Synthese neuer N-Vinylpyrrole

Syntheses of New N-Vinylpyrroles The reactions of pyrrolyl potassium ( 1 ) with (ethoxymethylene)malonic acid derivatives 2a–e yielded the carbanions 3a–e , which could be hydrolyzed to 4a–e , but with the exception of 4b they were not isolated, because a transformation to the N-vinylpyrroles 5a , c–e by elimination of ethanol took place; 1 reacted with 2b at 80°C to give 4b and 6 . Hydrolysis of 4b with KOH yielded 4g , which eliminated 1 mol of ethanol to form 5f , decarboxylation of which led to N-vinylpyrrole 7 . By cyclization of 5e under various conditions the pyrrolizines 8a , b are obtained, the hydrolysis of which did not give ketone 9 but only amino alcohol 10 . Some other cyclizations of 11a–c and 13 yielded the 3H-pyrrolizine derivatives 12a–c and 14 , respectively.     

Theoretical depolymerization kinetics. IV. Effect of a volatile fraction on the degradation of an initial “most probable” polymer

The effect of volatilization of molecules larger than monomer has been introduced into the solution of the Simha, Wall, and Blatz kinetic equations for the degradation of a high polymer with an initial “most probable” distribution. Equations describing the rate of sample weight and average molecular weight change result. They differ from the previous “most probable” equations primarily in the presence of an additive term representing the random splitting near the chain ends due to bond scission or transfer attack. Equations are also obtained for the rate of formation of each volatile species and hence the product distribution. The effect of volatilization of larger fragments is discussed in detail for the special case of random scission initiation. The product distribution is discussed for two special cases.     

Zur Erklärung einiger Viskositätsanomalien von Solen im Couette-Apparat

Zusammenfassung Es werden zwei Viskositätsanomalien an Gelatine- und Stärkesolen zu erklären versucht, die bei Messungen mit dem Couette gefunden, aber nicht mit Kapülarviskosimetern bisher reproduziert worden sind. Die Erklärung läuft in einem Fall (Gelatinesol) auf die Anahme einer Adsorption des Kolloids am Innenzylinder heraus, die eine Erhöhung der Wandrauhigkeit im hydrodynamischen Sinne und damit eine scheinbare Steigerung der Viskosität zur Folge hat. Die Erklärung des zweiten Falles (Stärkesol) schließt an eine von E. Hatschek für einen Teil der Anomalie bereits gegebene Deutung an, vervollständigt sie aber in einem wesentlichen Punkt. Sie erklärt die Anomalie durch die im Couette während der Messungen selbst erfolgende Zerstörung der Solstruktur bis zum praktischen Verlust der sogen. Strukturviskosität und durch die dann eintretende Strukturturbulenz. Das Stärkesol verhält sich damit ganz analog dem von E. Hatschek und R. S. Jane neuerdings untersuchten Ammoniumoleatsol.Die beiden Anomalien erscheinen bewirkt durch die spezielle Konstruktion des Couette-Apparates. Ihre Nichtreproduzierbarkeit mit Kapillarviskosimetern steht nicht im Widerspruch zu der These des Verfassers, derzufolge alle wesentlichen viskosimetrischen Erscheinungen an kolloiden Systemen mit beiden Apparaturen in gleicher Form gefunden werden.Es wird auf die von der Prandtl'schen Schule studierten Erscheinungen der Wirbelbildung in Grenzschichten und auf die Möglichkeit hingewiesen, daß solche Vorgänge auch im Couette, speziell bei Solen, auftreten und zu Anomalien führen können.     

The electrostatic field of B-DNA

The electrostatic field associated with one complete turn of B-DNA is presented. Two base sequences poly (dG) · poly (dC) and poly (dA) · poly (dT) are studied and the effects of sodium counterions bound to the nucleic acid are investigated. The contrasts between the electrostatic potential and the electrostatic field of the macromolecules are discussed and the possible applications of the field are considered.     

Synthesis of fused polycyclic aromatics by palladium-catalyzed annulation of arynes using 2-halobiaryls

The Pd-catalyzed annulation of arynes by 2-halobiaryls and related vinylic halides provides a very efficient, high yielding synthesis of polycyclic aromatic and heteroaromatic hydrocarbons. This process appears to involve the catalytic, stepwise coupling of two very reactive substrates, an aryne and an organopalladium species, to generate excellent yields of cross-coupled products.     

