Topological and thermodynamic investigations of molecular interactions in binary mixtures: Molar excess volumes and molar excess enthalpies

Molar excess volumes and molar excess enthalpies of butyl acetate (i) with cyclohexane or benzene or toluene or o-, m- or p-xylene (j) binary mixtures have been measured dilatometrically and calorimetrically over the entire composition range at 308.15 K. The observed data have also been analyzed in terms of graph theoretical approach. The analysis of V^E data by graph theoretical approach suggests that butyl acetate in pure state exists as associated entity and (i + j) mixtures are characterized by the presence of (i–j) molecular entity. It has further been observed that V^E and H^E values calculated by this approach agree well with the corresponding experimental values. The presence of molecular entity is further confirmed by IR study of (i + j) mixture.     

Evaluating physical properties of molten salt reactor fluoride mixtures

In the last years, interest in the use of high-temperature molten fluoride salts as fluid fuels and coolants in nuclear power systems has been increasing. The comprehensive information on the properties of molten fuel and coolant salts is necessary for development of new designs. Experimental data on physical properties of some prospective molten salt mixtures of Li, Na, Be, Zr fluorides containing fertile and fissile materials as well as soluble fission products are unknown. At the first stage of the conceptual development estimation of the required properties from the known experimental data can be useful for selection of suitable molten salt compositions. In this paper the approaches for estimation of the physicochemical properties such as density (ρ), dynamic viscosity (η), isobaric heat capacity (c_p), and thermal conductivity (λ) for molten salt fluoride mixtures are proposed. The calculation algorithm was based on the additivity principle for the properties (P_x) of multi-component molten salt mixtures, which can be found from the relationship P_x = ΣN_iP_i. Here N_i and P_i denote mole fraction and corresponding property of individual molten salts or their binary mixtures as constituents of the more complex systems. The empirical expressions connecting the property with molar volume and molecular mass of selected fluoride compositions are also derived and tested. Estimated values are compared with each other and available experimental data.     

Local structural analyses on molten terbium fluoride in lithium fluoride and lithium-calcium fluoride mixtures

X-ray absorption fine structure (XAFS) measurements on terbium fluoride in molten lithium fluoride and in molten lithium-calcium fluoride mixtures, (e.g. 0.20TbF₃-0.80LiF, 0.20TbF₃-0.62LiF-0.18CaF₂, 0.20TbF₃-0.48LiF-0.32CaF₂, 0.50TbF₃-0.50LiF, and 0.50TbF₃-0.38LiF-0.12CaF₂), have been carried out. In the solid state, coordination number of terbium (N_i) and inter ionic distances between terbium and fluorine in the first neighbor (r_i) are nearly constant in all mixtures. In 0.20TbF₃-0.80LiF, 0.20TbF₃-0.62LiF-0.18CaF₂ and 0.50TbF₃-0.50LiF mixtures, N_i's decrease from ca. 8 to 6 and r_i's also decrease from ca. 2.29 to 2.26 Å on melting. On the other hands, in molten 0.20TbF₃-0.48LiF-0.32CaF₂ and 0.50TbF₃-0.38LiF-0.12CaF₂ mixtures, N_i's are slightly larger than 6 and r_i's do not change. These facts correspond to the amount of F⁻ supplied by solvent melts, i.e. the effect of CaF₂ becomes predominant at bCaF₂ > 0.32 in ternary 0.20TbF₃-aLiF-bCaF₂ mixtures and at bCaF₂ > 0.12 in ternary 0.50TbF₃-aLiF-bCaF₂ mixtures.     

Molar excess volumes of ternary mixtures of nonelectrolytes

Molar excess volumes V^E_ijk of methylenebromide i + pyridine j + β-picoline (k, cyclohexane (i) + pyridine (j) + β-picoline(K), benzene(i)+toluene(j)+1,2-dichloroethane(k), benzene(i) + 0-xylene(j) + 1,2-dichloroethane(k) and benzene(i) + p-xylene(j) + 1,2-dichloroethane(k) mixtures have been determined dilatometrically at 298.15 K. The data have been examined in terms of Sanchez and Lacombe theory and the graph-theoretical approach, and it is found that they are described well by the latter. Self- and cross-volume interaction coefficients V_jk, V_jjk and V_jkk, etc., have also been evaluated and the values utilised to study molecular interactions between the jth and kth molecular species in the presence of the ith in these i + j + k mixtures.     

