Excess enthalpies of ketone+methyl methylthiomethyl sulfoxide or +dimethyl sulfoxide at 298.15 k

Excess enthalpies of sixteen binary mixtures between one each of methyl methylthiomethyl sulfoxide (MMTSO) and dimethyl sulfoxide (DMSO) and one of ketone {CH₃CO(CH₂)_nCH₃, n=0 to 6 and CH₃COC₆H₅} have been determined at 298.15 K. All the mixtures showed positive excess enthalpies over the whole range of mole fractions. Excess enthalpies of ketone+MMTSO or DMSO increased with increasing the number of methylene radicals in the methyl alkyl ketone molecules. Excess enthalpies of MMTSO+ketone are smaller than those of DMSO+ketone for the same ketone mixtures. The limiting excess partial molar enthalpies of the ketone, H ₁ ^E,∞, in all the mixtures with MMTSO were smaller than those of DMSO. Linear relationships were obtained between limiting excess partial molar enthalpies and the number of methylene groups except 2-propanone.     

Excess enthalpies of cycloether + methyl methylthiomethyl sulfoxide or dimethyl sulfoxide at 298.15 K

Excess enthalpies of ten binary mixtures of each of methyl methylthiomethyl sulfoxide (MMTSO) and dimethyl sulfoxide (DMSO) with one of the cycloethers (oxane, 1,3- and 1,4-dioxanes, oxolane and 1,3-dioxolane) have been determined at 298.15 K. All the mixtures show positive excess enthalpies over the whole composition range. Excess enthalpies of the cycloether + MMTSO or DMSO decrease with increasing number of oxygen atoms in the cycloether molecules, except for oxolane + MMTSO. Excess enthalpies of MMTSO + cycloethers are smaller than those of DMSO + cycloethers for the same cycloether except for the 1,3-dioxolane mixtures.

---

Zusammenfassung Bei 298.15 K wurden die Überschußenthalpien von zehn binären Gemischen aus jeweils Methylmethylthiomethylsulfoxid (MMTSO) bzw. Dimethylsulfoxid (DMSO) mit einem der cyclischen Ether (Oxan, 1,3- und 1,4-Dioxan, Oxolan und 1,3-Dioxolan) bestimmt. Alle Gemische zeigen im gesamten Konzentrationsbereich eine positive Überschußenthalpie. Die Überschußenthalpien von Cycloether + MMTSO oder DMSO sinken mit zunehmender Anzahl der Sauerstoffatome im cyclischen Ether, mit Ausnahme von Oxolan + MMTSO. Die Überschußenthalpien für MMTSO + Cycloether sind kleiner als die für DMSO + entsprechender Cycloether, eine Ausnahme bilden die Gemische mit 1,3-Dioxolan.

     

Direct syntheses of Lan+1NinO3n+1 phases (n=1, 2, 3 and ∞) from nanosized co-crystallites

A new direct route for the “bottom up” syntheses of phases in the La_n+1Ni_nO_3n+1 series (n=1, 2, 3 and ∞) has been achieved via single-step heat treatments of nanosized co-crystallized precursors. The co-crystallized precursors were prepared using a continuous hydrothermal flow synthesis system that uses a superheated water flow at ca. 400 °C and 24.1 MPa to produce nanoparticulate slurries. Overall, a significant reduction in time and number of steps for the syntheses of La₃Ni₂O₇ and La₄Ni₃O₁₀ was achieved compared with more conventional synthesis methods, which typically require multiple homogenization and reheating steps over several days.     

Thermodynamic investigations on derivatives of pyrimidine nucleic acid bases: Joint use of calorimetric, volumetric and structural data for the description of properties of pyrimidine nucleic acid bases and their derivatives

The experimental enthalpies of solution Δ_solH_m^∞, van’t Hoff enthalpies of sublimation Δ_s^gH_m⁰ of solid compounds, partial molar volumes V₂⁰, and partial molar heat capacities C_p,2⁰ of aqueous solutions of pyrimidine nucleic acid bases and their derivatives, determined previously and collected here, are discussed in terms of calculated structural parameters. Relations have been established between the calorimetric and volumetric properties. Correlations have been developed to relate both the enthalpies of solvation and the partial molar heat capacities to the polar and apolar parts of the accessible molecular surface areas.     

