Excess molar volumes of binary mixtures of 2,2,2-trifluoroethanol with water,or acetone,or 1,4-difluorobenzene,or 4-fluorotoluene,or α,α,α, trifluorotoluene or 1-alcohols at a temperature of 298.15 K and pressure of 101 kPa

Excess molar volumes V_m^E of binary mixtures of 2,2,2-trifluoroethanol with water, or acetone, or methanol, or ethanol, or 1-alcholos, or 1,4-difluorobenzene, or 4-fluorotoluene or α,α,α-trifluorotoluene were measured in a vibrating tube densimeter at temperature 298.15 K and pressure of 101 kPa. The V_m^E extrema are: 1.540 cm³ · mol⁻¹ for (2,2,2-trifluoroethanol + 1-heptanol); 1.452 cm³ · mol⁻¹ for (2,2,2-trifluoroethanol + 1-hexanol); 1.238 cm³ · mol⁻¹ for (2,2,2-trifluoroethanol + 1-butanol); 0.821 cm³ · mol⁻¹ for (2,2,2-trifluoroethanol + 4-fluorotoluene); 0.817 cm³ · mol⁻¹ for (2,2,2-trifluoroethanol + ethanol); 0.647 cm³ · mol⁻¹ for (2,2,2-trifluoroethanol + methanol); 0.618 cm³ · mol⁻¹ for (2,2,2-trifluoroethanol + acetone); 0.605 cm³ · mol⁻¹ for (2,2,2-trifluoroethanol + α,α,α-trifluorotoluene); 0.485 cm³ · mol⁻¹ for (2,2,2-trifluoroethanol + 1,4-difluorobenzene); and −0.656 cm³ · mol⁻¹ for (2,2,2-trifluoroethanol + water). The limiting excess partial molar volumes are estimated.     

Three-Component Reaction of β-Ketosulfone,Formaldehyde, and Thiol or Thiophenol in Water

Abstract

A three-component reaction of β-ketosulfone, formaldehyde, and thiol or thiophenol was developed. The reaction was performed in pure water under a catalyst-free condition, and the corresponding Mannich-type thioethers were obtained in good to excellent yields. Finally, a one-pot stepwise four-component reaction of sodium benzenesulfinate, α-bromoketone, β-ketosulfone, and thiophenol was also developed.     

Luminescence Properties of Terbium-, Cerium-, or Europium-Doped α-Sialon Materials

New interesting luminescent α-sialon (M_(m/val+)^val+ Si_12-(m+n) Al_(m+n)OnN_(16−n)) (M=Ca, Y) materials doped with Ce, Tb, or Eu have been prepared and their luminescence properties studied. These show that Tb and Ce are in the 3+ and Eu in the 2+ state. Low-energy 4f↔5d transitions are observed as compared to the luminescence of these ions doped in oxidic host-lattices. This is partially explained by the nitrogen-rich coordination of the rare-earth ion and partially by the narrow size of the lattice site. The latter gives rise to a strong crystal-field splitting of the 5d band and a rather large Stokes shift for Ce³⁺ and Eu²⁺ (6500-7500 and 7000-8000 cm⁻¹, respectively). For (Y,Tb)-α-sialon the Tb³⁺ 4f→5d excitation band (∼260 nm) is in the low-energy host-lattice absorption band (?290 nm), giving rise to a strong absorption for 254-nm excitation, but a low quantum efficiency. The latter is due to photoionization processes or selective excitation of Tb³⁺ at the defect-rich surface, resulting in radiationless transitions. Ce- and Eu-doped Ca-α-sialon show bright long-wavelength luminescence (maxima at 515-540 and 560-580 nm for Ce and Eu, respectively) with a high quantum efficiency and high absorption for 365- and 254-nm excitation. The Eu²⁺ emission intensity and absorption increases for increasing m, which is explained by the Eu²⁺ richer α-sialon composition. The position of the Eu^2α emission does not shift with changing composition of the host-lattice (m, n values), indicating that the local coordination of the Eu²⁺ ion is hardly dependent on the matrix composition.     

