Die IR-Spektren von B-Methoxy- und B-Trideuteromethoxyborazinen und-boroxinen und Tri[methoxy(d3)boran

Zusammenfassung In Methoxyverbindungen des Bors tritt eine Verminderung der Frequenz der B—O-Valenzschwingung gengenüber den entsprechenden Trideuteromethoxyverbindungen auf. Dies wird durch zufällige Entartung von B—O und CH₃ erklärt, die zu einer Abstoßung und zur Vermischung des Schwingungscharakters dieser beiden Schwingungen führt. Hiedurch werden die B—O-Valenzschwingungen zu tieferen und die CH₃-Deformationsschwingungen zu höheren Wellenzahlen verschoben. Ähnliche Erscheinungen sind auch in Methoxyborazinen durch Wechselwirkung von BN und CH₃ zu beobachten. Diese Deutung gibt auch Hinweise für Zuordnungen in den Spektren von N-Methylborazinderivaten.

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In methoxy substituted boron compounds bands arising from B—O stretching and (O)–CH₃ deformation modes show accidental degeneracy. The frequency of the CH₃ absorption is increased whereas BO is decreased compared to the corresponding CD₃-compounds. The spectra of B-methoxyborazines show similar effects between BN and (O)–CH₃ bands, which is analogous to interference between BN and (N)–CH₃ in N-methylborazines.

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Mit 7 Abbildungen     

Enthalpy of formation of triphenylphosphine sulfide

The first measurements of the enthalpies of combustion, sublimation, and fusion of an organo-phosphorus sulfide, triphenylphosphine sulfide, are reported: _c H _m ^o (C₁₈H₁₅PS, cr)=–(10752.58 ±2.90), _sub H _m ^o (C₁₈H₁₅PS, 403 K)=(136.80±6.09), and _fus H _m ^o (C₁₈H₁₅PS, T_m=435.92 K) =(30.53±0.21) kJ·mol^–1. Correction of the phase change enthalpies toT=298.15K and p^o =0.1 MPa results in the standard phase change enthalpy values of _sub H _m ^o (298.15 K)=(142.8 ±6.8) and _fus H _m ^o (298.15 K)=(19.28±0.21) kj·mol^–1. Accordingly, the enthalpies of formation of solid, liquid, and gaseous triphenylphosphine sulfide are derived: _f H _m ^o (C₁₈H₁₅PS, cr) =(63.20±2.56), _fH _m ^o (C₁₈H₁₅PS, l)=(82.48±2.57), and _fH _m ^o (C₁₈H₁₅PS, g)=(206.0±7.3) kJ·mol^–1. From these ancillary data, the P=S double-bond enthalpy is 394 kJ-mol^–1 and in good agreement with earlier reaction calorimetry results. These phosphorus sulfide values are compared with those for the arsenic sulfides. Plausibility arguments are given for our results.     

The mechanisms of the acid-catalysed dissociation of tris-β-diketonatoruthenium(III) complexes

Summary The reactions of four -diketonatoruthenium(III) complexes in the presence of HNO₃ andp-MeC₆H₄SO₃H in the 45° and 57° range were followed spectrophotometrically in Me₂COH₂O mixtures. Dissociation of Ru(acac)₃ follows [H⁺]-dependent and [H⁺]²-dependent paths, whereas the bzac and F₃acacF₃ complexes follow only the [H⁺]-dependent path. The bzbz (Dibenzoylmethanate) complex is inert. Protonation of the bound ligand leads to its rupture from the metal ion. The bzac complex is kinetically more inert than the acac complex, because of extra stability arising from interaction of the (bzac) benzene ring with the pseudo-aromatic diketonate ring of the complex. Considering the kinetic labilities, the complexes may be arranged in the order Ru(F₃acacF₃)₃>Ru(acac)₃>Ru(bzac)₃>Ru(bzbz)₃.Activation parameters for [H⁺] dependent path are: H ₁ 86.5±7, 69±5, 121±7 kJ mol^–1, S ₂ –52±10, –107±10, 57±8 JK^–1 mol^–1 for acac, bzac and F₃acacF₃ complexes respectively and H ₂ 67±5 kJ mol^–1, S ₂ –92±8 JK^–1 mol^–1 for the acac complex only.     