Structure and molecular interactions in {ethanol + (propan-1-ol/propan-2-ol)} mixtures at 303.15 K

In view of industrial importance of binary {ethyl alcohol + (propan-1-ol/propan-2-ol)} mixtures, the densities (ρ) and refractive indices (n _D ) of these alkanols mixtures were measured for different compositions at 303.15 K. Molar volumes (V _m) and excess molar volumes (V ^E) of these binary mixtures were calculated from experimental density data of pure solvents and solvents mixtures. The measured refractive index and density data was used to calculate specific refractions (R _D ), molar refractions (R _M) and apparent molar refractions (R _{φ, i} ) of binary mixtures. From mole fraction dependence of apparent molar refractions, the limiting apparent molar refractions (R _{φ, i} ^○ ) of propan-1-ol and propan-2-ol have been determined. The graphical values of R _{φ, i} ^○ for propan-1-ol and propan-2-ol were found to be 9.5664 and 7.405 cm³ mol^?1 respectively. Structural changes, geometrical fittings and molecular interactions in binary mixtures of these alkanols have been discussed.     

Synthesis and structural characterisation of rhodium hydride complexes bearing N-heterocyclic carbene ligands

Addition of excesses of N-heterocyclic carbenes (NHCs) IEt₂Me₂, IⁱPr₂Me₂ or ICy (IEt₂Me₂ = 1,3-diethyl-4,5-dimethylimidazol-2-ylidene; IⁱPr₂Me₂ = 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene; ICy = 1,3-dicyclohexylimidazol-2-ylidene) to [HRh(PPh₃)₄] (1) affords an isomeric mixture of [HRh(NHC)(PPh₃)₂] (NHC = IEt₂Me₂ (cis-/trans-2), IⁱPr₂Me₂ (cis-/trans-3), ICy (cis-/trans-4) and [HRh(NHC)₂(PPh₃)] (IEt₂Me₂(cis-/trans-5), IⁱPr₂Me₂ (cis-/trans-6), ICy (cis-/trans-7)). Thermolysis of 1 with the aryl substituted NHC, 1,3-dimesityl-4,5-dihydroimidazol-2-ylidene (IMesH₂), affords the bridging hydrido phosphido dimer, [{(PPh₃)₂Rh}₂(μ-H)(μ-PPh₂)] (8), which is also the reaction product formed in the absence of carbene. When the rhodium precursor was changed from 1 to [HRh(CO)(PPh₃)₃] (9) and treated with either IMes (=1,3-dimesitylimidazol-2-ylidene) or ICy, the bis-NHC complexes trans-[HRh(CO)(IMes)₂] (10) and trans-[HRh(CO)(ICy)₂] (11) were formed. In contrast, the reaction of 9 with IⁱPr₂Me₂ gave [HRh(CO)(IⁱPr₂Me₂)₂] (cis-/trans-12) and the unusual unsymmetrical dimer, [(PPh₃)₂Rh(μ-CO)₂Rh(IⁱPr₂Me₂)₂] (13). The complexes trans-3, 8, 10 and 13 have been structurally characterised.     

H NMR and IR study of temperature-induced phase transition of negatively charged poly(N-isopropylmethacrylamide-co-sodium methacrylate) copolymers in aqueous solutions