Synthesis of 3 or 4-Substituted Pyridine-2, 6-Dicarboxylic Acid

Time-resolvedcircularlypolarizedluminescence(CPL)studieshavebeenparticularlysuccessfulatmeasuringdifferencesinquenchingrateconstantsincertaindiastereomericdonor-acceptorsystems'ItisanticipatedthatthesetypesofexperimentsmaybeappliedtomorecomplexsystemsinvolvingracemiclanthanideemittercomplexesinasolutioncontainingtransitionmetalcomplexesenantioselectivelyboundtoDNA2.However,theluminophoreswereonlyconfinedtoLn(DPA),'-andLn(CDA),'(Ln=Eu' ,Tb' ,DPA=dipicolinatedianion,CDA=chelidamate).Eff…     

Three-Component Reaction of Triphenylphosphine,Acetylenic Esters,and 6-Aminouracil or 6-Amino-N,N′-dimethyluracil

Protonation of the reactive 1:1 intermediate produced in the reaction of acetylenic esters and triphenylphosphine by 6-aminouracil or 6-amino-N,N′-dimethyluracil leads to vinylphosphonium salts, which undergo Michael addition with the conjugate base of the NH acid to produce highly fanctionalized, salt-free phosphorus ylides in excellent yields.     

Phase diagrams of (vapour + liquid) equilibrium for binary mixtures of α,α,α-trifluorotoluene with ethanol,or benzene,or chloroform at pressure 101.4 kPa

(Vapour + liquid) equilibrium (VLE) of binary mixtures of (ethanol + α,α,α-trifluorotoluene), (benzene + α,α,α-trifluorotoluene), and (chloroform + α,α,α-trifluorotoluene) have been investigated at the pressure 101.4 kPa using the dynamic-ebulliometry method over the whole composition range. The correlated VLE phase diagrams were adequately described by means of NRTL and UNIQUAC thermodynamic models. Fair attractive energies in the first two systems are capable to yield azeotropes, while moderate repulsive energies in the later system make it zeotrope.     

Viscosities and Densities of Solutions of n-Decane, or n-Tetradecane with Several Esters at 25°C

Viscosity and density data are reported for n-decane + propyl ethanoate, propyl propanoate, propyl butyrate, and n-tetradecane + propyl ethanoate, propyl propanoate, and propyl butyrate at 25°C and atmospheric pressure. Kinematic viscosities were determined using a capillary viscosimeter and densities were measured using vibrating-tube densimetry. The equations of Grunberg–Nissan, McAllister, Auslander, and Teja were fitted to the viscosity data. Excess molar Gibbs free energies of activation for flow were also evaluated. The experimental values obtained for excess volumes were compared with the Nitta et al. group contribution model.     

Nearly Degenerate Isomers of C(BH)2: Cumulene,Carbene, or Carbone?

The ground electronic state of C(BH)₂ exhibits both a linear minimum and a peculiar angle‐deformation isomer with a central B‐C‐B angle near 90°. Definitive computations on these species and the intervening transition state have been executed by means of coupled‐cluster theory including single and double excitations (CCSD), perturbative triples (CCSD(T)), and full triples with perturbative quadruples (CCSDT(Q)), in concert with series of correlation‐consistent basis sets (cc‐pVXZ, X=D, T, Q, 5, 6; cc‐pCVXZ, X=T, Q). Final energies were pinpointed by focal‐point analyses (FPA) targeting the complete basis‐set limit of CCSDT(Q) theory with auxiliary core correlation, relativistic, and non‐Born–Oppenheimer corrections. Isomerization of the linear species to the bent form has a minuscule FPA reaction energy of 0.02 kcal mol^?1 and a corresponding barrier of only 1.89 kcal mol^?1. Quantum tunneling computations reveal interconversion of the two isomers on a timescale much less than 1 s even at 0 K. Highly accurate CCSD(T)/cc‐pVTZ and composite c～CCSDT(Q)/cc‐pCVQZ anharmonic vibrational frequencies confirm matrix‐isolation infrared bands previously assigned to linear C(BH)₂ and provide excellent predictions for the heretofore unobserved bent isomer. Chemical bonding in the C(BH)₂ species was exhaustively investigated by the atoms‐in‐molecules (AIM) approach, molecular orbital plots, various population analyses, local mode vibrations and force constants, unified reaction valley analysis (URVA), and other methods. Linear C(BH)₂ is a cumulene, whereas bent C(BH)₂ is best characterized as a carbene with little carbone character. Weak B–B attraction is clearly present in the unusual bent isomer, but its strength is insufficient to form a CB₂ ring with a genuine boron–boron bond and attendant AIM bond path.     

