Aggregation effects on evaporation and the air/water interface of dodecyltrimethylammonium hydroxide solutions

 The system dodecyltrimethylammonium hydroxide (DTAOH)–water was studied by surface tension, ion-selective electrodes and evaporation in an electrobalance. Results confirmed earlier conclusions about a stepwise aggregation mechanism in DTAOH solutions. The aggregation process started at a total concentration C _T=(2.51±0.10)×10^-4 mol dm^-3) which probably corresponds to the formation of dimers. At C _T= (1.300±0.041)×10^-3 mol dm^-3 there was a change in the surface and evaporation behavior, corresponding to the formation of small, fully ionized aggregates which grew with increasing concentration. At C _T= (1.108±0.010)×10^-2 mol dm^-3 the formation of true micelles with hydroxide counterions in the Stern layer did not change significantly the evaporation and adsorption behavior. This means that between this concentration and C _T=(3.02±0.28)× M28.8n10^-2 mol dm^-3, the changes in structure were gradual. At the latter concentration there was a sudden change in the monolayer state at the air/water interface, with a strong surfactant desorption, and a major change in evaporation behavior. The changes are compatible with the formation of few, large aggregates reducing the total concentration of kinetically independent solute units, which in turn increased the activity of the solvent. This phenomenon is in agreement with literature information. The reduction in the evaporation rate of water was mainly due to the reduction of the water activity, caused by colligative effects. The reduction of the effective area available for evaporation had only a slight effect in water evaporation. Received: 9 January 1997 Accepted: 19 October 1997     

Umsetzungen von Polyacroleinen mit reaktionsfähigen Polymeren

Zusammenfassung Durch Radikalketten-Polymerisation von Acrolein erhält man Polymere mit Aldehydgruppen. Diese sind zu vielfältigen Umsetzungen befähigt. In dieser Mitteilung werden nur zwei Arten von Reaktionen behandelt; nämlich die Reaktion der Aldehydgruppen untereinander, wobei unter Disproportionierung Polyhydroxypolycarbonsäuren entstehen. DieseCannizzaro-Reaktion tritt auch an der Oberfläche fester Polyacroleine ein. Eingehend behandelt wird die Umsetzung wäßriger Polyacrolein-Lösungen mit anderen Polymeren, welche Amino-, Hydroxyl-oder Mercaptangruppen enthalten. Die Kennzeichen der entstehenden Verbundpolymeren werden beschrieben und mit denWillstätterschen Symplexen verglichen. Auf Beziehungen dieser Reaktionen zu biochemischen Prozessen wird hingewiesen. Ferner wird die Diffusion von Polymeren durch Membranen mit reaktiven Gruppen (Agar-Agar und Gelatine) untersucht. In einigen Fällen tritt eine Oberflächen-Pfropfung ein.19. Mitt, üiber Polymere Acroleine, vorgetragen auf der 20. wissenschaftlichen Arbeitstagung der Kolloid-Gesellschaft vom 19. bis 20. 10. 1961 in Bad Oeynhausen; 18. Mitt, siehe Angew. Chem.72, 771 (1960).Fräulein Dr.Irmela Löflund und Herrn Dr.Mathias Marx, die an diesen Untersuchungen maßgebend beteiligt waren, möchte ich für ihre Mitarbeit herzlich danken. Herrn Prof. Dr.W. Kern, Direktor des Organisch-Chemischen Instituts, danke ich für mannigfache Förderung und anregende Diskussionen. Die Untersuchungen wurden durch Mittel des Fonds der Chemischen Industrie sowie der Firma Degussa, Frankfurt/Main, unterstützt, wofür ebenfalls herzlichst gedankt sei.     

Volumes of activation for the reactions of Pentacyanocobaltate(III) Complexes in aqueous solution

The volumes of activation in cm³ mol^?1 for the aquation of Co(CN)₅X^3? were determined at 40°C and μ = 1 M (NaClO₄) to be + 7.8 ± 0.5 for X = Cl^?, + 7.6 ± 0.6 for X = Br^?, + 14.0 ± 0.7 for X = I^?, and + 16.8 ± 0.5 for X = N₃^? (0.1 M HClO₄), respectively. The volumes of activation for the aquation of Co(CN)₅Cl^3? at μ = 0.1 M are + 10.0 ± 0.6 cm³ mol^?1 and ± 9.1 ± 0.3 cm³ mol^?1 at 40°C and 25°C, respectively. The corresponding values for the anation of Co(CN)₅OH₂^2? (at 40°C) and μ = 1 M by Br^?, I^?, and NCS^? are +8.4 ± 1.0, +9.4 ± 1.6, and +8.2 ± 0.9 cm³ mol^?1, respectively. These data are discussed in terms of a dissociative (D) mechanism.     

Bimetallic complexes from amphoteric group 13/15 ligands: syntheses and X-ray crystal structures

Bimetallic, pentel-bridged complexes of the type [(dmap)Me2M-E(SiMe3)2-M'(CO)n] (M=Al, Ga; E=P, As, Sb; M'=Cr, Fe, Ni; DMAP=4-(dimethylamino)pyridine) are formed by reactions of DMAP-coordinated monomeric Group 13/15 compounds [(dmap)Me2M-E(SiMe3)2] with the transition metal complexes [(Me3N)Cr(CO)5], [Fe3(CO)12], and [Ni(CO)4]. For the first time, this reaction offers a general pathway to compounds containing a Group 13 metal and a transition metal bridged by a pentel atom. Complexes prepared in this way were characterized by IR and multinuclear NMR spectroscopy and by single-crystal X-ray structure analysis. Their electronic and structural properties are discussed in detail. The Group 13/15 ligands are very weak acceptors, which is likely to be due to the electropositive Group 13 metal, and the complexes feature comparatively long pentel-transition metal bonds. In addition, the synthesis and structural characterization of the parent DMAP-coordinated gallanes [(dmap)Me2Ga-E(SiMe3)2] (E=P, As) are reported.     

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     

Improved catalysts for the palladium-catalyzed synthesis of oxindoles by amide alpha-arylation. Rate acceleration, use of aryl chloride substrates, and a new carbene ligand for asymmetric transformations

Catalysts comprised Pd(OAc)(2) and either PCy(3) or sterically hindered N-heterocyclic carbene ligands provide fast rates for a palladium-catalyzed synthesis of oxindoles by amide alpha-arylation. This catalyst system allowed for room-temperature reactions in some cases and reactions of aryl chlorides at 70 degrees C. Most important, reactions occurred in high yields under mild conditions to form the quaternary carbon in alpha,alpha-disubstituted oxindoles. The combined inter- and intramolecular reaction afforded an efficient synthetic method for formation of alpha-aryloxindole derivatives. Surprisingly, catalysts containing tert-butylphosphine ligands, which have been most reactive for ketone arylations, were less active than those containing PCy(3). Use of new, optically active heterocyclic carbene ligands gave substantial enantioselectivity in formation of an alpha,alpha-disubstituted oxindole. In contrast, a variety of optically active phosphine ligands that were tested gave poor enantioselectivity. Mechanistic studies showed that the reaction involves rate-limiting oxidative addition of aryl halide. Base-induced formation of and reductive elimination from an arylpalladium enolate intermediate were both faster than oxidative addition. Deprotonation of the tethered amide appeared to be faster than reductive elimination of the resulting palladium enolate to form the oxindole product.     

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.

---

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