The effect of surfactant charge on micellization behavior

 The influence of the surfactant charge on micellization was studied on sodium n-dodecane-phosphonates, varying the charge of the surfactant ion from 0 to 2. The effects on the cmc, hydrolysis, micelle composition, and micelle ionization degree were studied. The increase of one e unit in the charge of the surfactant species reduces the cmc by about one order of magnitude. Received: 18 November 1996 Accepted: 5 March 1997     

Darstellung und spektroskopische Untersuchungen von hoch-verzweigten funktionellen Siloxanen

Preparation and Spectroscopic Investigations of Highly Branched Functional Siloxanes The preparation of the siloxanes [(Me₃SiO)₃SiO]_n(Me₃SiO)_3?nSiX and (Me₃SiO)₃Si[OSi(OSiMe₃)₂]₂X (n = 1?3, X = H, Cl, OC₂H₅, OH) is described. The hydride-siloxanes and the siloxanoles have been investigated by i.r. and ²⁹Si-n.m.r. spectroscopy. The frequencies of the Si? H stretching vibration, the ²⁹Si? ¹H coupling constants and the ²⁹Si-chemical shifts of the Si(H) signal for the hydride-siloxanes as well as the frequencies of the (Si)O? H stretching vibration, the relative (Si)O? H acidity, and the ²⁹Si-chemical shifts of the Si(OH) signal for the siloxanoles show a dependence on the number of the (Me₃SiO)₃SiO groups. The spectroscopic data are discussed with respect to the silicate environment of the Si(H) and Si(OH) atom, respectively. In the siloxanoles intramolecular hydrogen bondings were observed.     

Effect of the sixth axial ligand in CS-ligated iron(II)octaethylporphyrinates: structural and Mössbauer studies

The effect of a sixth ligand in a series of low-spin thiocarbonyl-ligated iron(II)octaethylporphyrinates has been investigated. Six-coordinate complexes have been synthesized and characterized by M?ssbauer and infrared spectroscopy and single-crystal X-ray structure determinations. The results are compared with the five-coordinate parent complex. The crystal structures of [Fe(OEP)(CS)(1-MeIm)] and [Fe(OEP)(CS)(Py)] are reported and discussed. The 1-methylimidazole and pyridine derivatives exhibit Fe-C(CS) bond distances of 1.703(4) and 1.706(2) A that are significantly longer than the 1.662(3) A reported for five-coordinate [Fe(OEP)(CS)] (Scheidt, W. R.; Geiger, D. K. Inorg. Chem. 1982, 21, 1208). The trans Fe-N(ligand) distances of 2.112(3) and 2.1550(15) A observed for the 1-methylimidazole and pyridine complex are approximately 0.13 A longer than those observed for analogous bis-ligated complexes and are consistent with a significant structural trans effect for the CS ligand. M?ssbauer investigations carried out for five- and six-coordinate thiocarbonyl derivatives with several different sixth axial ligands reveal interesting features. All derivatives exhibit very small isomer shift values, consistent with a very strong interaction between iron and CS. The five-coordinate derivative has delta(Fe) = 0.08 mm/s, and the six-coordinate complexes exhibit delta(Fe) = 0.14 to 0.19 mm/s at 4.2 K. The five-coordinate complex shows a large quadrupole splitting (DeltaE(q) = 1.93 mm/s at 4.2 K) which is reduced on coordination of the sixth ligand (DeltaE(q) = 0.42-0.80 mm/s at 4.2 K). Addition of a sixth ligand also leads to a small decrease in the value of nu(CS). Correlations in structural, IR, and M?ssbauer results suggest that the sixth ligand effect is primarily induced by changes in sigma-bonding. The structure of [Fe(OEP)(CS)(CH(3)OH)] is briefly reported. Crystal data: [Fe(OEP)(CS)(1-MeIm)] crystallizes in the monoclinic system, space group P2(1)/n, Z = 4, a = 9.5906(5) A, b = 16.704(4) A, c = 23.1417(6) A, beta = 100.453(7) degrees. [Fe(OEP)(CS)(Py)] crystallizes in the triclinic system, space group P1, Z = 5, a = 13.9073(6) A, b = 16.2624(7) A, c = 22.0709(9) A, alpha = 70.586(1) degrees, beta = 77.242(1) degrees, gamma = 77.959(1) degrees. [Fe(OEP)(CS)(CH(3)OH)] crystallizes in the triclinic system, space group P1, Z = 1, a = 9.0599(5) A, b = 9.4389(5) A, c = 11.0676(6) A, alpha = 90.261(1) degrees, beta = 100.362(1) degrees, gamma = 114.664(1) degrees.     