Kinetics of Free Radical Generation in the Catalytic Oxidation of Methanol

The formation of free radicals over the surface of platinum-containing catalysts in the methanol oxidation reaction depending on the temperature, the composition of the reaction mixture, and the procedure used for introducing platinum was studied by the matrix isolation method technique. The nature and transformations of surface intermediates depending on the temperature and the presence of oxygen in the gas phase were studied by Fourier transform IR spectroscopy. The main surface intermediate was the methoxy group. The following three types of these groups were stabilized in alumina-based catalysts: (I) CH₃O–Al_oct (_s(–) = 2806 cm^–1), (II) CH₃O–Al_tetr (_s(–) = 2825 cm^–1), and (III) CH₃O < (Al)₂ (_S(–) = 2845 cm^–1, _s(–) = 1460 cm^–1, _s(–) = 1440 cm^–1, r _|| (₃) = 1185 cm^–1, and (–) = 1095 cm^–1). At the same time, isolated methoxy groups (_as(–) = 2997 cm^–1, _as(–) = 2959 cm^–1, _s(–) = 2857 cm^–1, and (₃) = 1450 cm^–1) and hydrogen-bonded groups ((–) = 3400–3550 cm^–1), which resulted from chemisorption at siloxane bridges, were stabilized in silica gel–based catalysts. It was found that CH₃O and CH₃OO radicals were formed only over the surfaces of pure supports (SiO₂ and Al₂O₃) and their mechanical mixtures with platinum. The total concentration of radicals was described by an extremal function of the composition of reactants, whereas the relative concentration depends on the nature of the support. This is conceivably due to the effect of coordinatively unsaturated cations of the support, which are formed by dehydroxylation in the course of catalyst pretreatment. An increase in the rate of formation of gas-phase radicals on mixed catalysts was explained by special properties of the platinum/support interface region, at which surface intermediates were formed in superequilibrium concentrations under reaction conditions.     

Effect of pressure on the solubility of naphthalene in water at 25°C

Solubility of naphthalene in water was measured at 25°C and pressures up to 200 MPa. The solubility decreased with increasing pressure. From the pressure coefficient of the solubility, the volume change V accompanying the dissolution was estimated as 13.8±0.4 cm ³ -mol ^–1 . Further we estimated the volume change V _CH accompanying hydrophobic hydration as –0.1±0.6 cm ³ -mol ^–1 using the V value, the molar volume of crystalline naphthalene, and the partial molar volume of naphthalene in n-heptane. This V _CH is much larger (i.e., less negative) than that for hydrophobic hydration of alkyl-chain compounds and suggests that the hydration structure of naphthalene differs from that of alkyl-chain compounds.     

DSC and X-ray studies on side-chain crystallization of comb-like polymers

Thermal properties of acrylate and methacrylate monomers containing long-fluorocarbon chains (H(CF₂)_nCH₂OCOCH=CH₂, (F_nA) and H(CF₂)_nCH₂OCOC(CH₃)=CH₂, (F_nMA), wheren=6, 8, 10) and their comb-like polymers have been investigated by differential scanning calorimeter (DSC) and X-ray diffraction. The comb-like polymers (PF₁₀A and PF₁₀MA) with sufficiently long-fluorocarbon chains showed a simple melting and crystallizing behavior. For the fusion of PF₁₀A in 1st heating, enthalpy change H _f was 18 kJ mol^–1 and entropy change S _f was 45 J K^–1 mol^–1, while for PF₁₀MA the values H _f and S_f were 5.3 kJ mol^–1 and 14 J K^–1 mol^–1, respectively. Melted PF₈A crystallized slowly, whereas PF₈MA with same fluorocarbon chain and also both of PF₆A and PF₆MA with shorter fluorocarbon chains can hardly crystallize by the aggregation of side-chains. Effects of the length of side-chain and the flexibility of main chain on the side-chain crystallization of comb-like polymers are clear. Crystallization process of the methacrylate monomers was sensitively affected by the scanning rate of DSC measurement and the length of fluorocarbon chains.     

