Easy α- to β-migration of an enol moiety on a pyrrole ring

Functionalized pyrrolic enols, 2-(2,2-dicyano-1-hydroxyethenyl)-1-methylpyrroles, synthesized from 2-ethenylpyrroles by a nucleophilic SEt-OH exchange, upon heating (75-142 °C) are readily rearranged to their 3-isomers in near to quantitative yield. The inter or intramolecular auto-protonation of a pyrrole ring by the acidic enol hydroxyl to form a mesomeric pyrrolium cation or zwitterion is suggested to be a key step in the rearrangement.     

Die untersuchung von adsorptionsgleichgewichten auf graphitiertem thermischen ruß mittels gas-chromatographie

Zusammenfassung Auf der Oberfl?chevon graphitiertem themischen Ru? werden im Grenzgebiet kleiner Belegungen die Retentionsvolumina und Adsorptionsw?rmen der Alkane, Alkene, Alkadiene, Alkine, Cyclane,Cyclene von C₁−C₆ und Benzol bestimmt. Es werden die Abh?ngigkeiten der Adsorptionsw?rmen dieser Moleküle von ihren Polarisierbarkeiten Zhal der Kohlenstoffatome, Grad der Verzweigung und Cyclisierung, Anwesenheit von Doppelbindungen und konjugierten Bindungen untersucht.

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Gas chromatographic investigation of the adsorption equilibrium on graphitized thermal carbon black I. The henry-constants and heats of adsorption of C₁−C₆ hydrocarbons at zero coverage

Summary The retention volumes and heats of adsorption at low surface coverages of graphitized thermal carbon black for C₁−C₆ alkanes, alkenes, alkadienes, alkynes, cyclanes, cyclenes, and benzene have been determined. The dependence of heats of adsorption of these molecules on polarisability, carbon number, isomerisation and cyclisation, the presence of double bonds and conjugated bonds were investigated.

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Etude par la chromatographie en phase gazeuse de l'équilibre d'adsorption sur le noir de carbone graphitisé par voie thermique I. constante de henry et enthalpie d'adsorption des hydrocarbures en C₁ à C₆ pour les taux de recouvrement nuls

Résumé On a déterminé les volumes de retention et les enthalpies d'adsorption des molécules d'alcanes, alcènes, alcadiènes, alcynes, cyclanes, cyclènes en C_` à C₆ et du benzène sur la surface du noir de carbone graphitisé par voie thermique pour les taux de recouvrement faibles. On a aussi étudié la relation entre les enthalpies d'adsorption de ces molécules et leur polarisabilité, leur nombre d'atomes de carbone, la ramification de leur cha?ne, la cyclisation, le nombre de doubles liaisons et de doubles liaisons conjuguées.

     

Electrical resistance and thermophysical properties of solid solutions of germanium in iron

Temperature dependence of thermal diffusivity, thermal conductivity, and electrical resistance is studied in solid solutions of germanium in iron at impurity concentrations of 0.49–18.0 at.% Ge over the temperature range 300–1300K. The results obtained are evaluated and compared to similar dependences for the system Fe-Si.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 36–41, June, 1984.     

Dibenzodiazepines in reactions of 2-acetyl-dimedone with 3,4-diaminobenzophenone

The reactions of 2-acetyldimedone and 2-acetyl-3-methoxy-5,5-dimethylcyclohex-2-en-1-one with 3,4-diaminobenzophenoneproduce2-[1-(2-amino-5-benzoylphenyl)amino]ethylidene-5,5-dimethyl-1,3-cyclohexanedioneand 2-acetyl-3-(2-amino-5-benzoylphenyl)amino-5,5-dimethylcyclohex-2-en-1-one, which are cyclized by the action of hydrochloric acid, yielding the respective hydrochlorides of 8-benzoyl- and 7-benzoyl-3,3,11-trimethyl-2,3,4,5-tetrahydro-1H-dibenzo[b,e][1,4]diazepin-2-ones. Hydrolytic cleavage of the 8-benzoyl derivative leads to 2-acetyl-3-(2-amino-4-benzoylphenyl)amino-5,5-dimethylcyclohex-2-en-1-one. A similar cleavage to form 2-acetyl-3-(2-aminophenyl)amino-5,5-dimethylcyclohex-2-en-1-one is observed for the known hydrochloride of 3,3,11-trimethyl-2,3,4,5-tetrahydro-1H-dibenzo[b,e][1,4]diazepin-2-one. The structures of the products were confirmed by PMR spectra and x-ray diffraction data.Riga Technical University, Riga LV-1658. Latvian Institute of Organic Chemistry, Riga LV-1006. University of Cincinnati, Ohio, USA. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 379–391, March, 1997.     

Formation of trichlorophosphazopentafluorophenyl from pentafluoroaniline and its trihaloacetyl derivatives

Conclusions In contrast to the unfluorinated anilides, the trifluoro- and trichloroacetyl derivatives of pentafluoroaniline form trichlorophosphazopentafluorobenzene when treated with PCl₅. The same compound was obtained by the reaction of pentafluoroaniline with PCl₅.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2635–2637, November, 1978.     

REACTION OF LITHIUM DERIVATIVE OF DIETHYL PHENYLMETHANE-PHOSPHONATE WITH KETONES

Abstract

The reaction of the lithium derivative of diethyl ester of phenylmethanephosphonic acid (1-Li) with alkanones, cycloalkanones, alkylaryl and diarylketones 2s-b is studied at -70°C in THF. The corresponding adducts-diethyl esters of l-phenyl-2,2-dialkyl(phenyl)-2-hydroxyethanephosphonic acids 3s-h are isolated, their yields being usually higher at short reaction time. The olefination of 3-Li as well as of 3 (both by thermolysis or in acidic media) proceeds in low degree, while in the case of 3-Na the yields of alkenes 4 are good. The relative configurations of 3b. 31 and 3g are determined by IR and NMR-spectra, as well as by their stereospecific olefination. “Threo”-stereoselectivity of the addition stage of the reaction of 1-Li with 2b, 21 and 2g is observed, the “threo”/“erythro” ratio remaining independent on the reaction time.     

A phenomenological model for hydrocarbon high-temperature autoignition

A four-step phenomenological chemical–kinetic model is presented that is believed to apply to many aspects of combustion of most hydrocarbons at temperatures above about 1000 K. The mechanism involves chain initiation through reactive collision of fuel and oxidizer molecules, fuel consumption in a step that removes radicals, oxidizer consumption in a step that produces radicals and a chain termination step. An expression for the autoignition time is derived on the basis of this model and is applied to describe the ignition of propane–air mixtures and a few other hydrocarbons. It is shown that excellent agreement with ignition times obtained from detailed chemistry can be achieved by this model.