Spectral and Thermal Studies of Rare Earth Element 3-methylglutarates

Conditions for the formation of rare earth element (Y, La–Lu) 3-methylglutarates were studied and their quantitative composition and solubilities in water at 293 K were determined (10^–2 mol dm^–3). The IR spectra of the prepared complexes with general formula Ln₂(C₆H₈O₄)₃ nH₂O (n=3–8) were recorded and their thermal decomposition in the air were investigated. During heating the hydrated 3-methylglutarates are dehydrated in one step and next anhydrous complexes decompose to oxides Ln₂O₃ with intermediate formation Ln₂O₂CO₃ (Y, La, Nd–Gd) or directly to the oxides, Ln₂O₃, CeO₂, Pr₆O₁₁ and Tb₄O₇ (Ce, Pr, Tb–Lu). This revised version was published online in August 2006 with corrections to the Cover Date.     

On-column injection onto capillary columns. Part 2: Study of sampling conditions; practical recommendations

During one year continuous use of on-column injection, the typical advantages described in our first report have fully been confirmed. In addition the analysis of large sample volumes has proved promising. Only minor modifications have been applied to the on-column injector device. Broad evidence has been gathered showing that full separation efficiency of the capillary columns after on-column injection is attained only when cold trapping or the solvent effect, as band shortening mechanisms, are working- While, under the conditions of on-column injection, cold trapping is less efficient than with other injection techniques, the opposite holds true for the solvent effect. Compared with splitless injection, the danger of excessive solvent condensation on the column is increased. A working rule is presented for establishing the optimal chromatographic conditions for handling large sample volumes while ensuring full separation efficiency yet avoiding harm to the column.     

Synthesis of thieno[3.2-<Emphasis Type="Italic">b</Emphasis>]pyrrolenine derivatives under the Fischer reaction conditions

The reaction of alkyl 4-(2-acetylhydrazino)-2-methyl-3-thiophenecarboxylates with 3-methylbutan-2-one was carried out under the Fischer reaction conditions. The influence of Lewis acids and solvents on the process was studied. A convenient method for the synthesis of thieno [3.2-b]pyrrolenine derivatives was proposed.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 725–729, March, 2005.     

Chelate mit Diimin- und Thiol-Struktur: Analytische Anwendung der Di-(4-substituierten)-thiosemicarbazone von 1,2- und 1,3-Diketonen

Zusammenfassung In der Gruppe der vierzähnigen Liganden mit Diimin- und Thiolstruktur bilden die Bisthiosemicarbazone von 1,2- und 1,3-Diketonen mit 4-substituierten Thiosemicarbaziden intensiv gefärbte Metallchelate, die für extraktionsphotometrische Bestimmungen in der Spurenanalyse verwendet werden können. Die molaren Extinktionskoeffizienten liegen im Bereich 5000–16000. Die leichte Zugänglichkeit von 4-substituierten Thiosemicarbaziden über die Reaktion von Isothiocyanaten mit Hydrazin bietet eine große Auswahl von Reagentien, besonders für die Flüssig-Chromatographie zur Trennung von komplexen Chelatgemischen.Die Arbeit wurde aus den Mitteln der Deutschen Forschungsgemeinschaft Bonn-Bad Godesberg gefördert.     

The transformations of fluoroalkyl-containing 2-arylhydrazono-1,3-dicarbonyl compounds with methylamine

Fluoroalkylated 1,2,3-triketone 2-arylhydrazones and 2-arylhydrazono-3-oxo esters react variously with methylamine depending on the structure of the fluorinated substituent. 2-Arylhydrazono-1,3-dicarbonyl compounds having “short” fluoroalkyl substituents condense with methylamine at the carbonyl group attached to the non-fluorinated substituent whereas ones containing a lengthy polyfluoroalkyl substituent undergo haloformic cleavage as a result of the amine addition at the carbonyl group bearing such a substituent. The resulting 2-arylazo-3-(N-methyl)amino-1-polyfluoroket-2-en-1-ones and 1-(N-methyl)amino-2-arylhydrazono-3-fluoroalkyl-3-oxopropanamides have complexing properties, and they can bind to nickel(II) and copper(II) ions. Nickel chelates can be obtained by a three-component condensation of 2-arylhydrazono-1,3-dicarbonyl compounds and methylamine in the presence of nickel(II) cations.     

Synthesis and polymerization of N-[N′-(α-methylbenzyl)aminocarbonyl-n-alkyl]maleimide

Two types of optically active N-[N′-(α-methylbenzyl)amino/carbonyl-n-alkyl]maleimides (MBAC) were synthesized from maleic anhydride, 6-amino-n-caproic acid (or 12-amino-n-dodecanoic acid), and (R)-(+)-α-methylbenzylamine. Radical homopolymerizations of MBAC were performed in several solvents at 60 and 110°C for 24 h to give optically active polymers. Radical copolymerizations of MBAC were performed with styrene (ST) and methyl methacrylate (MMA) in dioxane at 60°C. The monomer reactivity ratios and the Alfrey-Price Q-e values were determined. Chiroptical properties of the polymers and copolymers were investigated. © 1995 John Wiley & Sons, Inc.     

Preparation of Y2Ba4Cu7O15-δ Superconductor without High Oxygen Pressure

The synthesis of bulk Y₂Ba₄Cu₇O_15-δ superconductor at atmospheric oxygen pressure via solid state sintering is reported. Temperature ranging from 860 to 890 °C as well as time interval over 2 to 15 days were used to investigate the formation of the Y₂Ba₄Cu₇O_15-δ phase. A time-temperature profile characterizing the conditions for the preparation of Y₂Ba₄Cu₇O_15-δ phase suggests the optimal condition to be sintering at 890 °C for over 10 days. Detailed results of X-ray diffraction, electrical resistivity, iodometric titration and magnetization measurements are described.     

Trifluoroacetic acid: a more effective and efficient reagent for the synthesis of 3-arylmethylene-3,4-dihydro-1H-quinolin-2-ones and 3-arylmethyl-2-amino-quinolines from Baylis-Hillman derivatives via Claisen rearrangement

Trifluoroacetic acid has been discovered to be a highly effective and efficient reagent for the tandem Claisen rearrangement and cyclization reaction to yield 3-arylmethylene-3,4-dihydro-1H-quinolin-2-ones from compounds obtained from the S_N2 reaction between anilines and acetyl derivatives of Baylis-Hillman adducts of acrylates in the presence of DABCO. In contrast, similar compounds obtained from the acetyl derivatives of Baylis-Hillman adduct of acrylonitrile on treatment with trifluoroacetic acid directly furnish 3-arylmethyl-2-amino-quinoline via tandem Claisen rearrangement, cyclization and isomerization.     

Degradation of ²-O-4 lignin model and related compounds by the ascomyceteChrysonilia sitophila (TFB 27441 strain)

Growth of the ascomyceteChrysonilia sitophila during degradation of lignin model dimers and monomers was compared to a glucose control. An inhibition of growth by Cα-carbonyl monomers and stimulation by β-O-4 lignin model and vanillyl alcohol were observed. A comparison of the degradation by this ascomycete with the basidiomycetePhanerochaete chrysosoporium showed similarities in relation to the type of degradation caused.     

Synthesis, electrochemical and biological studies on polyfunctionalized 4-ferrocenyl-4H-pyran and 4-ferrocenyl-1,4-dihydropyridine derivatives

The first synthesis of polyfunctionalized 4-ferrocenyl-4H-pyran and 4-ferrocenyl-1,4-dihydropyridine derivatives, as well as some of their relevant properties, including an electrochemical study and some aspects of their biological profile have been described.