Transport and electrocatalytic properties of La0.3Sr0.7Co0.8Ga0.2O3−δ membranes

Incorporation of gallium into the perovskite lattice of La_0.3Sr_0.7CoO_3– leads to increasing unit cell volume and to decreasing thermal expansion, total conductivity and oxygen permeability. At 973–1223 K, the oxygen permeation fluxes through La_0.3Sr_0.7Co_0.8Ga_0.2O_3– ceramics with 96.5% density are determined by the bulk ionic conduction and surface exchange rates. The total conductivity of La_0.3Sr_0.7Co_0.8Ga_0.2O_3–, predominantly p-type electronic, exhibits an apparent pseudometallic behavior due to oxygen losses on heating, whereas the p(O₂) dependencies of the conductivity and Seebeck coefficient suggest a small-polaron mechanism of hole transport. The average thermal expansion coefficients in air are 15.9×10^–6 K^–1 at 360–710 K and 27.9×10^–6 K^–1 at 710–1030 K. On decreasing oxygen pressure down to 4–30 Pa at 973–1223 K, perovskite-type La_0.3Sr_0.7Co_0.8Ga_0.2O_3– transforms into a brownmillerite-like modification, whose electrical properties are essentially p(O₂) independent. Further reduction results in the decomposition of the brownmillerite into a multiphase oxide mixture at p(O₂)=8×10^–10–3×10^–4 Pa, and then in the segregation of metallic cobalt. Due to surface-limited oxygen transport, La_0.3Sr_0.7Co_0.8Ga_0.2O_3– membranes are, however, kinetically stable under an air/CH₄ gradient up to 1223 K. The conversion of dry methane in model membrane reactors increases with oxygen permeation flux and temperature, but yields high CO₂ concentrations (>90%), indicating a dominant role of complete CH₄ oxidation on the membrane surface.     

Temperature dependence of the quadrupole splitting and μeff for [FeCl2(Dena)4]·DmgH2

Mössbauer spectrometry and magnetochemical methods have been applied to a complex known as catene: -dimethylglyoxime dichlorotetra(N,N-diethylnicotinamide) iron· (II) [FeCl₂(Dena)₄]·DmgH₂, where Dena is N,N,diethylnicotinamide and DmgH₂ is dimethylglyoxime. The compound has a high-spin state for the iron(II) (S=2). The magnetic susceptibility follows the Curie-Weiss law with a small value of , The E_Q=f(T) relation shows that the symmetry of the immediate environment of the iron is less than tetragonal: ₁=190 cm^–1, ₂=490 cm^–1.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, No. 1, pp. 56–60, January–February 1992.     

IR-Untersuchungen an B-Tris (dimethylamino) boroxin und B-Tris[dimethylamino (d6)] boroxin

Zusammenfassung In B-Tri(dimethylamino)boroxin zeigt — im Gegensatz zum B-Trimethoxyboroxin — die B–O-Hauptbande nur geringe Kopplung mit CH₃-Deformationsschwingungen. Die B–N-Valenzbande tritt hingegen mit _sCH₃ in Wechselwirkung, wodurch Banden mit gemischtem Schwingungscharakter entstehen. In der deuterierten Verbindung liegt BN verkoppelt mit BO bei 1461 cm^–1

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In B-Tri(dimethylamino)boroxin coupling between the B–O ring stretching main-band and CH₃ is weak in contrast to B-trimethoxyboroxine. Interference between BN and CH₃ leads to bands of mixed character, one of them is above 1500 cm^–1. In [(CD₃)₂NBO] BN coupled with BO is at 1461 cm^–1.

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Mit 2 Abbildungen     

Solvent and Temperature Dependence of 59Co NMR Chemical Shifts of Tris(acetylacetonato)cobaIt(III) and Tris(dipivaloylmethanato)cobalt(III)