Phase equilibria of binary mixtures containing methyl acetate,water, methanol or ethanol at 101.3 kPa

Isobaric vapor–liquid equilibria data at 101.3?kPa were reported for the binary mixtures (methyl acetate?+?(water or methanol or ethanol), methanol?+?(water or ethanol) and (ethanol?+?water)). The experimental data were tested for thermodynamic consistency by means of the Wisniak method and were demonstrated to be consistent. The experimental data were correlated using Wilson, NRTL and UNIQUAC models for the activity coefficients and predicted using the UNIFAC and PSRK equation of state for testing theirs capability. The results show that the obtained data for the studied binary systems are more reliable than other published data.     

Viscometric and volumetric properties of benzene + methyl acetate,or + methyl propanoate,or + methyl butanoate binary systems at 283.15, 298.15 and 313.15 K

Viscosities and densities of three binary liquid mixtures, benzene?+?methyl acetate, benzene?+?methyl propanoate and benzene?+?methyl butanoate, have been measured at 283.15, 298.15 and 313.15?K, and atmospheric pressure. From experimental data, viscosity deviation, excess energy of activation for viscous flow, and excess molar volume were calculated and satisfactorily correlated with Redlich and Kister equation. Empirical and semiempirical equations and the predicted group-contribution method, universal automatic computer, were applied.     

Inside or outside a ligand cleft? Synthetic, structural, and kinetic inertness studies of zinc, cadmium, and mercury complexes of cross-bridged cyclam and cyclen

Ethylene cross-bridging of the popular tetraazamacrocyclic ligand cyclam has led to metal complexes with enhanced kinetic inertness. The synthesis and spectral characterization of zinc(II), cadmium(II), and mercury(II) complexes of cross-bridged cyclam (L1) as well as cross-bridged cyclen (L2) are reported along with the details of our synthetic route to L2. X-ray structural studies revealed that all Zn(II) and Cd(II) cations are fully kappa(4)N-coordinated inside the respective ligand's molecular cleft with L1 providing the better fit for Zn(II). While Hg(II) is similarly coordinated to L2, it has been found to complex L1 outside the ligand cleft in a novel exo-kappa(2)N-mode. Solution NMR data of the kappa(4)N complexes are consistent with the presence of only a single cis-folded isomer in each case. Ligand (1)H and (13)C coupling to both (111,113)Cd and (199)Hg in their complexes can be clearly discerned. The relative kinetic inertness of representative cross-bridged complexes in acidic aqueous solution has been assessed and found to be in the following order: Zn(II) > Cd(II)[dbl greater-than] Hg(II). The data also reaffirm that cross-bridged cyclam ligand L1 forms a substantially more inert complex with zinc(II) than either the smaller cyclen analogue L2 or the unbridged 1,4,8,11-tetramethyl-cyclam L3.     

Reactivity of allylic and vinylic silanes,germanes, stannanes and plumbanes toward SH2′ or SH2 substitution by carbon- or heteroatom-centered free radicals

Compounds of the type CH₂CHCH₂MR₃ and E-PhCHCHMR₃ (M  Si, Ge, Sn, Pb) were allowed to react with a series of heteroatom-centered radicals (PhY ·, Y = S, Se, Te, derived from PhYYPh) and carbon-centered radicals ((CH₃)₂CH · derived from (CH₃)₂CHHgCl). We report that alkenylplumbanes and, under forcing conditions, alkenylgermanes undergo S_H2 or S_H2′ substitution of the metal by chain mechanism analogous to those previously reported for alkenylstannanes. Alkenylsilanes are unreactive.Based solely upon product yields, the following trends were observed: The reactivity of the alkenylmetals follow the order metal = Pb > Sn > Ge (> Si). The allylmetals were more reactive then the β- metallostyrenes toward the reactants employed in this study. The chalcogen series PhYYPh exhibits the reactivity order Y = S > Se > Te.     

