Electron impact induced fragmentation of aromatic N-alkoxy-imines I. Ring closure in (M-CH2O)+• ions by intramolecular aromatic substitution

Summary N-Butoxy- and N-propoxy-imines derived fromo-,m-, andp-substituted benzaldehydes (X = F, Cl, Br, I) decompose upon electron impact to the respective aldoximes by loss of C _n H_2n and competitivelyvia 1,5-distonic radical cations by loss of CH₂O to 1,3-distonic ions which eliminate H and/or a halogen atom in the course of homolytic aromatic substitution, giving rise to cyclic (M-CH₂O-H)⁺ or (M-CH₂O-X )⁺ ions.Dedicated with warm regards to Prof. Dr.D. Seebach, Zürich, on the occasion of his 60^th birthday     

Speed of Sound, Isentropic Compressibilities, and Excess Molar Volumes of Binary Mixtures Containing p-Dioxane

The speed of sound u in and densities of eight binary mixtures of p-dioxane (p-C₄H₈O₂) with methylcyclohexane (c-C₆H₁₁CH₃), 1-chlorohexane (C₆H₁₃C1), 1-bromohexane (C₆H₁₃Br), p-xylene [C₆H₄(CH₃)₂], propylbenzene (C₆H₅C₃H₇), methyl acetate CH₃COOCH₃), butyl acetate (CH₃COOC₄H₉), and amyl acetate (CH₃COOC₅H₁₁) were measured over the whole composition range at 30°C. Isentropic compressibilities (K _S), Rao's molar sound functions (R), excess molar volumes (V ^E), excess isentropic compressibilities (K _S ^E ) together with relative change in volume V/₁₂ values, have been obtained for all measured mole fractions. The excess partial molar volume (V₁-V ₁ ⁰ ) of p-dioxane in different solvents have also been estimated. The experimental results have been analyzed in terms of the Prigogine–Flory–Patterson theory of solutions.     

Synthesis and Characterization of Novel Polyimides Based on Pyridine-containing Diamine

A new aromatic diamine monomer containing pyridine unit, 2,6-bis （4-aminophenoxy- 4＇-benzoyl）pyridine（BABP）, was synthesized in three steps, starting from 2,6-pyridinedicarboxyl chloride. A series of novel pyridine-containing polyimides were prepared v/a the polycondensation of BABP with various aromatic dianhydrides through poly（amic acid） precursors, and thermal or chemical imidization of the precursors. The polyimides exhibit desirable properties, e.g., good solubility in N-methyl-2-pyrrolidone and m-cresol, excellent thermal stability and film-forming capability, as well as high inherent viscosity, indicating high molecular weight.     

Synthesis of Arylidene Derivatives of 1-Aryl-3H-pyrrol-2-ones

The aminolysis of 5-aryl-3-arylidene-3H-furan-2-ones by the action of aromatic amines leads to the formation of substituted amides of 4-oxo acids, the subsequent azacyclization of which in the presence of acetic anhydride leads to the formation of 1,5-diaryl-substituted 3-arylidene-3H-pyrrol-2-ones. The mechanism of the occurring and alternative transformations is discussed.     

Effect of Chamber Gas Phase on Mobile Phase pH and on Separation Efficiency in TLC. A New Mode of Chromatography

A new variant of thin-layer chromatography (TLC), based on a gradual change of mobile phase acidity during elution, is proposed. The pH change occurs in the mobile phase moving along the TLC plate as a result of its contact with an acidic or a basic gas phase that replaces the initial mobile phase vapor in the TLC chamber. The potential of this approach has been demonstrated by using carbon dioxide and ammonia gases to improve the resolution of benzoic acids and aromatic amines on polyamide TLC plates.     

Cyphostemmins A-B, two new antifungal oligostilbenes from Cyphostemma crotalarioides (Vitaceae)

Two new antifungal resveratrol dimers, cyphostemmins A-B (1–2), have isolated from the roots of Cyphostemma crotalarioides planch (Vitaceae) together with resveratrol 3 and previously known reseveratrol dimers (4–7). Structures of these new compounds have been established on the basis of their MS and ¹H and ¹³C NMR spectroscopic data.     

Thermogravimetric properties of inclusion complexes ofβ-cyclodextrin with benzene,acetylsalicylic acid and methyl salicylate

This paper reports TG analyses of inclusion complexes of-cyclodextrin with benzene, acetylsalicylic acid and methyl salicylate. The data were used for calculation of the compositions of the three body complexes and the apparent kinetic parameters of the thermal decompositions. Water exclusion proceeds as a reaction with ordern=1 and an activation energy about 20 kJ/mol. The expulsion of aromatic guest molecules follows ann=1 order process with the activation energy above 155 kJ/mol, except that for the methyl salicylate complex, which was found to be ca. 64 kJ/mol.     

Coupling of thermal desorption in modified closeable sampling columns with wide-bore capillary gas chromatography and mass spectrometric detection

In contrast to usability of Curie-point pyrolysis at 700°C directly attached to gas chromatography-mass spectrometry (GC-MS) for determination of organic wood preservatives in waste wood samples the investigation method reported here consists of thermal desorption at temperatures about 260°C in connection with GC-MS for peak identification or GC with flame ionization detection for quantitative analyses. So-called “modified closeable sampling columns” are used as batch-reactor in thermal desorption experiments. Desorbed vapours can be introduced on capillary columns without sample discrimination and without a disturbing lost of resolution. In this manner a lot of individual polycyclic aromatic hydrocarbons were determinated in waste wood samples, especially in railway sleepers.     

A Sterically Hindered Zirconocene Complex (1,2-Ph2C5H3)2ZrCl2:Synthesis, Structure and Properties as Olefin Polymerization Catalyst

SinceKaminskyeIal.discoveredthehighlyactivezirconocenedich1oride/methyl-aluminoxane(MAO)catalyticsystemforolefinpolymerization',intensiveresearchworkhasbeenfocusedondevelopingnewgroup4metal1ocenecatalystsforimprovingcatalystactivitiesandpolymerproperties"'.Inthedevelopmentofnewmetallocenecatalystsystems,liganddesignandmodificationhaveplayedanimportantrole.lthasbeenknownthatevenminormodificationofagivenligandframeworkcouldresultinsignificantchangesincatalystactivitiesandpolymerproperties'.Int…     

A new method for the synthesis ofN-methylmorpholinium 4-aryl-5-cyano-2-oxo-1,2,3,4-tetrahydropyridine-6-thiolates and their properties

N-Methylmorpholinium 4-aryl-5-cyano-2-oxo-2-oxo-1,2,3,4-tetrahydropyridine-6-thiolates were obtained by the condensation of aromatic aldehydes, cyanothioacetamide, and Meldrum's acid in the presence ofN-methylmorpholine. They were then used in the syntheses of substituted 6-alkylthio-3,4-dihydropyridin-2(1H)-ones and 4,5-dihydrothieno[2,3-b]pyridin-6(7H)-ones. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1852–1856, October, 1997.