Cobalt-59 NMR chemical shifts of Co(acac)₃, and Co(dpm)₃ (acac^– = acetylacetonate ion and dpm^– = dipivaloylmethanate ion) in 14 organic solvents, C₆H₁₄, C₆H₆, CH₂Cl₂, CHCl₃, CCl₄, CH₃CN, CH₃OH, C₂H₅OH, CH₃CH(OH)CH₃, (C₂H₅)₂O, (CH₃)₂CO, (CH₃)₂SO, (CH₃)₂NCHO and C₆H₅NO₂, were measured at five temperatures ranging from 289 to 329 K. The observed chemical shift (_obs) was linearly correlated to the maximum absorption wavelength in the visible spectra (_max) corresponding to the d-d electronic transition energy between the ground ¹A_1g and excited ¹T_1g states. The _obs-_max relation was explained by the ligand field theory. The temperature coefficients of _obs, of each complex showed a negative correlation with _obs. The _obs, of Co(acac)₃ decreased with the increasing electrophilic ability of the solvent (Mayer's acceptor number), whereas no tendency was observed in the case of Co(dpm)₃.     

The influence of pentaamminerhodium(III) on the1H n.m.r. spectra and pyrrole pKas of coordinated imidazoles and pyrazoles

Summary The following [(NH₃)₅RhLH]Cl₃ salts were preparedvia the [(NH₃)₅Rh(O₃SCF₃)](O₃SCF₃)₂ synthetic route; LH=1-methylimidazole (1CH₃imH), 2-methylimidazole (2CH₃imH), 4-methylimidazole (4CH₃imH), 5-methylimidazole(5CH₃imH), and pyrazole (pyzH). pK_a's at 25.0°C were determined for [(NH₃)₅RhLH]³⁺ complexes as follows: 2CH₃imH, 10.4±0.1; 5CH₃imH/4CH₃imH isomer mixture, 10.3±0.1; pyzH, 6.54±0.05. The influence on the pK_a's of imidazoles is dominated by withdrawal of the rhodium(III) centre and may be compensated by the presence of ring methylation by only 0.5log units for cobalt(III) and rhodium(III) derivatives, compared to 1.3 units for the -withdrawing ruthenium(III) centre. In the case of the -acceptor pyrazole ring, [(NH₃)₅Rh]³⁺ is observed to serve as a slight -donor and raises the pK_a above the cobalt(III) analogue. The¹H n.m.r. spectra of [(NH₃)₅RhLH]³⁺ complexes of the substituted imidazoles and pyrazole exhibit a deshielding order. C–2H>C–5H>C–4H for imidazoles and C–3H>C–5H>C–4H for pyrazole, as do their cobalt(III) analogues. The magnitude of values (=_{free L}-_complex) are virtually the same as in the cobalt(III) systems which shows that TIP influences are unimportant compared to ring rehybridization in estabilishing chemical shifts for both the cobalt(III) and rhodium(III) complexes. The imidazolato and pyrazolato complexes exhibit resonances upfield of the respective substituted imidazole or pyrazole complex in keeping with more negative charge on the rings; the influence is largest at C–2H of imidazolates and C–3H of pyrazolate.     

étude thermodynamique de certains médicaments

Two compounds of sulphamide type:p-amino-benzene sulphonamide (I) and 3,4-dimethylisoxazol 5-sulphanylamide (II) were studied by combustion calorimetry and by differential scanning calorimetry (DSC).The enthalpies in solid state at 298,15 K of combustion, _c H _m ^o (I)=-2788,5±1,6 kJ mol^–1, _c H _m ^o (II)=-5036±3,8 kJ mol^–1 and of formation, _f H _m ^o (I)=-458,3±1,6 kJ mol^–1, _fH _m ^o (II)=-180,1±3,8 kJ mol^–1 were determined.The thermal effects concerning the melting and phase transition of this compounds were also measured.

     

Preparation and properties of compact cubic δ-NbN1−x

Compact -NbN_1–x was prepared by heating niobium wire for several days in nitrogen at 4 MPa pressure and temperatures of 1 723 to 1 923 K. The samples obtained had compositions between NbN_0.924 and NbN_0.975±0.002 and were coarse-grained. The lattice parameter increases with the nitrogen content froma=0.43884 nm for NbN_0.924 toa=0.43913 nm for NbN_0.975. From the determination of the lattice parameters up to 1 073 K the coefficient of linear thermal expansion as a function of temperature was evaluated. The microhardness HV_0.1 decreases from 1 300±80·10⁷Nm^–2 for NbN_0.924 to 1080±60·10⁷ Nm^–2 for NbN_0.975. The occupancies of both the niobium and the nitrogen sublattices were calculated using experimental density data. The occupancy of the niobium sublattice decreases linearly with increasing nitrogen content. An extrapolation gives 2.9±0.4% vacancies in both sublattices for stoichiometric -NbN.

