Zinkstaubdestillation im Mikrogrammbereich

A method for zinc dust distillation of 20–200 μg of substance under controlled conditions is described. The sample is heated on copper-activated zinc up to 350–450° C for several minutes in a TAS-cartridge. The resulting oxygen-free aromatic resp. the stable heterocyclic components are transferred directly to the starting point of a TLC-plate by a stream of nitrogen at 15 ml/min and identified after chromatography. Thermography is applied to study the reaction process and to determine the optimal temperature ranges. Examples of application to the groups of naphthalene-, anthracene-, phenanthrene-,tetracene- and indol derivatives are listed.     

Sequential convexification in reverse convex and disjunctive programming

This paper is about a property of certain combinatorial structures, called sequential convexifiability, shown by Balas (1974, 1979) to hold for facial disjunctive programs. Sequential convexifiability means that the convex hull of a nonconvex set defined by a collection of constraints can be generated by imposing the constraints one by one, sequentially, and generating each time the convex hull of the resulting set. Here we extend the class of problems considered to disjunctive programs with infinitely many terms, also known as reverse convex programs, and give necessary and sufficient conditions for the solution sets of such problems to be sequentially convexifiable. We point out important classes of problems in addition to facial disjunctive programs (for instance, reverse convex programs with equations only) for which the conditions are always satisfied. Finally, we give examples of disjunctive programs for which the conditions are violated, and so the procedure breaks down.The research underlying this report was supported by Grant ECS-8601660 of The National Science Foundation and Contract N00014-85-K-0198 with the Office of Naval Research. Reproduction in whole or in part is permitted for any purpose of the U.S. Government.On leave from the University of Aarhus, Denmark.     

Mikroanalytische untersuchungen zur Löslichkeit von Naturstoffen in überkritischem Kohlendioxid

The pressure-dependent solubility of some natural products in gaseous carbon dioxide compressed to pressures in the range 80–2000 bar has been examined with the help of a micro-extraction apparatus. The solubilities vary greatly from one compound to another, but always increase with pressure. There is a linear relationship between the logarithms of the solubility and of the density of the compressed gas. Besides pressure, the temperature also influences the solubility in carbon dioxide.     

Synthesis of CdSe nanoparticles in the presence of aminodextran as stabilizing and capping agent

Water-dispersible Amdex-CdSe nanoparticle complexes with sufficient luminescence intensity were prepared at room temperature by rapidly mixing aqueous solutions of either sodium selenide or selenourea with those of cadmium chloride in the presence of amino-derivatized polysaccharides (Amdex) as stabilizing agent. It was shown that the size of CdSe crystallites decreased with increasing content of the polymer in the precipitation process. When present in a sufficient amount, Amdex was found to be an effective stabilizing and capping agent, producing CdSe nanocrystals of weak-to-medium luminescence intensity (maximum room temperature quantum yields of 15-16%). Furthermore, Amdex has proven to be an effective protective agent against photochemical degradation.     

Interaction of silver halides with gelatin of like charge

Summary Interactions of gelatin with silver bromide and silver iodide sols of like charges have been studied as a function of gelatin concentration, pH, and addition of neutral electrolytes. Silver halide solsin statu nascendi and aged sols were used in the experiments. Solsin statu nascendi showed a scattering intensity maximum indicating coagulation, while aged sols did not. At higher pH values, the maximum appeared, if sufficient amounts of electrolyte and gelatin were present. It is suggested that gelatin reduces the effective surface charge density of the colloidal particles. Such silver halide sols of reduced charge are then coagulated by smaller amounts of electrolytes than the same sols in the absence of gelatin. For very large concentrations of gelatin, close to the gel point, coagulation occurred wheter sols were aged orin statu nascendi.

