Localization of Hydrogen and Content of Oxonium Cations in Alunite via Neutron Diffraction

Polycrystalline alunite‐d₆ KAl₃(OD)₆(SO₄)₂, prepared by hydrothermal reaction of Al₂(SO₄)₃, K₂SO₄ and D₂SO₄, was studied by neutron powder diffraction performed on the diffractometer E2 (HMI‐BENSC, Berlin). Rietveld refinement of the data set for T = 2 K yielded the crystallographic data: space group R3m, Z = 3, trigonal setting, a = 694.3(1) pm, c = 1722.7(2) pm, N(I/σ(I) > 1) = 172, N(Var.) = 19, R_p = 0.036, wR_p = 0.046, R_B(I/σ(I) > 1) = 0.020. The deuterium nuclei could be located precisely. Three equivalent O–D bonds with nuclear distances r(O(4)–D) = 96.6(3) pm directed to each of the terminal oxygen atoms of the SO₄ groups are found. Partial substitution of K⁺ by D₃O⁺ was also considered in the refinement procedure. In good agreement with results of other methods a site occupation fraction n(D₃O⁺) = 0.0104 was obtained.     

Synthesis, X-ray diffraction study, and ionic conductivity of new AB2O6 pyrochlores

The oxides A(Ti_0.5Te_1.5)O₆ (A = K, Rb, Cs, Tl), A(Ti_0.5W_1.5)O₆ (A = Rb, Cs, Tl), and Cs(B_0.5W_1.5)O₆ (B = Zr, Hf) have been obtained as polycrystalline powders giving X-ray diffraction patterns characteristic of defect cubic pyrochlores, space group (No. 227), Z = 8. The best discrepancy R factors, from 0.0265 for Rb(Ti_0.5Te_1.5)O₆ to 0.0554 for Cs(Zr_0.5W_1.5)O₆, were obtained for the B cations randomly distributed at 16(d), A ions at one quarter of 32(e), and oxygen atoms at 48(f) positions. A linear relationship is observed between the a unit cell parameters and the ionic radii of the A cations, as well as the average ionic radii of the B atoms. The results of electrical resistivity measurements for A(Ti_0.5Te_1.5)O₆ (A = K, Rb, Cs, Tl) are given.     

Frontier orbital interactions of electron pushing and drawing substituents with ferrocenyl group

The frontier orbital interactions of electron pushing and drawing substituents with ferrocenyl group were analyzed based on the electrochemical,UV visible spectral and spectroelectrochemical results of five ferrocene derivatives,R-Fc-A1(PⅠ),A1-Fc-A1(PⅡ),D-Fc-R (PⅢ),D-Kc-A1(PIV) and D-Fc-A2(PV)(R,CH2OH;A1 CHO;A2,CH=C(CN)2 and D,(C18H37)2N-C6H4-CH=CH) It was found that there are strong interactions of the LUMO (πA) of electron drawing substituents with le2g(dxy,dx2 y2)and e2u of the ferroeenyl group because the energy levels of πA and e2g,C2U of (Cp )2 are close,which lower not only the energy levels of bonded orbits,πA+ and dx2-y2+[πA] of PⅠ,PⅡ,PⅣ and PⅤobviously,but also those of their non-bonded orbu dxy For PⅢ,PⅣ and PⅤ,there are strong interactions of HOMO(πD) of the electron pushing substituent with le of the ferrocenyl group because the levels of πD and e of (Cp)2 are close,which result in the formation of anti-bonded orbit,πD- and bonded orbit     

Pyrolysis of 2-phenylethylamines heats of formation of aminomethyl radicals R2NCH2 · (R = H,CH3)

A kinetic study of the very low-pressure pyrolysis of ethylbenzene (I), 2-phenylethylamine (II), and N,N-dimethyl 2-phenylethylamine (III) above 900 K yields the heats of formation of aminomethyl (A) and N,N-dimethylaminomethyl (B) radicals: ΔH_{?, 300 K}(A) = 30.3 and ΔH_{?, 300 K}(B) = 27.5 kcal/mol. The difference of stabilization energies E_s, (relative to methyl radicals): Δ = E_s(B) ? E_s(A) = (2 ± 1) kcal/mol, conforms to similar effects in methyl substituted alkyl and amino free radicals.     

Preparation of complexes formed in the reaction between diironnanocarbonyl and tetraalkyl(phenyl)diphosphine disulfides,R2P(S)P(S)R2 (R=Et,n -Pr,n -Bu,Ph)

Fe₂(CO)₉ and R₂P(S)P(S)R₂ (R = Et, n-Pr, n-Bu, Ph) react to form two types of cluster complexes Fe₃(CO)₉(μ₃-S)₂ (1), Fe₂(CO)₆(μ-SPR₂)₂ (2A)–(2D), [2A, R = Et; 2B, R = n-Pr; 2C, R = n-Bu; 2D, R = Ph]. The complexes result from phosphorus–phosphorus bond scission; in the former sulfur abstraction has also occurred. The complexes have been characterized by elemental analyses, FT-IR and ³¹P-[¹H]-NMR spectroscopy and mass spectrometry.     