Peptide analysis of tooth enamel – A sex estimation tool for archaeological,anthropological, or forensic research

Proteomics has become an attractive method to study human and animal material, biological profile, and origin as an alternative to DNA analysis. It is limited by DNA amplification in ancient samples and its contamination, high cost, and limited preservation of nuclear DNA. Currently, three approaches are available to estimate sex–osteology, genomics, or proteomics, but little is known about the relative reliability of these methods in applied settings. Proteomics provides a new, seemingly simple, and relatively non-expensive way of sex estimation without the risk of contamination. Proteins can be preserved in hard teeth tissue (enamel) for tens of thousands of years. It uses two sexually distinct forms of the protein amelogenin in tooth enamel detectable by liquid chromatography-mass spectrometry; the protein amelogenin Y isoform is present in enamel dental tissue only in males, while amelogenin isoform X can be found in both sexes. From the point of view of archaeological, anthropological, and forensic research and applications, the reduced destruction of the methods used is essential, as well as the minimum requirements for sample size.     

Nature of "hydrogen bond" in the diborane-benzene complex: covalent, electrostatic, or dispersive?

Motivated by the recent discovery of unusual "hydrogen bonding"-like interaction between a borane system and benzene molecules in a molecular crystal, we carried out quantum mechanical calculations on a model complex, diborane-benzene cluster. The aim is to understand the nature of this unique interaction, which is expected to play an essential role in this novel class of molecular crystals. As analyzed in the present study, the interaction between diborane and benzene is special in the following aspects: (1) this interaction is mostly dispersive; (2) the observed pseudodirectionality with one of the diborane bridge hydrogen directed toward the benzene centroid minimizes the van der Waals contact; and (3) in the "hydrogen bond" map, this interaction is located in a unique region, which is presently populated by a few known molecular complexes with very different chemical characteristics. It is anticipated that the results from the present analysis will provide meaningful guidance for molecular engineering with diborane-benzene as a building block and for stabilization of this and possible other hydrogen bonds by dispersive contributions.     

High-resolution ICP–MS determination of Ti,V, Cr,Co, Ni,and Mo in human blood and urine of patients implanted with a hip or knee prosthesis

The main components (Ti, V, Cr, Co, Ni, and Mo) of metallic alloys currently used in hip and knee articular prostheses have been simultaneously determined in human whole blood and urine of implanted people by a (HR)-ICP–MS method previously developed in our laboratory. The determination of those elements has been carried out in patients with knee and hip prosthesis and in a group of pre-operation patients without any metallic device in their bodies, used as controls, demonstrating the usefulness of this technique to perform multielement analysis at ppt levels in complex matrices. The concentrations of V, Cr, Co, Ni, and Mo in urine and blood of implanted people turned out to be very similar to those obtained in control patients. However, raised Ti levels could be found both in urine and blood of patients with articular prostheses made or coated with a titanium alloy (Ti₆Al₄V).     

Atom Transfer Radical Polymerization of Methyl Methacrylate with α,α-Dichlorotoluene or α,α,α-Trichlorotoluene as Initiator

lnAtomTransferRadicalPolymerization(ATRP),whichisanew"living"/contr0lledradicalp0lymerizati0ntechniquedevel0pedindependentlybyMatyjaszewskieIallandSawam0t0eIaP,anyalkyIhalidewithactivatedsubstituents0na-carbonsuchasaryl,carb0nyl0rallylcanbeusedasinitiatoe.Benzy1haIideandpolymerswithbenzylhalideendgr0upwerereportedtobeefficientinitiator0rmacroinitiatorfortheATRPofstyrene".H0wever,whenbenzylhalidewasusedt0initiateMMAp0Iymerization,itwasfoundthattheinitiationefficiencywasveryIowinourlabo…     