Determination of the thermodynamic excess functionsG E,H E,andS E of the liquid ternary system AgCl—LiCl—KCl by means of EMF-measurements

By means of EMF-measurements using the formation cell $$graphite/Ag/AgCl(l,x_{AgCl} ) - LiCl(l,x_{LiCl} ) - KCl x_{KCl} /(Cl_2 )graphite$$ the partial molar excessGibbs energies,G _AgCl ^E , of silver chloride in the ternary system AgCl?LiCl?KCl were determined over the whole concentration range at five temperatures between 973 K and 1,123 K. The experimentally determinedG _AgCl ^E -values were fitted using theRedlich-Kister equation. From theRedlich-Kister parameters and their temperature dependence, obtained by the fitting procedure, the integral and partial molar excessGibbs energies, heats of mixing, and excess entropies were calculated. The fitting process permits also the calculation of the thermodynamic excess function of the binary system lithium chloride—potassium chloride.     

Selective excitation effects in microwave optical double resonance and phosphorescence spectroscopy of molecular crystals

The photoexcitation routes used to produce molecular crystal, triplet states are shown to have important optical and microwave spectral consequences. 2-benzoylpyridine crystals at 4.2 K have T₁ → S₀ phosphorescence spectra showing line width dependence on whether initial production of the T₁ state is through direct T₁ → S₀ absorption, or through S₁ ← S₀ absorption followed by S₁ → T₁ intersystem crossing. Striking differences are seen in the optically detected zero-field resonance spectra.     

Amide-water interactions in cosolvent systems. I. Solubilities and apparent molar volumes of methyl paraben

Solubility and apparent molar volume data are used to demonstrate effects of amide alkylation on amide-water interactions at 25° C. Precise measurements were made of the apparent molar volumes of the amides in binary amide-water mixtures using a dilatometric technique. The results show that the apparent molar volumes of alkyl-substituted amides in water pass through a minimum at an amide concentration which varies inversely with the degree of alkylation. Further studies showed that the solubilities of methyl paraben (methyl-p-hydroxybenzoate) and naphthalene in various amide-water solvent systems increased in characteristic fashion with amide alkylation.     

Über die Herstellung von Äther der enantio-14, 15-Dinorlabdan-Reihe aus Eperusäure

The Conversion of Eperuic Acid into Ethers of the enantio-14, 15-Dinorlabdane Series 5 and 6 are strongly odiferous substances of the ambra-type. Their enantiomers 7 and 8 , hitherto unknown, have been synthesized from eperuic acid (4) and their olfactory properties compared with those of 5 and 6 . 4 was esterified by CH₂N₂ and dehydrogenated with (C₆H₅Se)₂/H₂O₂ to the α,β-unsaturated ester 9 (61%). Oxidation by KMnO₄ in acetone yielded the ketone 3 (60%). Epoxidation followed by treatment with acid converted 3 into the acetals 7 (61%) and 8 (14%). 7 and 8 differ from 5 and 6 in odor intensity, and 6 and 8 show slightly different odor quality.     

An investigation of mononuclear and binuclear palladium(II) complexes of egta (egta = glycine,N,N′-(1,2-ethanediylbis(oxy-2,1-ethanediyl)bis[N-carboxymethyl]) by 1H-, 13C- and 15N-n.m.r. methods

1:1 and 2:1 palladium(II) complexes of egta^4– (egta^4– = glycine, N,N-(1,2-ethanediylbis)(oxy-2,1-ethanediyl)bis[N-carboxymethyl]) were prepared by 1:1 and 2:1 addition of K₂PdCl₄ to K₄egta, and examined by ¹H-, ¹³C- and ¹⁵N-n.m.r. methods. The 1:1 complex, [Pd(egta)]^2– in solution, utilizes a square-planar coordination comprised of two nitrogen and two glycinato carboxylate donors of egta^4–, leaving two glycinato carboxylates pendant. The complex has a cis-(R,S) stereochemistry which places both pendant carboxylates below the PdN₂O₂ square plane and the tether backbone of egta^4– in the up, up sense above the same plane. The cis-(R,S) assignment was assisted by computer simulations of the ¹³C-n.m.r. spectrum for four possible isomers. Only cis-(R,S) and trans-(R,R) calculated ¹³C-spectra were compatible with the observed ¹³C-n.m.r. pattern. The HH NOESY spectrum of [Pd(egta)]^2– detects long range coupling of the backbone –OCH₂CH₂O– linkage with both coordinated and pendant glycinato CH₂ moieties. The cis-(R,S) isomer's tortional movements allow such contacts whereas a trans-(R,R) isomer does not. The 2:1 complex, [Pd₂(egta)(H₂O)₂] in solution has an extended-chain structure with each palladium(II) center coordinated in the mer-iminodiacetate-like coordination with two bound glycinato-functionalities.