用对称透射二维WAXS强度研究PET取向非晶态结构

用对称透射法，测试聚酯（ＰＥＴ）取向非晶试样的二维广角Ｘ射线散射相干强度Ｉ（Ｋ，α），将不同方位角α上的Ｉ（Ｋ，α）非晶重叠峰曲线进行计算分解，获得分子链间原子散射引起的二个峰为Ａ（Ｋ＝０．１２６），Ｂ（Ｋ＝０．１６９），分子链内原子散射引起五个峰分别为Ｃ（Ｋ＝０．３０４），Ｄ（Ｋ＝０．５５３），Ｅ（Ｋ＝０．３７４），Ｆ（Ｋ＝０．４６５），Ｇ（Ｋ＝０．６０６），Ｋ单位为ｎｍ＾－１，分析了它们的结构     

Synthesis of Novel Chiral C 2-symmetric Diaza-18-crown-6 Ether Derivatives and their Enantioselective Recognition of Amino Acid Derivatives

New chiral diaza-18-crown-6 ether derivatives, 5 and 6 were synthesized from (R)-(-)-2-amino-1-bütanol. These chiral artificial receptors exhibit pronounced chiral recognition toward the enantiomers of l- and d- amino acid derivatives. The highest enantioselectivity was observed in the case of Trp-OMe·HCl (K_D/K_L=12.5).     

Photon correlation spectroscopy of polystyrene as a function of temperature and pressure

Photon correlation spectroscopy is employed to study the slowly relaxing density and anisotropy fluctuations in bulk atactic polystyrene as a function of temperature from 100 to 160°C and pressure from 1 to 1330 bar. The light-scattering relaxation function is well described by the empirical function ?(t) = exp[?(t/τ)^β], where for polystyrene β = 0.34. The average relaxation time is determined at each temperature and pressure according to 〈τ〉 = (τ/β)Γ(1/β) where Γ(x) is the gamma function. The data can be described by the empirical relation 〈τ〉 = 〈τ〉₀ exp[(A + BP)/R(T ? T₀)] where R is the gas constant and T₀ is the ideal glass transition temperature. The empirical constant A/R is in good agreement with that determined from the viscosity or the dielectric relaxation data (1934 K). The empirical constant B can be interpreted as the activation volume for the fundamental unit involved in the relaxation and is found to be comparable to one styrene subunit (100 mL/mol). The quantity B appears to be a weak function of temperature. The use of pressure as a tool in the study of light scattering near the glass transition now has been established.     

Zur Darstellung unsymmetrisch substituierter Bis(organylamino) silane

The title compoundsR ₂Si(NHR ¹) (NHR ²) (B) were prepared according to Equ. (2) and (3) and via formerly unknown diphenyl-chloro-organylaminosilanes (A) as intermediates. The complex course of formation ofB in competition withR ₂Si (NHR ¹)₂ (C) andR ₂Si(NHR ²)₂ (D) (Scheme 1, Equ. (4)–(7), Table 2) was investigated in detail. Results of thermal rearrangement ofB are given in Table 5. Five novelA and six novelB compounds are confirmed by properties, elemental and structural data (Tables 1, 3 and 4).

Mit Auszügen aus der DissertationS. Klemke, Techn. Univ. Braunschweig 1978.     

New details in the polarized spectrum of naphthalene by means of linear dichroism studies in oriented polymer matrices

Linear dichroism (LD) spectra are presented for naphthalene oriented in stretched polyethylene and polypropylene matrices at 77 K and 296 K. From the calculated spectrum LD(λ)/A(λ), where A(λ) is the corrected absorbance spectrum of the sample by unpolarized light, orientational parameters are calculated and component spectra, 235–315 nm, are resolved corresponding to polarization parallel to the long (B_3u = x) and the short (B_2u = y) axes in the molecular plane (D_2h). The orientational parameters indicate different orientational mechanisms in polyethylene and polypropylene, but the resolving procedure yields mainly identical component spectra. It is suggested that the polarization (B_3u) predominating in the 245–275 nm region isdue to a B_1g vibronic perturbation of the ¹B_2u state.     

Equilibrium structure and vibrational frequencies of the O4 molecule

SCF closed shell calculations were performed to determine the equilibrium structure and vibrational frequencies of the O₄ molecule by means of Payne's method and with the help of the molecule's symmetry coordinates. The equilibrium geometry corresponds to symmetry group D_2d with R = 1.505 Å and h = 0.094 Å. The vibrational frequencies are: ν₅(E) = 885.5 cm^?1, ν₃(B₁) = 1051.9 cm^?1, ν₁(A₁) = 1018.3 cm^?1, ν₄(B₂) = 880.3 cm^?1. The second vibrational coordinate (A₁) corresponds to a double-well potential. The first vibrational levels were calculated by a variational method.     