Intercalation behavior of n-alkylamines into an A-site defective layered perovskite H2W2O7

Intercalation behavior of n-alkylamines into a protonated form of an A-site defective layered perovskite H₂W₂O₇ has been investigated. Results from XRD indicate these materials are layered with the corresponding interlayer spacing governed by the n-alkylamine chain length, and a reversible intercalation and deintercalation property is observed among these intercalation compounds. The IR spectra of the intercalation compounds with n-alkylamines clearly show that n-alkyl chains possess an all-trans conformation, and H₂W₂O₇ accommodate n-alkylamines (C_nH_2n+1NH₂: n=3, 4, 7, 8, 12, 16) to form intercalation compounds via an acid-base mechanism. A linear relationship between the interlayer distance and the number of carbon atoms in n-alkyl chains is observed to show a bilayer arrangement of the n-alkyl chains with a tilt angle of ∼71.6°. Elemental analysis studies reveal that the amounts of intercalated n-alkylamines are about 2.0 mol per [W₂O₇]. Despite the surface geometry of H₂W₂O₇ is almost identical to those of layered perovskites H₂[A_n−1B_nO_3n+1], the amounts of intercalated n-alkylamines of them are different. A reasonable explanation is given through our research.     

Synthesis and characterization of n=5, 6 members of the La4Srn−4TinO3n+2 series with layered structure based upon perovskite

Layered compounds have been synthesized and structurally characterized for the n=5 and 6 members of the perovskite-related family La₄Sr_n−4Ti_nO_3n+2 by combining X-ray diffraction and transmission electron microscopy. Their structure can be regarded as comprising [(La,Sr)₅Ti₅O₁₇] and [(La,Sr)₆Ti₆O₂₀] perovskite blocks joined by crystallographic shears along the a-axis, with consecutive blocks shifted by 1/2 [100]_p. The n=5 member is similar to the previously reported n=5 member of other A_nB_nO_3n+2-related series. The n=6 member, which has only been briefly reported in other systems previously, is also a well-behaved member of this A_nB_nO_3n+2 series.     

Transmission electron microscopy study of Ruddlesden-Popper Can+1MnnO3n+1n=2 and 3 compounds

Two Ruddlesden-Popper compounds Ca_n+1Mn_nO_3n+1 with n=2 and 3 synthesized by a citrate gel technique have been studied by TEM. The structure of Ca₄Mn₃O₁₀ is consistent with the previously determined structure having the space group Pbca and a⁻ a⁻ c⁺/a⁻ a⁻ c⁺ tilt system. The presence of defects suggests the possible high-temperature phase transition from untilted I4/mmm to Pbca. The structure of Ca₃Mn₂O₇ was found to be different from the previously suggested I4/mmm symmetry. Ca₃Mn₂O₇ forms with an orthorhombic structure with either Cmcm or Cmc2₁ space group. A structural model for Cmc2₁ based on the tilting of almost-rigid octahedra with a⁺ c⁻ c⁻/a⁺ c⁻ c⁻ tilt system is proposed. The lamellar defects were shown to be twin variants of the Cmc2₁ structure with the (001)_t interfaces, which suggests the possible tilting phase transition from the ideal I4/mmm to Cmc2₁ following the maximal group-subgroup symmetry tree: I4/mmm→Fmmm→Bbmm(Cmcm)→Bb2₁m(Cmc2₁).     