Hydrogenation of alkenes catalyzed by supported Ziegler catalysts

Supported Ziegler catalysts prepared by the reaction of a Ni(II) 1-butylsalicylaldiminate or Ni(II) 2-ethylhexanoate with Al₂O₃/SiO₂ treated with AlEt₃ or NaAlH₂ (OCH₂CH₂OCH₃)₂ are efficient catalysts for hydrogenation of simple alkenes. The factors influencing their activity are reported.

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, qp - Ni(II) - Ni(II) 2- Al₂O₃/SiO₂, AlEt₃ NaAlH₂ (OCH₂CH₂OCH₃)₂, . , .

     

Spektroskopische Untersuchungen zu Substituenteneffekten in Silylmethylsilanen

Spectroscopic Investigations on Substituent Effects in Silylmethylsilanes The silanes Me_3?n(Me₃SiCH₂)_nSiH (n = 1–3), (RMe₂SiCH₂)₃SiH (R = n-Bu, n-Pr, Et, PhCH₂, Ph) and Me₃ElCH₂SiMe₂H (El = Ge, Sn) were prepared. The frequencies of the Si? H stretching vibration, the ²⁹Si? ¹H coupling constants and the ²⁹Si n.m.r. chemical shifts were measured. The ?(SiH) and J(²⁹Si? ¹H) values in the silanes Me_3?n(Me₃SiCH₂)_nSiH depend on the number of trimethylsilymethyl groups. There is hardly an influence of the substituents R on these values in the silanes (RMe₂SiCH₂)₃SiH. The frequencies of the Si? H stretching vibrations in the silanes Me₃ElCH₂SiMe₂H (El = Si, Ge, Sn) show the order Si?Ge > Sn. The ₂₉Si n.m.r. chemical shifts of the Si(H) signals are approximately equal in the silanes Me_3?n(Me₃SiCH₂)_nSiH and (RMe₂SiCH₂)₃SiH.     

Structural determination of neutral O-linked oligosaccharide alditols by negative ion LC-electrospray-MS<Superscript>n</Superscript>.

Neutral O-linked oligosaccharides released from the salivary mucin MUC5B were separated and detected by negative ion LC-MS and LC-MS(2). The resolution of the chromatography and the information obtained from collision induced dissociation of detected [M - H](-) ions were usually sufficient to identify the sequence of individual oligosaccharides, illustrated by the fact that 50 different oligosaccharides ranging from disaccharides to nonasaccharides could be assigned from the sample. Fragmentation was shown to yield mostly reducing end sequence fragments (Z(i) and Y(i)), enabling primary sequence assignment. Specific fragmentation pathways or patterns were also detected giving specific linkage information. The reducing end core (Gal/GlcNAcbeta1-3GalNAcol or Gal/GlcNAcbeta1-3(GlcNAcbeta1-6)GalNAcol) could be deduced from the pronounced glycosidic C-3 cleavage and A(i) type cleavages of the reducing end GalNAcol, together with the non reducing end fragment from the loss of a single substituted GalNAcol. Substitution patterns on GlcNAc residues were also found, indicative for C-4 substitution ((0,2)A(i) - H(2)O cleavage) and disubstitution of C-3 and C-4 (Z(i)/Z(i) cleavages). This kind of fragmentation can be used for assigning the mode of chain elongation (Galbeta1-3/4GlcNAcbeta1-) and identification of Lewis type antigens like Lewis a/x and Lewis b/y on O-linked oligosaccharides. In essence, negative ion LC-MS(2) was able to generate extensive data for understanding the overall glycosylation pattern of a sample, especially when only a limited amount of material is available.     

Bis(cyclopentadienyl)methan-verbrückte Zweikernkomplexe,V. Heteronukleare Co/Rh-, Co/Ir-, Rh/Ir- und Ti/Ir-Komplexe mit dem Bis(cyclopentadienyl)methan-Dianion als Brückenliganden