Impact of high pyruvate concentration on kinetics of rabbit muscle lactate dehydrogenase

In order to evaluate the effectiveness of l-lactate dehydrogenase (LDH) from rabbit muscle as a regenerative catalyst of the biologically important cofactor nicotinamide adenine dinucleotide (NAD), the kinetics over broad concentrations were studied to develop a suitable kinetic rate expression. Despite robust literature describing the intricate complexations, the mammalian rabbit muscle LDH lacks a quantitative kinetic rate expression accounting for simultaneous inhibition parameters, specifically at high pyruvate concentrations. Product inhibition by l-lactate was observed to reduce activity at concentrations greater than 25 mM, while expected substrate inhibition by pyruvate was significant above 4.3 mM concentration. The combined effect of ternary and binary complexes of pyruvate and the coenzymes led to experimental rates as little as a third of expected activity. The convenience of the statistical software package JMP allowed for effective determination of experimental kinetic constants and simplification to a suitable rate expression:

Estimated ionicB-coefficients from NMR measurements in aqueous electrolyte solutions

¹⁷O-NMR spin-lattice relaxation timesT ₁ of D₂O molecules were measured at 5–85°C in D₂O solutions of alkali metal halides (LiClCsCl, KBr, and KI), DCl, KOD, Ph₄PCl, NaPh₄B, and tetraalkylammonium bromides (Me₄NBrAm₄NBr) in the concentration range 0.1–1.4 mol-kg^–1 TheB-coefficients of the electrolytes obtained from the concentration dependence of relaxation ratesR ₁=1/T₁ were divided into the ionicB-coefficients by three methods: (i) the assumption ofB (K⁺)=B(Cl^–), (ii) the assumption ofB(Ph₄P⁺)=B(Ph₄B^–), and (iii) the use ofB(Br^–) obtained from a series ofB(R₄NBr). It was found that Methods (ii) and (iii) resulted in an abnormal temperature dependence of theB-coefficients of alkali metal ions and a negative values of rotational correlation times _c at lower temperatures for hydroxide and halide ions. These results suggest that the methods based on the van der Waals volume are not adequate for the ionic separation of NMRB-coefficients. From the analysis using the assumption ofB(K⁺)=B(Cl^–), it was found that D₃O⁺, OD^–, and Me₄N⁺ ions are the intermediates between structure makers and breakers, and that the hydrophobicity of phenyl groups is weaker than that of alkyl groups due to the interactions between water molecules and -electrons in phenyl groups.     

Hydrogen bonding abilities and self-association of thiazolidin-and imidazolidin-2-ones and 2-selenones

The hydrogen bonding abilities of iV-methylimidazolidin-2-one and -2-selone and thiazolidin-2-one and -2-selenone have been studied by ir spectroscopy at 25° in carbon tetrachloride solutions, using dimethyl sulphoxide and 4-chlorophenol as proton acceptor (K_A) and proton donor (K_B), respectively. The results are compared with those previously reported for N-methylimidazolidine-2-thione and thiazolidine-2-thione. The K_A values increase in each series in the order O < S < Se and Kg in the reverse order. The and K_B values are discussed in terms of the substituent in ring. The self-association constants (K_D) are dependent on both K_A and K_B, although K_A seems to be much more important.     

Theory of dynamic light scattering by polymers and gels

It is shown under very general conditions that the intermediate scattering function for the generalized Rouse—Zimm model always takes the simple form G(K, t) α exp[?K²(k_BT/f)t], when the scattering vector K becomes sufficiently large. (Here k_B is Boltzmann's constant, T is the absolute temperature and f is the individual bead friction factor.) A microscopic formulation for the bulk modulus and friction factor density of a gel network is incorporated into the viscoelastic continuum model of Tanaka et al. The resulting expression for the apparent long-wavelength diffusion coefficient of the gel is D_G = (k_BT/f)2(1 - 2/Φ), where Φ is the network functionality.     