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Herstellung und Eigenschaften von kompaktem, kubischem -NbN_1–x

Zusammenfassung Kompaktes -NbN_1–x wurde durch mehrtägiges Erhitzen von Niobdraht in Stickstoff bei einem Druck von 4 MPa und Temperaturen von 1 273 bis 1 923 K hergestellt. Die dabei erhaltenen Proben hatten Zusammensetzungen von NbN_0.924 bis NbN_0.975±0.002 und zeigten ein grobkörniges Gefüge. Der Gitterparameter steigt mit dem Stickstoffgehalt vona=0.43884 nm für NbN_0.924 bisa=0.43913 nm für NbN_0.975 an. Von einer Bestimmung der Gitterparameter bis 1 073 K wurde der lineare thermische Ausdehnungskoeffizient erhalten. Die Mikrohärte HV_0.1 sinkt von 1 300±80·10⁷ Nm^–2 für NbN_0.924 auf 1 080±60·10⁷ Nm^–2 für NbN_0.975 ab. Die Besetzung sowohl des Niob- als auch des Stickstoffteilgitters wurde unter Verwendung von experimentell gemessenen Dichten bestimmt. Die Besetzung des Niobteilgitters fällt mit zunehmendem Stickstoffanteil linear ab. Eine Extrapolation dieser Werte ergibt für stöchiometrisches -NbN einen Leerstellenanteil von 2.9±0.4% auf beiden Teilgittern.

     

Reaction of Ru(PPh3)3Cl2 with arylazoimidazoles: spectral characterisation and redox studies of [bis-{N(1)-alkyl-2-(arylazo)imidazole}-bis-(triphenylphosphine)]-ruthenium(II) perchlorate

Ru(PPh₃)₃Cl₂ reacts with N(1)-alkyl-2-(arylazo)imidazoles, p-RC₆H₄N=NC₃H₂N₂X, [RaaiX, R = H(a), Me(b), Cl(c); X = Me(1), Et(2), Bz(3)] under refluxing conditions in EtOH to give [Ru(RaaiX)₂(PPh₃)₂](ClO₄)₂ · H₂O complexes (4–6). RaaiX is a bidentate chelator (N, N) with N(imidazole), N and N(azo), N donor centres. Three isomers are present in the mixture in which the pairs of PPh₃, N and N occupy cis–cis–trans, cis–trans–cis and cis–cis–cis, positions respectively. The isomers were identified by ¹H-n.m.r. spectra. Four signals are observed in the aliphatic zone for N(1)-X; two are of equal intensity at higher and the other two signals at lower in the ratio 1:0.3:0.2 suggesting the presence of cis–cis–cis, cis–trans–cis and cis–cis–trans-geometry. The complexes display the allowed t ₂(Ru) ^*(RaaiX) transition. Cyclic voltammetry indicates two consecutive Ru^III/II couples along with azo reductions.     

Substituent Distribution of Cyanoethyl Cellulose

Estimation of the substitution distribution for cyanoethyl cellulose was carried out by ¹H and ¹³C NMR spectroscopic analyses after the additional acetylation. Based on the complemental function of cyanoethyl and acetyl substituents, the degree of substitution (DS) of cyanoethyl groups could be calculated from the ratios of the ¹H integrated intensities in acetyl methyl ( 1.8–2.1) and cyanoethyl methylene ( 2.6–2.9) protons, and also from the corresponding ratios for acetyl methyl carbon signals ( 19.7–21.3) and cyanoethyl methylene carbon signals ( 17.5–19.0). Good agreement was obtained between the DS values obtained from the NMR spectroscopic analyses and those determined by the conventional nitrogen content method, indicating the validity of the NMR method used. In addition, the NMR method was found to be effective in determining the positional substituent distribution by the quantitative analysis of the three cyan carbon signals ( 118–120).     

