the intramolecular skeletal vibrations and rotatory lattice vibrations on the basis of the dispersion curves calculated previously.     

A new enthalpy-increment calorimeter enthalpy increments for n-hexane

A water-cooled heat-exchange calorimeter for the measurement of enthalpy increments of fluids up to 700 K and 15 MPa has been constructed. Novel features of the design ensure that heat leaks are small, well controlled, and easily measured. The results of 90 test runs on steam gave enthalpy increments in agreement with steam tables to within 0.5 per cent. The calorimeter has been used to measure enthalpy increments of n-hexane up to 573.2 K and 12.67 MPa, and the results are compared with the Starling modification of the BWR equation of state. Overall agreement of 115 measurements with the BWRS equation is 0.97 per cent. In the critical region BWRS values differ from experiment by up to 4 per cent.     

Excess heat capacities of binary mixtures of carbon tetrachloride with n-alkanes at 298.15 K

A Picker flow microcalorimeter was used to determine molar excess heat capacities C_P^E at 298.15 K for mixtures of carbon tetrachloride + n-heptane, n-nonane, and n-decane. The excess heat capacities are negative in all cases. The absolute value |C_P^E| increases with increasing chain length of the alkane. A formal interchange parameter, c_P12, is calculated and its dependence on n-alkane chain length is discussed briefly in terms of molecular orientations.     

Structural investigation of K+ and Tl+ β-aluminas

Structures of K⁺ and Tl⁺ aluminas were investigated by single-crystal X-ray diffraction. In the final refinements, corresponding to R values of 0.034 and 0.058, respectively, the distribution of conducting ions was found to be similar to that of Na β-alumina. In K⁺ β-alumina clear evidence of additional electronic density in the spinel-like blocks is obtained and is interpreted as due to a Frenkel defect.     

Closo clusters with unusual electron numbers: Localized bond schemes for n-atom clusters with n, (n + 1) or (n + 2) skeletal electron pairs

This paper considers whether satisfactory localized 2- and 3-centre bond schemes may be devized for real or hypothetical clusters B_nH_n^c? (c = 0, 2 or 4; n = 4 → 12) or isoelectronic analogues thereof, with closo deltahedral shapes. As expected, localized bond schemes can be devized for all the species that would be predicted, using MO approaches, to have closed shell electronic configurations: these include species B_nH_2? (n = 5 → 12) and B_nH_n^c? (c = 0 or 4; n = 4, 8, 9 or 11). There is also generally good agreement with MO treatments as to which systems are not expected to be stable: these include B₄H₄^2? and B_nH_n^c? (c = 0 or 4; n = 5, 7 or 10). Localized bond treatments have value for estimating the bond orders of cluster bonds in species B_nH_n and B_nH_n^2?, though they overestimate the bond orders in species B_nH_n^4? (except when n = 4). They are misleading, when applied to octahedral and icosahedral systems, in indicating the former shape to be feasible for hypothetical species B₆H₆ and B₆H₆^4?, and the latter shape to be feasible for hypothetical species B₁₂H₁₂ and B₁₂H₁₂^4?.     

The system BaOGeO2 at high pressures and temperatures,with special reference to high-pressure transformations in BaGeO3, BaGe2O5, and Ba2Ge5O12

Phase relations in the system BaOGeO₂ were investigated in the pressure range 20–70 kbar in the temperature range 750–1200°C. Several new phases were identified in this system: an atmospheric phase of BaGe₂O₅ (monoclinic BaGe₂O₅ I), two high-pressure phases of BaGe₂O₅ (monoclinic BaGe₂O₅ II and tetragonal BaGe₂O₅ III), and a high-pressure phase of Ba₂Ge₅O₁₂. The phase boundary curve between BaGe₂O₅ II and BaGe₂O₅ III was preliminarily determined as P(kbar) = 7.7 + 0.047T (°C). The high-pressure phases of BaGeO₃, which were previously reported by Y. Shimizu, Y. Syono, and S. Akimoto (High Temp.-High Pressures2, 113 (1970)) in the pressure range 15–95 kbar, were interpreted to be not single-phase materials but complicated mixtures of more than two phases in the system BaOGeO₂. X-Ray powder diffraction data for the new compounds synthesized in this study are given.     

The influence of Ni2+ lons on the distribution of Mg2+ and Cu2+ lons in spinel ferrites

Cation distribution in quenched and furnace-cooled samples of composition Ni_xM_1?xFe₂O₄ (where M is either Mg²⁺ or Cu²⁺) has been studied through magnetization measurements. It has been found that cation distribution in these mixed ferrites cannot be predicted by site preference energies. In magnesium-nickel ferrites, cation distribution is controlled by heat treatment up to x = 0.5, beyond which the effect of heat treatment diminishes. Addition of Ni²⁺ ions in copper ferrite reduces the diffusibility of Cu²⁺ ions and the distribution tends toward inverse spinel in the high-nickel region.     

Unusual influences of temperature and medium on the tacticity of radically polymerised poly(n-vinyl imidazole)

The tacticities of radical poly(N-vinyl imidazole)s prepared in several organic solvents, in water and at various values of pH and temperature have been investigated by ¹H and ¹³C-NMR. It seems most likely that high temperatures favour racemic placements over meso placements but that, at low pH, meso placements are favoured. Thus the changes in polymerisation rate with pH noted by others for this system are accompanied by changes in the stereochemistry of the resulting polymer.     

Isothermal vapor-liquid equilibrium data for the ethane—carbon dioxide system at high pressures

Isothermal vapor-liquid equilibrium data for the ethane—carbon dioxide system at high pressures were obtained at 10, 15, 18, 20, and 25°C.The gas-liquid critical data (pressure—temperature—composition) for the system were also measured at several temperatures, and the azeotropic points were obtained at 10, 15, and 18°C. This system exhibits two critical points and one azeotropic point in the temperature range from 17.5°C to 18.5°C.     

The SO+2 radical-ion

From the complex overall EPR spectrum of ⁶⁰Co gamma-irradiated pure solid sulfur dioxide the spectrum of the SO⁺₂ radical-ion was selected and the following principal values for the g-tensor obtained: g₁ = 1.9620;g₂ = 2.0026;g₃ = 2.0118 (Δg = ± 0.0005).