Synthesis and structure of a 1,6-hexyldiamine heptaborate, [H3N(CH2)6NH3][B7O10(OH)3]

A new 1,6-hexyldiamine heptaborate, [H₃N(CH₂)₆NH₃][B₇O₁₀(OH)₃] (1), has been solvothermally synthesized and characterized by single-crystal X-ray diffraction, FTIR, elemental analysis, and thermogravimetric analysis. Compound 1 crystallizes in monoclinic system, space group P2₁/n with a=8.042(2) Å, b=20.004(4) Å, c=10.103(2) Å, and β=90.42(3)°. The anionic [B₇O₁₀(OH)₃]_n²ⁿ⁻ layers are interlinked via hydrogen bonding to form a 3D supramolecular network containing large channels, in which the templated [H₃N(CH₂)₆NH₃]²⁺ cations are located.     

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.     

Cl/Cl isotope effects in Rh NMR of [RhCln(H2O)6−n] complex anions in hydrochloric acid solution as a unique ‘NMR finger-print’ for unambiguous speciation

A detailed analysis of the ³⁵Cl/³⁷Cl isotope effects observed in the 19.11 MHz ¹⁰³Rh NMR resonances of [RhCl_n(H₂O)_6−n]³⁻ⁿ complexes (n = 3–6) in acidic solution at 292.1 K, shows that the ‘fine structure’ of each ¹⁰³Rh resonance can be understood in terms of the unique isotopologue and in certain instances the isotopomer distribution in each complex. These ³⁵Cl/³⁷Cl isotope effects in the ¹⁰³Rh NMR resonance of the [Rh^35/37Cl₆]³⁻ species manifest only as a result of the statistically expected ³⁵Cl/³⁷Cl isotopologues, whereas for the aquated species such as for example [Rh^35/37Cl₅(H₂O)]²⁻, cis-[Rh^35/37Cl₄(H₂O)₂]⁻ as well as the mer-[Rh^35/37Cl₃(H₂O)₃] complexes, additional fine-structure due to the various possible isotopomers within each class of isotopologues, is visible. Of interest is the possibility of the direct identification of stereoisomers cis-[RhCl₄(H₂O)₂]⁻, trans-[RhCl₄(H₂O)₂]⁻, fac-[RhCl₃(H₂O)₃] and mer-[RhCl₃(H₂O)₃] based on the ¹⁰³Rh NMR line shape, other than on the basis of their very similar δ(¹⁰³Rh) chemical shift. The ¹⁰³Rh NMR resonance structure thus serves as a novel and unique ‘NMR-fingerprint’ leading to the unambiguous assignment of [RhCl_n(H₂O)_6−n]³⁻ⁿ complexes (n = 3–6), without reliance on accurate δ(¹⁰³Rh) chemical shifts.     

Excess molar enthalpies of {(1 − x2 − x3)Al + x2Bi + x3Ga}(I) alloys

The excess molar enthalpies H_m^E{(1 ? x₂ ? x₃)Al + x₂Bi + x₃Ga}(I) have been measured between 725 and 1170 K along the sections $\text{(1 ? x}{}_2\text{? x}{}_3\text{)}\text{x}{}_3\text{=}\text{1}\text{3}$, 1, and 3, and $\text{x}{}_2\text{x}{}_3\text{=}\text{1}\text{3}$, 1, and 3, with a high-temperature Calvet calorimeter using both the direct- and indirect-drop methods of mixing; experimental uncertainty is quoted respectively at 6.7 per cent and 9.9 per cent. The equilibrium temperatures confirmed phase boundaries previously determined by potentiometry, d.t.a., and calculation. Extrapolation of the experimental excess molar enthalpies to the limiting binary alloys {(1 ? x₂)Al + x₂Bi} allows new values for the excess molar enthalpies of these alloys to be proposed. The excess molar enthalpies of the ternary liquid mixtures can be represented correctly using these new values and Bonnier's equation.     