Magnetic properties of transition metal ion cubic 5T2 terms in axial ligand fields

The theory of magnetic anisotropy and susceptibility is worked out for cubic ⁵T₂ terms, the degeneracy of which is partially lifted by a ligand field component of axial symmetry as well as by spin-orbit coupling. Matrix elements are calculated by application of the method of Abragam and Pryce to a set of M.O. based wave-functions. The anisotropy in covalency of the metal-ligand bond and in spin-orbit coupling is taken into account. Numerical values of principal magnetic moments, P and P , are calculated as function of kT/, /, and .The theoretical results are employed in a rigorius analysis of existing single crystal magnetic data on high-spin iron(II) compounds. For (NH₄)₂Fe(SO₄)₂·6 H₂O, =–100 cm^–1, =1070 cm^–1 and =0.8 to 0.6 is obtained. For FeSiF₆·6 H₂O, =–80 cm^–1, =–760cm^–1 at 77.3K and –580 cm^–1 between 20.4 and 1.57K, and 0.7 is derived. No unique fit is possible for K₂Fe(SO₄)₂·6 H₂O. The data are reproduced to better than ±1% in most cases. The limitations of the approach are stressed.

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Zusammenfassung Die Theorie der magnetischen Anisotropie und der magnetischen SuszeptibilitÄt eines ⁵ T ₂ Grundterms im oktaedrischen Ligandenfeld wird für den Fall entwickelt, da\ die Entartung unter dem Einflu\ einer axial-symmetrischen Feldkomponente sowie der Spin-Bahn-Wechselwirkung teilweise aufgehoben ist. Eigenfunktionen werden auf der Grundlage der M.O.-Theorie aufgestellt, Matrixelemente mittels der Theorie von Abragam und Pryce ermittelt. Der Anisotropie der Metall-Ligand-Bindung sowie der Spin-Bahn-Kopplung wird Rechnung getragen. Numerische Werte für die magnetischen Hauptmomente P und P werden in AbhÄngigkeit von kT/, / und berechnet.Die Ergebnisse der Theorie werden für eine genaue Analyse der verfügbaren magnetischen Daten aus Messungen an Einkristallen magnetisch normaler Eisen(II)-Verbindungen verwendet. Für (NH₄)₂Fe(SO₄)₂·6 H₂O werden =–100 cm^–1, = 1070 cm^–1 und = 0,8 bis 0,6 erhalten. Für FeSiF₆·6 H₂O ergeben sich =–80 cm^–1, =–760 cm^–1 bei 77,3K und =–580 cm^–1 zwischen 20,4 und 1,57K sowie 0,7. Die experimentellen Daten können in den meisten FÄllen auf ±1% genau oder besser wiedergegeben werden. Bei K₂Fe(SO₄)₂·6 H₂O gelang keine eindeutige Bestimmung der theoretischen Parameter. Die Grenzen der vorliegenden Behandlung werden kritisch diskutiert.

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Résumé La théorie de l'anisotropie magnétique et de la susceptibilité magnétique est développée pour les termes cubiques ⁵ T ₂, dont la dégénérescence est partiellement levée par une composante à symétrie axiale du champ de ligandes ainsi que par le couplage spin-orbite. Les éléments de matrice sont calculés à l'aide de la méthode d'Abragam et Pryce employée sur un système M.O. des fonctions d'onde de base. On a pris en consideration l'anisotropie de la liaison entre le metal et le ligand et aussi du couplage spin-orbite. Les valeurs numériques des moments magnétiques principaux P et P sont calculées en fonction de kT/, /, et .Les résultats théoriques sont employés dans une analyse détaillée des données magnétiques disponibles sur monocristaux des composés ferreux spin-élevés. Pour (NH₄)₂Fe(SO₄)₂·6 H₂O on a obtenu =–100 cm^–1, =1070 cm^–1 et =0.8 à 0,6. Pour FeSiF₆·6 H₂O on a eu comme résultat =–80 cm^–1, =–760 cm^–1 à 77,3 K et =–580 cm^–1 entre 20,4 et 1,57K avec 0,7. Les valeurs expérimentales sont réprésentées dans la plupart de cas plus précises que ±1%. Au cas de K₂Fe(SO₄)₂·6 H₂O une détermination unique était impossible. Les limites de cette approximation sont discutées.