Chemistry-structure-simulation or chemistry-simulation-structure sequences? The case of MIL-34, a new porous aluminophosphate

A new aluminophosphate, MIL-34, is investigated from its as-synthesized structure to its calcined microporous form. Single-crystal X-ray diffraction measurements on the as-synthesized MIL-34 (Al(4)(PO(4))(4)OH x C(4)H(10)N, space group P-1, a = 8.701(3) A, b = 9.210(3) A, c = 12.385(3) A, alpha = 111.11(2) degrees, beta = 101.42(2) degrees, gamma = 102.08(2) degrees, V = 863.8(4) A(3), Z = 2, R = 3.8%) reveal a 3-D open framework where Al atoms are in both tetrahedral and trigonal bipyramidal coordinations. It contains a 2-D pore system defined by eight rings where channels along [100] cross channels running along [010] and [110]. CBuA molecules are trapped at their intersection. (27)Al, (31)P, and (1)H MAS NMR spectroscopies corroborate these structural features. Calcination treatments of a powder sample of the as-synthesized MIL-34 indicate its transformation into the related template-free structure that is stable up to 1000 degrees C. Lattice energy minimizations are then used in order to anticipate the crystal structure of the calcined MIL-34, starting with the knowledge of the as-synthesized structure exclusively. Energy minimizations predict a new regular zeotype structure (AlPO(4), space group P-1, a = 8.706 A, b = 8.749 A, c = 12.768 A, alpha = 111.17 degrees, beta = 97.70 degrees, gamma = 105.14 degrees, V = 846.75 A(3), Z = 2) together with a thermodynamic stability similar to that of existing zeotype AlPOs. Excellent agreement is observed between the diffraction pattern calculated from the predicted calcined MIL-34 and the experimental X-ray powder diffraction pattern of the calcined sample. Finally, the atomic coordinates and cell parameters of the calcined MIL-34 predicted from the simulations are used to perform the Rietveld refinement of the calcined sample powder pattern, further corroborated by (27)Al and (31)P NMR measurements. This unique combination of experiment and simulation approaches is an interesting and innovative strategy in materials sciences, where simulations articulate the prediction of a possible template-free framework from its as-synthesized templated form. This is especially valuable when straightforward characterizations of the solid of interest with conventional techniques are not easy to carry out.     

Hafnium Chloride Catalyzed Polycondensation of α,ω-Alkanediol with Dicarboxylic Acids or Succinic Anhydride

Three different kinds of polycondensation were preformed and the usefulness of HfCl₄.2THF as estrification and polycondensation catalyst was evaluated. It was compared with HfCl₄, BiCl₃, LaCl₃ and SnCl₂. In polycondensations of 1,6-hexandiol, and 1,10-decandiol with various dicarboxylic acids all catalysts failed to give satisfactory results. However, in polycondensations of 1,4-butanediol with succinic anhydride in refluxing decalin good results were obtained, and HfCl₄.2THF was the most effective catalyst after SnCl₂. The MALDI-TOF mass spectra revealed that cyclization made a significant contribution to the limitation of the chain growth.     

Investigations of the Chemistry of Alkyl Phosphites Toward Nitrogen-Containing Compounds: Efficient Approaches to α-Amino-, β-Amino-, and/or Enaminophosphonates

Abstract

In this study, we report recent investigations of the chemical reactivity of alkyl phosphites, mainly trialkyl and dialkyl phosphites, with molecules containing different nitrogen-containing compounds reported by us and other research groups over the past 25 years. Previous ground-breaking important reports are also considered. The reviewed investigations in this article are grouped according to only the type of the nitrogen-functional groups [amines (primary, secondary, and tertiary amines), imines, amides, thioamides, nitriles, isocyanates, isothiocyanates, oximes, hydrazones, diazo, and azides] and not according to the site of attack or the final products. Furthermore, the present review article focuses on the synthesis of α-amino-, β-amino-, and/or enaminophosphonates. These compounds have important roles in pharmaceutical chemistry.