Salt Effects on Volumetric Properties of Some n-Alkoxyethanols (C1Em, m = 1, 2, and 3) in Aqueous Solutions at 298.15 K

Accurate density measurements over the whole composition range were made at a temperature of 298.15 K under ambient pressure for the mixtures of ethylene glycol monomethyl ether (2-methoxyethanol, C₃H₇O₂; C₁E₁), or diethylene glycol monomethyl ether (2-(2-methoxyethoxy)ethanol, C₅H₁₂O₃; C₁E₂), or triethylene glycol monomethyl ether [2-{2-(2-methoxyethoxy)ethoxy}ethanol, C₇H₁₆O₄; C₁E₃) in aqueous salt solutions having a common anion with a view to examining the cationic effect on the volumetric properties. To gain insight into the mixing behavior, results of the density measurements were used to estimate excess molar volumes, V_m^E, apparent molar volumes, V_{, i}, partial molar volumes, , excess partial molar volumes, V_m,i^E, and their limiting values at infinite dilution, V_{, i}, V_m,i, and V_m,i^E,, respectively. Aqueous solutions of the chlorides of lithium, sodium, potassium, and calcium in a concentration range to ca. 1 mol-kg^–1 were chosen for investigation as this concentration is used most frequently in applied chemistry. All mixtures except that containing lithium chloride show a decrease in the magnitude of V_m^E with the addition of a salt when compared to salt-free mixtures. Comparison of the derived volumes at infinite dilution suggested modification of the water structure as well as an electrostatic interaction between the ionic species and an alkoxyethanol molecule.     

Change in mechanistic pathway of hydroboration: A detailed kinetic study of H2BBr·SMe2 and HBBr2·SMe2

Hydroboration reactions of 1-octene and 1-hexyne with H₂BBr·SMe₂ in CH₂Cl₂ were studied as a function of concentration and temperature, using ¹¹B NMR spectroscopy. The reactions exhibited saturation kinetics. The rate of dissociation of dimethyl sulfide from boron at 25 °C was found to be (7.36 ± 0.59 and 7.32 ± 0.90) × 10⁻³ s⁻¹ for 1-octene and 1-hexyne, respectively. The second order rate constants, k₂, for hydroboration worked out to be 7.00 ± 0.81 M s⁻¹ and 7.03 ± 0.70 M s⁻¹, while the overall composite second order rate constants, k K, were (3.30 ± 0.43 and 3.10 ± 0.37) × 10⁻² M s⁻¹, respectively at 25 °C. The entropy and enthalpy values were found to be large and positive for k₁, whilst for k₂ these were large and negative, with small values for enthalpies. This is indicative of a limiting dissociative (D) for the dissociation of Me₂S and associative mechanism (A) for the hydroboration process. The overall activation parameters, ΔH^≠ and ΔS^≠, were found to be 98 ± 2 kJ mol⁻¹ and +56 ± 7 J K⁻¹ mol⁻¹ for 1-octene whilst, in the case of 1-hexyne these were found out to be 117 ± 7 kJ mol⁻¹ and +119 ± 24 J K⁻¹ mol⁻¹, respectively. When comparing the kinetic data between H₂BBr·SMe₂ and HBBr₂·SMe₂, the results showed that the rate of dissociation of Me₂S from H₂BBr·SMe₂ is on average 34 times faster than it is in the case of HBBr₂·SMe₂. Similarly, the rate of hydroboration with H₂BBr·SMe₂ was found to be on average 11 times faster than it is with HBBr₂·SMe₂. It is also clear that by replacing a hydrogen substituent with a bromine atom in the case of H₂BBr·SMe₂ the mechanism for the overall process changes from limiting dissociative (D) to interchange associative (I_a).     

Hydrothermal synthesis, characterization and thermochemistry of Ca2[B2O4(OH)2]·0.5H2O

A pure calcium borate Ca₂[B₂O₄(OH)₂]·0.5H₂O has been synthesized under hydrothermal condition and characterized by XRD, FT-IR and TG as well as by chemical analysis. The molar enthalpy of solution of Ca₂[B₂O₄(OH)₂]·0.5H₂O in HC1·54.582H₂O was determined. From a combination of this result with measured enthalpies of solution of H₃BO₃ in HC1·54.561H₂O and of CaO in (HCl + H₃BO₃) solution, together with the standard molar enthalpies of formation of CaO(s), H₃BO₃(s) and H₂O(l), the standard molar enthalpy of formation of −(3172.5 ± 2.5) kJ mol⁻¹ of Ca₂[B₂O₄(OH)₂]·0.5H₂O was obtained.     