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Postdoctoral Fellow, Theoretical Chemistry, 1963–1964.     

Electrostriction of polymethylmethacrylates

Electrostriction of tactic polymethylmethacrylates in response to step-on and step-offdc-fields was investigated in the field strength range from 1 to 5 MV m^–1 at room temperature; one example of electrostriction under sinusoidal field is given.Three principal retardation time regions were found: ₁=1.5 s, ₂=30 s, and ₃=140 s, each field strength independent. The retardation strengths belonging to these electrostrictive processes depend on tacticity.The low frequency limit of the electrostrictive volume compliance for the investigated PMMA is _a =–1.2×10^–15 m² V ^–2 for atactic, _S =–2.3×10^–14 m² V ^–2 for syndiotactic, and _i=–4.5 × 10^–14 m² V ^–2 for isotactic PMMA.Herrn Prof. Dr. F. H. Müller gewidmet.     

IR-Spektroskopische Untersuchungen an 1,3-Dioxa- und 1,3-Diaza-2-boracyclopentanderivaten

Zusammenfassung Die IR-Spektren von mehreren Dioxa- und Diazaboracyclopentanderivaten wurden zusammen mit jenen von C-deuterierten Verbindungen untersucht. Besonderer Wert wurde auf die Klärung von Kopplungen zwischen BN-, BO- und CH₃-Schwingungen im Bereich zwischen 1550 bis 1300 cm^–1 gelegt.

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IR-spectra of several dioxa- and diaza-boracyclopentanes have been studied together with those of some C-deuterated analogues. Special attention has been given to coupling effects of BN-, BO-, and CH₃-modes in the 1550–1300 cm^–1 region.

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Mit 3 Abbildungen     

Partition coefficients of ω-phenylalkanols between water and sodium deoxycholate micelles

The partition coefficient of -phenylalkanols [C₆H₅(CH₂)_mpOH, m _p =3–6] between water and micelles of sodium deoxycholate (NaDC) has been determined by a differential spectroscopic method at 25°C. The linear dependence of thestandard free energy change of transfer calculated from the partition coefficient on the alkyl chain length of the alkanols (m _p 4) yields the standard free energy change per methylene group [G^o(CH₂)]. G^o(CH₂) value for the present system, –3.21 kJ-mol ^–1 is larger in magnitude than that for sodium dodecylsulfate (SDS)--phenylalkanol system, –2.40 kJ-mol ^–1 . The result indicates that the alkyl chain of -phenylalkanols has higher affinity to NaDC micelles than to SDS micelles although the molecular structure of NaDC is more rigid and bulkier than that of SDS and the aggregation number of micelles of the former is much smaller than that of micelles of the latter. On the basis of the linear relation between the effect of added -phenylalkanols on the critical micelle concentration of NaDC (–dC_cmc/dC_a) and the partition coefficient, it is found that the degree of ionization of NaDC micelles is not influenced by solubilization of -phenylalkanols into the micelles.     

Mössbauer spectroscopic studies in alkali metal hexakis (trimethylacetato) ferrate(III) complexes and their thermal decomposition products

Mössbauer spectra of hexakis (trimethylacetato) ferrate(III) complexes with general formula M₃[Fe{OCOC(CH₃)₃}₆] (where M=H⁺, Li⁺, Na⁺, K⁺ and NH ₄ ⁺ ) exhibit a quadrupole doublet with E_Q=0.31–0.65 mms^–1 and =0.60–0.74 mms^–1 (with respect to S.N.P. as standard). Infrared studies suggest unidentate coordination of the carboxylate ligands. Anomalously high and E_Q values for H₃[Fe{OCOC(CH₃)₃}₆] have been explained in terms of possible hydrogen bonding. Thermal decomposition studies show fast and single stage decomposition yielding a constant weight at 320°C. Mössbauer spectra of intermediates after heating complexes at different temperatures indicate increasing E_Q values. At 350°C, all complexes exhibit six-line spectra, suggesting the formation of alkali metal ferrate (Na₂O·NaFeO₂) or Fe₂O₃.