¹H NMR and IR spectroscopies were used to investigate the temperature-induced phase transition behaviour of poly(N-isopropylmethacrylamide-co-sodium methacrylate) [P(IPMAAm/MNa)] copolymers, containing in aqueous solutions negatively charged MNa units (i = 1-10 mol%), and the obtained results were compared with those obtained for poly(N-isopropylmethacrylamide) (PIPMAAm) homopolymer. For PIPMAAm/H₂O solution, IR spectra indicate that the transition temperatures for the hydrophilic CO groups are slightly higher (by ∼ 2 K) in comparison with hydrophobic CH₃ groups. The decreasing values of phase-separated fraction p_max and the decrescent hysteresis during gradual heating and cooling, both with increasing content of MNa units i in the copolymer, show that for copolymers with i ? 5 mol% the globular-like structures formed at temperatures above the respective LCST are rather porous and disordered with relatively low degree of polymer-polymer hydrogen bonding. While for P(IPMAAm/MNa) copolymers with i ? 5 mol% most water molecules are expelled from globular structures, for i < 5 mol% a certain portion of water (HDO) molecules is rather tightly bound in globular structures; at the same time no releasing process was detected for the bound water even for 90 h.     

New effective reagent [Cp2ZrH2 · ClAlEt2]2 for alkene hydrometallation

New bimetallic complex [Cp₂ZrH₂ · ClAlEt₂]₂ (1) was synthesized, and its reactivity in hydrometallation reaction with the following alkenes was studied: hept-1-ene, okt-1-ene, α-methylstyrene, (1S)-β-pinene, (+)-camphene. Complex 1 shows the highest reactivity among the other known Al,Zr-bimetallic complexes: [Cp₂ZrH₂ · ClAlBuⁱ₂]₂ (2), [Cp₂ZrH₂ · AlEt₃]₂ (3), [Cp₂ZrH₂ · AlBuⁱ₃]₂ (4) and [Cp₂ZrH₂ · HAlBuⁱ₂] (5) as well as organoaluminium compounds (OAC): ⁱBu₂AlH, ⁱBu₃Al and ⁱBu₂AlCl in presence of Zr catalysts. Chlorine containing complexes 1 and 2 appear to be more effective in alkene hydrometallation, and relative hydrometallation rates are (1S)-β-pinene ? (+)-camphene < α-methylstyrene < oct-1-ene < hept-1-ene. Hydrometallation of (1S)-β-pinene and its subsequent oxidation with I₂ run with high diastereoselectivity and yield trans-myrtanol. However, the diastereoselectivity of (+)-camphene hydrometallation is less than that for (1S)-β-pinene, and the reaction gives predominately endo-camphanol.     

Synthesis of novel termetallic isopropoxides

Novel termetallic isopropoxides are reported which may be represented by the general formulae: [(PrⁱO)₃M(μ-OPrⁱ)₂Be(μ-OPrⁱ)₂Al(OPrⁱ)₂], [(PrⁱO)₂M(μ-OPrⁱ)₂Be(μ-OPrⁱ)₂Al(OPrⁱ)₂]₂ [where M = Ti(IV), Zr(IV) and Hf(IV)] and [(PrⁱO)₄M(μ-OPrⁱ)₂Be(μ-OPrⁱ)₂Al(OPrⁱ)₂] [where M = Nb(V) and Ta(V)]. Attempts to synthesize derivatives with the general formula, [(PrⁱO)₇M₂(μ-OPrⁱ)₂Be(μ-OPrⁱ)₂Al(OPrⁱ)₂] [where M = Ti(IV), Zr(IV) or Hf(IV)], were unsuccessful and in all such cases a mixture of M(OPrⁱ)₄ and [(PrⁱO)₃M(μ-OPrⁱ)₂Be(μ-OPrⁱ)₂Al(OPrⁱ)₂] was obtained. All these derivatives are soluble in common organic solvents and with the exception of titanium(IV) derivatives, they can be volatilised without noticeable disproportionation. These products have been characterized by elemental analyses, molecular weights, IR, ¹H NMR and (in representative cases) mass spectral studies also.     