Isotopic substitution effects on the volumetric and viscosimetric properties of water-dimethylsulfoxide mixtures at 25°C

Densities and viscosities of binary mixtures (H₂O or D₂O) (1) + (DMSO or DMSO-D6)(2) have been measured over the entire mole fraction range; and the excess volumes, excess viscosities, and excess partial molar volumes Vf of the components have been obtained. All systems show negative excess volume V^e at all compositions, values for mixtures containing D₂O being more negative than those with H₂O byca. 0.03 cm³-mol^-1 at x₁, = 0.6, where a minimum is observed. The difference between DMSO and DMSO-D6 containing mixtures is negligible. The excess viscosity η^e is always positive and shows a maximum at x₁ = 0.65; at this composition, the substitution of H₂O with D₂O causes an excess viscosity increment ofca. 0.35 mPa-s, while deuteration of DMSO brings about a smaller increase,ca. 0.1 mPa-s. The trend of V ₂ ^E with concentration shows the characteristic features of moderately hydrophobic solutes in water (negative values and a minimum in the water-rich region), features that are slightly but significantly more marked in D₂O than in H₂O. The V ₂ ^E values in the water-diluted region and at x₁, =0 are more negative for D₂O than for H₂O.     

Thermodynamic study of 2-methyl-tetrahydrofuran with isomeric chlorobutanes

Excess molar volumes, V^E, isentropic compressibility deviations, Δκ_S, and excess molar enthalpies, H^E, for the binary mixtures 2-methyl-tetrahydrofuran with 1-chlorobutane, 2-chlorobutane, 2-methyl-1-chloropropane and 2-methyl-2-chloropropane have been determined at temperatures 298.15 and 313.15 K, excess molar enthalpies were only measured at 298.15 K. We have applied the Prigogine-Flory-Patterson (PFP) theory to these mixtures at 298.15 K.     

Crystal Structure of Pseudorhombohedral InFe1−xTixO3+x/2 (x=2/3)

The structure of pseudorhombohedral-type InFe_1−xTi_xO_3−x/2 (x=2/3) was refined by Rietveld profile fitting. The crystal is a commensurate member of a series in a solution range on InFeO₃-In₂Ti₂O₇ including incommensurate structures. The structure with the unit cell of a=5.9188(1), b=10.1112(2), and c=6.3896(1) Å, β=108.018(2)°, and a space group P2₁/a is the alternate stacking of an edge-shared InO₆ octahedral layer and an Fe/Ti-O plane along c^*. Metal sites on the Fe/Ti-O plane are surrounded by four oxygen atoms on the Fe/Ti-O plane and two axial ones. Electric conductivities of the order 10⁻⁴ S/cm were observed for the samples at 1000 K, while the oxide ion transport number is almost zero as no electromotive force was detected by an oxygen concentration cell.     

Crystal chemistry of M[PO2(OH)2]2·2H2O compounds (M=Mg, Mn, Fe, Co, Ni, Zn, Cd): Structural investigation of the Ni, Zn and Cd salts

