ISSN:0005-9021    

DOI:10.1002/bbpc.19850890702

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1985

数据来源: WILEY

摘要:

AbstractThe equilibrium constants for the complex formation of Fe(H2O)3+6with SCN−(K1) and the hydrolysis of Fe(H2O)5SCN2+to produce Fe(H2O)4(OH)SCN+(K4) were studied as a function of ionic strength (0.1 to 1.5 M) at 25°C and pressures up to 120 MPa. The ionic strength dependencies at ambient pressure can be expressed as logK1= 2.86 ‐ 3.05 √ μ (1 + 2.96 √ μ)−1+ 0.04 μ and logK4= ‐0.93 ‐ 1.02 √ μ (1 + 1.97 √ μ)−1+ 0.06 μ, from which the distance of closest approach follows to be 0.9 and 0.6 nm, respectively. The pressure dependencies ofK1andK4result in reaction volumes ranging from 10.0 to 7.5 and 11.9 to 11.0 cm3mol−1, respectively, for zero to 1.5 M ionic strength. These data combined with those for the hydrolysis of Fe(H2O)3+6reported before, enable the estimation of the equilibrium constant (K3) for the formation of Fe(H2O)4(OH)SCN+from Fe(H2O)5OH2+and SCN−, as a function of ionic strength and pressure. This is the first study to report such data for K3, and K4, and the results are discussed in reference

ISSN:0005-9021    

DOI:10.1002/bbpc.19850890703

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1985

数据来源: WILEY

摘要:

AbstractThe kinetics of the reactions of the nitroprusside ion — pentacyanonitrosylferrate(II) — with various secondary amines have been studied in basic media. Two parallel reaction pathways are involved: (i) the reaction of the nitroprusside ion with hydroxyl ions to form Fe(CN)5NO4+2, in which NO−2is then replaced by the amine; and (ii) the reaction of the nitroprusside ion with two molecules of amine to form the corresponding nitrosamine and the complex Fe(CN)5NHR3‐2. The corresponding rate equations have been obtained and explained by proposed reaction mechanisms. We propose a concerted mechanism for reaction (ii) in which the amine binds the nitrosyl group at the same time as the amine proton is removed by a base catalyst. The resulting nitrosamine complex subsequently undergoes substitution by the amine in a fast

ISSN:0005-9021    

DOI:10.1002/bbpc.19850890704

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1985

数据来源: WILEY

摘要:

AbstractPotassium bromide treated with bromine and chlorine vapor respectively, was used as catalyst for the dehydrochlorination of t‐butyl chloride. The results indicated a clear correlation between the presence of color centers (V‐centers) in the halides and their catalytic activity. The activation energies of the catalytic dehydrochlorination were measu

ISSN:0005-9021    

DOI:10.1002/bbpc.19850890705

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1985

数据来源: WILEY

摘要:

AbstractThe dielectric properties of Carboxymethylcellulose in various uni‐univalent electrolyte solutions in the frequency range from 1 KHz to 10 MHz have been measured by means of a conventional impedance bridge technique. — Two contiguous dielectric dispersions, due to different molecular mechanisms, have been observed, in accordance with the usual behaviour of linear, high‐charged polyelectrolytes. — The influence of the molecular weight, polyion concentration and different monovalent counterions (Na+, K+, Li+) has been examinated. — The results are analyzed in terms of rod‐like polyelectrolyte dielectric models taking into account the polarization due to the fluctuation in the counterion co

ISSN:0005-9021    

DOI:10.1002/bbpc.19850890706

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1985

数据来源: WILEY

摘要:

AbstractA new method to measure the water (D2O/H2O) permeation across vesicular lipid bilayers is described. The method is based on the solvent isotope effect of the light scattering which is a consequence of the different indices of refraction of D2O and H2O. Unilamellar lipid vesicles in excess of H2O are rapidly mixed with D2O or vice versa. As result of the H2O/D2O exchange across the vesicular bilayer the light scattering signal has a time dependent, almost single exponential component allowing the deduction of the exchange relaxation ratekexand, at known size, of the permeability coefficient,Pd. The experimental results are in accord with calculations from the Mie theory of light scattering for coated spheres. The method is applicable for large vesicles where the permeation is the rate‐limiting step. Size separations are performed by a flow dialysis through a sequence of pore‐membrane‐filters. For dimyristoyl‐lecithin bilayers the water permeability‐coefficient is 1.9 · 10−5cm/s in the crystalline phase and increases by a factor of 10–100 in the liquid‐crystalline state. The temperature dependence of the permeation exhibits a sharp change at the phase transition. For binary mixtures of lecithins this sharp change follows the solidus curve of the non‐ideal phase diagram determined by spectr

ISSN:0005-9021    

DOI:10.1002/bbpc.19850890707

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1985

数据来源: WILEY

摘要:

AbstractAn empirical relation between diffusion coefficients and viscosities is proposed which interpolates between the kinetic theory of dilute gases and the Stokes‐Einstein equation of liquids. This extended Stokes‐Einstein‐relationship is tested with experimental examples. It is useful for studies of reaction processes over large density r

ISSN:0005-9021    

DOI:10.1002/bbpc.19850890708

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1985

数据来源: WILEY

摘要:

AbstractDifferential scanning calorimetry, the temperature dependence of proton and deuteron lineshapes and spin‐lattice relaxation times are reported for (CH3)2NH2ClO4and its selectively deuterated analogue (CH3)2ND2ClO4. Our caloric data revealed the existence of three different phase modifications in dimethylammonium perchlorate, analogous to mono‐ and trimethylammonium perchlorate. An analysis of the NMR data enabled identification of the molecular motions occurring in the respective phases and to determine their activation parameters. In the low‐temperature phase III stable below 309 K there are two inequivalent dimethylammonium cations which manifest themselves by different reorientation frequencies of methyl groups about their threefold symmetry axes C3and by reorientation of one of the two inequivalent cations about its pseudo threefold symmetry axis C'3lying along one of the two ND bonds. In the low‐temperature range of this phase the deuteron quadrupole coupling constant indicates NH…O hydrogen bonds between the dimethylammonium and the perchlorate ions. The intermediate phase II has not been reported so far. It is stable in the temperature range 309 – 311 K, but can easily be undercooled below 290 K. In this phase one of the two cations undergoes reorientation about its diad C2axis, whereas the other still reorients about the C'3axis. The analysis of the large entropy change of 25.5 J/mol · K associated with the III−II transition indicates that the ClO4ions in phase II have considerable motional freedom, presumably due to breaking of N  H… O hydrogen bonds. In phase I the dimethylammonium cations undergo quasiisotropic reorientation about their centers of gravity and translational diffusion between different sites of th

ISSN:0005-9021    

DOI:10.1002/bbpc.19850890709

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1985

数据来源: WILEY

摘要:

AbstractThe chemical shifts of the methyl protons of acetonitrile were measured at 298 K as a function of concentration in 6 aromatic solvents. The local structure of the solutions are interpreted by using the model of hard convex bodies, assuming anisotropic aromatic shielding terms and intermolecular repulsive forces. So the angels α can be determined, which show the intermolecular orientation between the acetonitrile and the aromatic molecules. This way it is possible to calculate the angles β of the orientation between the aromatic molecules. Two different kinds of aromatic solvents could be identified:abenzene, furane, thiophene‐ with intermolecular plane to plane angle β ≈ 60°bpyridazine, pyridine, pyrimidin‐ with intermolecular plane to plane angl

ISSN:0005-9021    

DOI:10.1002/bbpc.19850890710

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1985

数据来源: WILEY

摘要:

AbstractIn the course of a systematic investigation of some compounds of uranium (IV), several physico‐chemical methods have been applied to the salts of the series UX4and M2UX6(with X = Cl, Br, I and M = Li, Na, K, Rb, Cs). ‐ The results obtained in the present work refer to UCl4; they have been obtained by electrical conductivity measurements, by differential thermal analysis and by differential enthalpic analy

ISSN:0005-9021    

DOI:10.1002/bbpc.19850890711

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1985

数据来源: WILEY