Complexes of N-thiophosphorylthiourea (EtO)2P(O)CH2C6H4-4-[NHC(S)NHP(S)(OiPr)2] with Zn(II), Cd(II), Co(II) and Cu(PPh3)(I)

Reaction of O,O’-diisopropylthiophosphoric acid isothiocyanate (iPrO)₂P(S)NCS with diethyl 4-aminobenzylphosphonate (EtO)₂P(O)CH₂C₆H₄-4-NH₂ leads to the new N-thiophosphorylated thiourea (EtO)₂P(O)CH₂C₆H₄-4-[NHC(S)NHP(S)(OiPr)₂] (HL). Reaction of the potassium salt of HL with Zn(II), Cd(II) and Co(II) in aqueous EtOH leads to complexes of formula M(L-S,S’)₂ (ML₂). Heteroligand copper(I) complex of HL and triphenylphosphine was prepared by the reaction of the potassium salt KL and Cu(PPh₃)₃I. Copper in complex Cu(PPh₃)L is bound by one PPh₃ and one SCNPS fragment of the chelating ligand. Compounds obtained were investigated by IR, UV–Vis, ¹H and ³¹P{¹H} NMR spectroscopy, and microanalysis. The structures of HL and Cu(PPh₃)L were investigated by single crystal X-ray diffraction analysis.     

Ionic conductances in water-sulfolane mixtures at 30°C

Conductances of solutions of triisoamyl-n-butylammonium (iAm₃BuN⁺) iodide and sodium tetraphenylboride, iodide, and bromide have been measured in water-sulfolane mixtures at 30°C. Experimental data were analyzed by the 1965 Fuoss-Onsager-Skinner equations. The limiting equivalent conductances of triisoamyl-n-butylammonium tetraphenylboride (iAm₃BuNBPh₄) in each solvent mixture were obtained by the equation $$\Lambda _0 (iAm_3 BuNBPh_4 ) = \Lambda _0 ({\text{i}}Am_3 BuNI) + \Lambda _0 (NaBPh_4 ) - \Lambda _0 (NaI)$$ Limiting ionic equivalent conductances in water-sulfolane mixtures were calculated on the assumption thatι ₀(iAm ₃ BuNBPh ₄)/2λ₀(iAm ₃ BuN ⁺)=λ₀(BPh _- ⁴ ). The variations of the limiting ionic Walden product with solvent composition are discussed with respect to current information concerning solvent structural effects and ion-solvent interaction.     

Enantioselective aldol condensation of 1,3-bis-(trimethylsilyloxy)-1-methoxy-buta-1,3-diene promoted by chiral Ti(IV)/BINOL complex

Enantiomerically enriched δ-hydroxy-β-ketoesters are easily available by aldol condensation of 1,3-bis-(trimethylsilyloxy)-1-methoxy-buta-1,3-diene in the presence of Ti(O-iPr)₄/(S)-(−)-BINOL system. All reaction mixtures were separated by column chromatography and mostly isolated in moderate to good yields and all in high enantiomeric excesses.     

Molecular interactions in binary mixtures of non-electrolytes: Molar excess enthalpies

Molar excess enthalpies, H^E, for pyridine (i) + α-picoline (j), + β-picoline (j), + γ-picoline (j); pyridine (i) + cyclohexane (j); β-picoline (i) + cyclohexane (j); methylenebromide (i) + pyridine (j), + β-picoline (j) mixtures have been measured calorimetrically as a function of temperature and composition. The H^E data at 298.15 and 308.15 K have been analysed in terms of the Sanchez and Lacombe theory and the “graph theoretical approach”. The graph theoretical approach describes the H^E data well for all these mixtures. This approach has been critically examined and it is found to provide an insight into the nature of molecular interactions between the components of these mixtures. NMR studies on methylene bromide (i) + β-picoline (j) andβ-picoline (i) + pyridine (j) further support these conclusions.     

Synthesis of N-aryl-aza-crown ethers via Pd-catalyzed amination reactions of aryl chlorides with aza-crown ethers

The Pd₂(dba)₃/P(i-BuNCH₂CH₂)₃N (1) catalyst system effectively catalyzes the coupling of aza-crown ethers with electronically diverse aryl chlorides, affording N-aryl-aza-crown ethers in good yields. The Pd₂(dba)₃/P(i-BuNCH₂)₃CMe (2) catalyst system containing the more constrained bicyclic triaminophosphine is useful for aryl chlorides possessing base-sensitive ester, nitro, and nitrile functional groups.     