Mixed Alkali Neodymium Orthoborates: K9Li3Nd3(BO3)7 and A2LiNd(BO3)2 (A = Rb,Cs)

Crystals of mixed alkali neodymium orthoborates, K₉Li₃Nd₃(BO₃)₇ and A₂LiNd(BO₃)₂ (A = Rb, Cs) were obtained by spontaneous crystallization. K₉Li₃Nd₃(BO₃)₇ crystallizes in space group P2/c with cell parameters of a = 11.4524(7) Å, b = 10.1266(6) Å, c = 12.3116 (10) Å, β = 122.0090(10)°. In the structure, NdO₈ polyhedra share corners and connect with planer BO₃ groups to form infinite [Nd₃B₃O₂₁]_n chains. These chains are linked by additional BO₃ groups to produce a double layer of [Nd₆B₆O₃₈]_n blocks in the ac plane with K and Li ions filled into the cavities. A₂LiNd(BO₃)₂ (A = Rb, Cs) crystallizes in space group Pbcm, with cell parameters of a = 7.113(2) Å, b = 9.691(3) Å and c = 10.135(3) Å for Rb₂LiNd(BO₃)₂, and a = 7.2113(3) Å, b = 9.9621(4) Å, and c = 10.3347(4) Å for Cs₂LiNd(BO₃)₂. In the structure, NdO₈ polyhedra are corner‐sharing with each other and further interlinked by BO₃ groups to comprise the infinite [Nd₄B₄O₂₄] sheets in the bc plane, with Rb/Cs and Li ions occupying the interlayered space. The compounds show effective near‐IR emission and their associated lifetimes are obtained by fluorescence spectra.     

Complex equilibria of molybdenum(VI) with 2,3-dihydroxynaphthalene

Equilibria of Mo(VI) in acid aqueous solutions with excess of 2,3-dihydroxynaphthalene (DHN)c _DHN /c _Mo = 2.3–107 (I = 0.6 mol 1^–1 (NaClO₄), 0.6% v/v ethanol) were studied spectrophotometrically. Formation constants of MoO₂R ₂ ^2– (logK ₀₁₂ = 5.89±0.01) and presumed MoO₂(OH)(OH₂)R^– (logK ₁₁₁ = 7.79±0.01) chelates were evaluated using SQUAD-G program.     

系列新铌酸盐A6n+[Bxm+Nb12-x]Nb4O42的合成及粉晶X射线衍射分析

０IntroductionNiobateshavemanykindsofstructures．TheseareperovskitetypeABO３（KNbO３），tungstenbronzetypeANb２O６（Ba２NaNb５O１５），chainandlamellartypes犤１～１１犦．SincethenewcompoundK６CrNb１５O４２withakindoftunnelstructureinthepotassiumniobatesystemwasfoundinourlaboratoryforthefirsttime犤１２犦，wehavesynthesizedaseriesofcompoundswiththesamestructure，forexample，K６FeNb１５O４２，K６Ni０．６７Nb１５．３３O４２，Ba６Cr４Nb１２O４２andBa６Ni２．６７Nb１３．３３O４２etc．T…     

Variation of interatomic distances in oxides

The average interatomic distances D in oxygen polyhedra MO _n of isostructural oxides were proposed to be estimated using the equation D = Kɛ(R _M + R _O) or D = Ax ² + Bx + C, where x = ɛ(R _M + R _O), ɛ is the ionicity of the M-O bond, R _M is the ionic radius of the cation M with account for the coordination in the polyhedron, and R _O is the ionic radius of oxygen. Calculations were made for MO oxides having the rock-salt structure; Ln₂O₃ oxides, where Ln = Ce-Yb; and the MO₂ oxides having the rutile and fluorite structures.     

Diffusion behavior of pharmaceutical O/W microemulsions studied by dynamic light scattering

Dynamic light scattering experiments have been performed at various concentrations, of pharmaceutical oil-in-water microemulsions consisting of Eutanol G as oil, a blend of a high (Tagat O2) and a low (Poloxamer 331) hydrophilic–lipophilic balance surfactant, and a hydrophilic phase (propylene glycol/water). We probe the dynamics of these microemulsions by dynamic light scattering. In the measured concentration range, two modes of relaxation were observed. The faster decaying mode is ascribed classically to the collective diffusion D _c (total droplet number density fluctuation). We show that the slow mode is also diffusive and suggest that its possible origin is the relaxation of polydispersity fluctuations. The diffusion coefficient associated with this mode is then the self-diffusion D _s of the droplets. It was found that D _c and D _s had opposite volume fractions of oil plus surfactants (ϕ) dependence and a common limiting value D ₀ for ϕ=0. Average hydrodynamic radius (R _h=10.5 nm) of droplets was calculated from D ₀. R _h is supposed to compose the inner core, a surfactant film including possible solvent molecules, which migrate with the droplet. The concentration dependence of diffusion coefficients reflects the effect of hard sphere and the supplementary repulsive interactions which arises due to loss of entropy, when absorbed chains of surfactant intermingle on the close approach of the two droplets. This mechanism could also explain the observed stability of our systems. The estimated extent of polydispersity is 0.22 from the amplitude of slower decaying mode. The polydispersity in microemulsion systems is dynamic in origin. Results indicate that the time scale for local polydispersity fluctuations is at least three orders of magnitude longer than the estimated time between droplet collisions.