---

Zusammenfassung Es wurde die Wechselwirkung zwischen Gelatine und AgBr- bzw. AgJ-Solen gleichen Ladungszeichens in Abhängigkeit von der Gelatinekonzentration, dem pH-Wert und der Konzentration an neutralen Elektrolyten untersucht. Zu den Untersuchungen wurden Solein statu nascendi und gealterte Sole verwendet. Bei Solenin statu nascendi trat ein Maximum in der Streuintensität auf, das Koagulationsvorgänge anzeigt; bei gealterten Solen wurde ein derartiges Maximum erst bei höherenPh-Werten beobachtet, wenn ausreichende Mengen an Elektrolyt und Gelatine vorhanden waren. Bei sehr hohen Gelatine-Konzentrationen (im Bereich um den Gelpunkt) tritt die Koagulation sowohl in gealterten wiein statu nascendi-Solen ein.Es wird angenommen, daß die Gelatine die wirksame Oberflächenladungsdichte der kolloidalen Partikel ver-ringert. Derartige Silberhalogenidesole mit verringerter Oberflächenladung werden dann durch geringere Mengen von Elektrolyt ausgefällt als dieselbe Sole bei Abwesenheit von Gelatine.

---

---

With 8 figures

---

Supported by the Federal Water Pollution Control Administration Grant WP-00815 and by the U. S. Army Research Office (Durham), Grant No. DA-ARO (D)-31-124-G 656.

---

Presented at the 153. ACS National Meeting, Miami Beach, Florida, April 1967.

---

Part of the M. S. Thesis byR. Nemeth     

Synthesis, neutron structure, and reactivity of the bis(dihydrogen) complex RuH2(eta(2)-H2)2(PCyp3)2 stabilized by two tricyclopentylphosphines

Treatment of Ru(eta4-C8H12)(eta6-C8H10) with 3 bar H2 in the presence of 2 equiv of tricyclopentylphosphine (PCyp3) in pentane resulted in the isolation of the new bis(dihydrogen) complex RuH2(eta2-H2)2(PCyp3)2 (2), characterized by NMR and single-crystal X-ray and neutron diffraction. The single-crystal neutron diffraction study is the first carried out for a bis(dihydrogen) complex. The coordination geometry around the metal center is a distorted octahedron defined by the two phosphines in a trans configuration (making an angle of 168.9(1) degrees ), two cis dihydrogen ligands, and two hydrides trans to them, defining the equatorial plane. The H-H bond distances (0.825(8) and 0.835(8) A) are characteristic of two "unstretched" dihydrogen ligands. H/D exchange between the Ru-H and the C-D bonds of deuterated benzene is observed within 1 h, leading to the formation of various isotopomers RuHxD6-x(PCyp3)2 (with x = 0-6). 2 is a catalyst precursor for ethylene coupling (20 bar, 293 K) to a functionalized arene (Murai reaction). We found a 90% conversion of acetophenone to 2-ethylacetophenone within 35 min, whereas 10 h was needed in the same conditions using the analogous tricyclohexylphosphine complex, RuH2(eta2-H2)2(PCy3)2, the best catalyst precursor, at room temperature, prior to this work.     

Furylvinylhalogenides,XII: Reactions of β-chloro-α-cyano-β-(5-nitrofur-2-yl)-acrylic acid derivatives with malonic acid derivatives

Summary Reactions of -chloro--cyano--(5-nitrofur-2-yl)-acrylic acid derivatives with malonic acid derivatives in the presence of collidine yield the allyl anions3a–d. The pyridines4, 8 or9 are formed by cyclization of3 under acidic conditions. The 2-chloropyridine4a reacts with nucleophiles under substitution. The treatment of ethyl dichloropropionate1b with C-H-acidic compounds provided the cyclopropanes11 or12, the configurations of which were determined by¹³C-NMR spectroscopy. The results of the X-ray structure analysis of8c are discussed.

---

Furylvinylhalogenide, 12. Mitt.: Reaktionen von -Chlor--(5-nitrofur-2-yl)--cyanacrylsäurederivaten mit Malonsäurederivaten

Zusammenfassung Die Umsetzung von -Chlor--cyan--(5-nitrofur-2-yl)-acrylsäurederivaten mit Malonsäurederivaten in Gegenwart von Collidin führt zu Allylanionen3a–d. Unter sauren Bedingungen cyclisiert3 zu den Pyridinen4, 8 oder9. Das 2-Chlorpyridin4a reagiert mit Nukleophilen unter Substitution. Setzt man den Dichlorpropionsäureester1b mit C-H-aciden Verbindungen in Gegenwart von Collidin um, so werden die Cyclopropane11 bzw.12 gebildet, deren Konfigurationen mit Hilfe der¹³C-NMR-Spektroskopie bestimmt wurden. Die Ergebnisse der Röntgenkristallstrukturanalyse von8c werden diskutiert.