Bis(cyclopentadienyl)methane-bridged Dinuclear Complexes, V^[1]. – Heteronuclear Co/Rh-, Co/Ir-, Rh/Ir-, and Ti/Ir Complexes with the Bis(cyclopentadienyl)methane Dianion as Bridging Ligand^* The lithium and sodium salts of the [C₅H₅CH₂C₅H₄]^- anion, 1 and 2 , react with [Co(CO)₄I], [Rh(CO)₂Cl]₂, and [Ir(CO)₃Cl]n to give predominantly the mononuclear complexes [(C₅H₅-CH₂C₅H₄)M(CO)₂] ( 3, 5, 7 ) together with small amounts of the dinuclear compounds [CH₂(C₅H₄)₂][M(CO)₂]₂ ( 4, 6, 8 ). The ¹H- and ¹³C-NMR spectra of 3, 5 , and 7 prove that the CH₂C₅H₅ substituent is linked to the π-bonded ring in two isomeric forms. Metalation of 5 and 7 with nBuLi affords the lithiated derivatives 9 and 10 from which on reaction with [Co(CO)₄I], [Rh(CO)₂Cl]₂, and [C₅H₅TiCl₃] the heteronuclear complexes [CH₂(C₅H₄)₂][M(CO)₂][M′(CO)₂] ( 11–13 ) and [CH₂(C₅H₄)₂]-[Ir(CO)₂][C₅H₅TiCl₂] ( 17 ) are obtained. Photolysis of 11 and 12 leads almost quantitatively to the formation of the CO-bridged compounds [CH₂(C₅H₄)₂][M(CO)(μ-CO)M′(CO)] ( 14, 15 ). According to an X-ray crystal structure analysis the Co/Rh complex 14 is isostructural to [CH₂(C₅H₄)₂][Rh₂(CO)₂(μ-CO)] ( 16 ).     

Graft polymers with macromonomers. II. Copolymerization kinetics of methacrylate-terminated polystyrene and predicted graft copolymer structures

Copolymerization studies of methacrylate-terminated polystyrene macromonomers (M₁) with several comonomers (M₂) verified the modified kinetic scheme and permitted prediction of graft polymer compositions and structures. Instantaneous and cumulative copolymer compositions, average graft distributions, and grafts per molecule are predicted from FORTRAN IV or BASIC programs. The r₂ relative reactivity ratios determined from styrene copolymerization (0.61) or from low conversion acrylic monomer in aqueous suspension (～0.4) had good agreement with literature values (about 0.6 and 0.4, respectively). Decreased macromonomer reactivity determined at high acrylic monomer conversions was attributed to phase separation phenomena. The Macromers also exhibited lower reactivity than predicted when copolymerized with acrylic monomers in DMSO/benzene solutions (r₂ ～ 0.8).     

Ansamycine, 5. Mitt., Chemie der Metacycloprodigiosine

In order to obtain a better partition of a prodigiosin derivative in biological media, two hydroxy groups were introduced into theansa-part of the molecule. The synthesis of the title compound is described in detail.     

Das Reaktionsverhalten von Cp2NbCl2 gegenüber WF6—Struktur von [Cp2NbCl2]4[WF6]2[WCl6]

The oxidation of Cp₂NbCl₂ with pure WF₆ in SO₂ solution yielded the cationic metallocene species [Cp₂NbCl₂]⁺[WF₆]⁻ essentially in quantitative yield. The same reaction carried out in the presence of either equimolar amounts or a two-fold excess of HCN led to the preparation of the new niobocenium salt [Cp₂NbCl₂]₄⁺[WF₆]²⁻ which was studied by single crystal X-ray diffraction. This compound represents the first example of a structurally characterized metallocene-WF₆⁻ complex, and crystallizes in the tetragonal system: space group, P4₁2₁2(No. 92), a = 11.083(8) Å, c = 48.285 (9) Å; Z = 8; R = 0.0759, R_W = 0.0841. ab]Die Oxidation von Cp₂NbCl₂ mit reinem WF₆ führt in SO₂-Lösung zur Synthese von [Cp₂NbCl₂ ]⁺[WF₆]⁻ in nahezu quantitativer Ausbeute. Die analoge Reaktion führt unter Anwesenheit der äquimolaren Menge oder eines zweifachen Überschusses an HCN zur Ausbildung des Niobocenium-Komplexsalzes [Cp₂NbCl₂]₄⁺ [WF₆]₂⁻[WCl₆]²⁻, von dem eine Röntgenstrukturanalyse angefertigt wurde. Diese Verbindung repräsentiert den ersten structurell charakterisierten Vertreter eines Metallocen-WF₆⁻-Komplexes und kristallisiert im tetragonalen System: Raumgruppe P4₁2₁2 (Nr. 92), a = 11.083(8) Å, c = 48.285(9) Å; Z = 8; R = 0.0759, R_W = 0.0841. kw]Niobium; X-ray diffraction; Oxidation; Metallocenes