Palladium(II) complexes with S-benzyl dithiocarbazate and S-benzyl-N-isopropylidenedithiocarbazate: Synthesis,spectroscopic properties and X-ray crystal structures

Two new palladium(II) bis(NS) chelates, bis(S-benzyl dithiocarbazato)palladium(II) (1) and bis(S-benzyl-N-isopropylidenedithiocarbazato)palladium(II) (2), have been prepared and characterized using single-crystal X-ray diffraction and spectroscopic (electronic, IR and NMR) techniques. Complex 1 has a perfectly square planar trans configuration (point group C_i), while complex 2 has a distorted square planar cis configuration.     

Quantum-chemical calculation of spectral characteristics and structure of complexes [Mg(DMF) i (CH3CN)6−i ]2+ and IR spectra of the tricomponent solutions Mg(ClO4)2-DMF-CH3CN

Geometry of complexes [Mg(DMF) _i (CH₃CN)_6?i ]²⁺ (i from 0 to 6) was optimized, IR spectra were calculated, and values of ΔG of the ligand replacement in the cation coordination sphere were estimated by DFT BLYP/6-31G** method. Regularities in variations of spectral and structural characteristics of the complexes at variation in their compositions were elucidated. Quantitative relations between the calculated changes in frequency and intensity of the IR bands ν_C≡N, ν_C-C, ν_C=O, and δ_OCN of the complexes and the respective values in the IR spectra of solutions CH₃CN-Mg(ClO₄)₂-DMF at varying composition of the binary solvent were established. The main regularities in the changes of the DMF ν_C=O band contour in the process of resolvation of Mg²⁺ ions were interpreted.     

Synthesis of 1-fluoroindan-1-carboxylic acid (FICA) and its properties as a chiral derivatizing agent

1-Fluoroindan-1-carboxylic acid (FICA) (1) was designed and synthesized as its methyl ester (FICA Me ester) (4) in order to develop an efficient chiral derivatizing agent (CDA) which excels α-methoxy-α-(trifluoromethyl)phenylacetic acid (MTPA) in capability. FICA Me ester (4) was prepared by fluorination of methyl 1-hydroxyindan-1-carboxylate (3) with (diethylamino)sulfur trifluoride (DAST) and derived to the esters of racemic secondary alcohols by ester exchange reaction. The resulting Δδ_F value was large in the case of 2-butyl ester of FICA (5a), whereas not detectable in the case of the corresponding MTPA ester (6a). The magnitude of the Δδ_H values was similar to that of MTPA esters. The diastereomers of (R)-(−)-8-phenylmenthyl ester of FICA (5i) was separated and their ¹H NMR analyses revealed that the concept of the modified Mosher's method was successfully applied to 5i.     

Pd2dba3/P(i-BuNCH2CH2)3N: a highly efficient catalyst for the one-pot synthesis of trans-4-N,N-diarylaminostilbenes and N,N-diarylaminostyrenes

A Pd₂dba₃/P(i-BuNCH₂CH₂)₃N catalyzed one-pot synthesis of unsymmetrically substituted trans-4-N,N-diarylaminostilbenes and both symmetrically and unsymmetrically substituted N,N-diarylaminostyrene derivatives is reported. The procedure involves two or more palladium catalyzed sequential coupling reactions (an amination and an inter-molecular Heck reaction) in one-pot using the same catalyst system with two different aryl halides, including aryl chlorides and hetero aryl halides as the coupling partners.     

IR spectra of aqueous disperse systems adsorbed atmospheric gases: 1. Nitrogen

Spectral characteristics of (H₂O) _i , N₂(H₂O) _i , and (N₂)₂(H₂O) _i cluster systems, where 10≤i≤50, are studied in the 0 ≤ ε ≤ 3500 cm^?1 frequency range with the molecular dynamics method on the basis of a flexible molecule model. After nitrogen is captured by an aqueous disperse system, the absorption of the IR radiation by this system increases owing to the enhancement of intramolecular vibrations. In general, the reflection of the outer IR radiation by nitrated aqueous disperse systems is attenuated; however, when the nitrogen concentration increases twofold, there is a tendency toward an increase in the fraction of reflected radiation. As the nitrogen concentration in a system of water clusters rises, the power of radiation emitted by the system increases significantly and the number of electrons interacting with the outer IR radiation decreases.