The compounds M[PO₂(OH)₂]₂·2H₂O (M=Mg, Mn, Fe, Co, Ni, Zn, Cd) were prepared from super-saturated aqueous solutions at room temperature. Single-crystal X-ray structure investigations of members with M=Ni, Zn, Cd were performed at 295 and 120 K. The space-group symmetry is P2₁/n, Z=2. The unit-cell parameters are at 295/120 K for M=Ni: a=7.240(2)/7.202(2), b=9.794(2)/9.799(2), c=5.313(1)/5.285(1) Å, β=94.81(1)/94.38(1)°, V=375.4/371.9 Å³; M=Zn: a=7.263(2)/7.221(2), b=9.893(2)/9.899(3), c=5.328(1)/5.296(2) Å, β=94.79(1)/94.31(2)°, V=381.5/377.5 Å³; M=Cd: a=7.356(2)/7.319(2), b=10.416(2)/10.423(3), c=5.407(1)/5.371(2) Å, β=93.85(1)/93.30(2)°, V=413.4/409.1 Å³. Layers of corner-shared MO₆ octahedra and phosphate tetrahedra are linked by three of the four crystallographically different hydrogen bonds. The fourth hydrogen bond (located within the layer) is worth mentioning because of the short O_h?O bond distance of 2.57-2.61 Å at room temperature (2.56-2.57 Å at 120 K); only for M=Mg it is increased to 2.65 Å. Any marked temperature-dependent variation of the unit-cell dimension is observed only vertical to the layers. The analysis of the infrared (IR) spectroscopy data evidences that the internal PO₄ vibrations are insensitive to the size and the electronic configuration of the M²⁺ ions. The slight strengthening of the intra-molecular P-O bonds in the Mg salt is caused by the more ionic character of the Mg-O bonds. All IR spectra exhibit the characteristic “ABC trio” for acidic salts: 2900-3180 cm⁻¹ (A band), 2000-2450 cm⁻¹ (B band) and 1550-1750 cm⁻¹ (C band). Both the frequency and the intensity of the A band provide an evidence that the PO₂(OH)₂ groups in M[PO₂(OH)₂]₂·2H₂O compounds form weaker hydrogen bonds as compared with other acidic salts with comparable O?O bond distances of about 2.60 Å. The observed shift of the O-H stretching vibrations of the water molecule in the order M=Mg>Mn≈Fe≈Co>Ni>Zn≈Cd has been discussed with respect to the influence of both the character and the strength of M↔H₂O interactions.     

Synthesis, structure and magnetic properties of the S=1/2, one-dimensional antiferromagnet, Y5Re2O12

Single crystals of Y₅Re₂O₁₂ have been grown, and the crystal structure has been determined by X-ray diffraction. This compound crystallizes in space group C2/m with cell dimensions of a=12.4081(10) Å b=5.6604(5)Å, c=7.4951(6) Å, β=107.837(3)°, Z=2. The final refinement led to R1=0.0238, WR2=0.0459 for 1053 observed reflections with F>4σ(F₀). Edge-sharing ReO₆ octahedra form infinite linear [ReO₂O_4/2]_n chains along the b direction with alternating short and long Re-Re distances. Three crystallographically independent yttrium atoms surround O2 to form OY₄ tetrahedra, which share edges and corners in the ab plane to form a two-dimensional Y₅O₄ network which separates the [ReO₂O_4/2]_n magnetic chains. This compound is therefore isostructural with the series Ln₅Re₂O₁₂Ln=Gd-Lu, which have been known since 1969. The average Re oxidation state is +4.5 in the chains and a reasonable, if qualitative MO scheme results in one unpaired electron per Re dimer. Consistent with this, magnetic susceptibility data can be fitted to the one-dimensional antiferromagnetic Heisenberg model with S=1/2 and parameters J^intra/k=−89(1)K, g=2.15(4) and χ(TIP)=5(1)×10⁻⁴ emu/mol. There is no sign of long-range magnetic order down to 2 K. These results are contrasted with those for the isostructural Y₅Mo₂O₁₂.     

Oxygen nonstoichiometry (δ) of TiO2−δ-revisited

Oxygen nonstoichiometry (δ) of “undoped” polycrystalline TiO_2−δ has been measured as a function of oxygen partial pressure in the widest ever examined range of 10^-18?P_O2/atm?10^-1 at elevated temperatures (1073?T/K?1473) by thermogravimetry and coulometric titrometry combined and compared with all the reported values. Isothermal variation of nonstoichiometry against P_O2 is explained with a defect model involving quadruply ionized titanium interstitials, electrons, holes, and unidentified acceptors which may be background impurity acceptors or cation vacancies. The equilibrium constants for intrinsic electronic excitation reaction and redox reaction are determined from the nonstoichiometry measured and compared exhaustively with all the reported values. The relative partial molar enthalpy and entropy of oxygen are evaluated as functions of nonstoichiometry and the inner workings of their variations discussed.