A functional central limit theorem for a nonequilibrium model of interacting particles with unbounded intensity

Under suitable physically reasonable initial assumptions, a functional central limit theorem is obtained for a nonequilibrium model of randomly interacting particles with unbounded jump intensity. This model is related to a nonlinear Boltzmann-type equation.     

Intramolecular diels-alder cycloadditions of bis-diene substrates

Unique internal competition in the intramolecular cycloaddition of bis-diene substrates occurs with high stereoselectivity. Aqueous reaction conditions promote coiling of the lipophilic chain which alters the observed regioselectivity.     

Topological implications of Y-conjugation for electronic transitions of cyanine dyes

To understand connections between electronic transitions of dyes having related conjugated systems, topological arguments from graph theory are often helpful. Using the Chebyshev expansion of the characteristic polynomials of cyanines, it is shown that the two possible structures of tribranched cyanines, i.e., a strongly out-of-plane orientation of one of the conjugated branches or a Y-conjugation of the entire unsaturated system, are both consistent with the similarities between visible absorption of these compounds and of simple chains. To choose between these two structures, evidence from other sources should be added.     

Coulometric titration of organic and pharmaceutical compounds with electrogenerated gold(III)

Summary Electrogenerated AuCl₄– in 0.02M HCl is used to titrate hydroquinone, ascorbic acid, phenylhydrazine, phenelzine sulphate and phenylsemicarbazide, with biamperometric end-point detection. Titration recoveries are reported and compared with results of coulometry with ceric sulphate oxidation. With less than 1 mg of sample, successive titrations can be performed in the same solution, in contrast to coulometry with ceric sulphate. Phenelzine sulphate reacts stoichiometrically, as opposed to its reactions with stronger oxidizing agents.

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Zusammenfassung An der Elektrode entwickeltes AuCl₄– in 0,02M HCl wurde für die Titration von Hydrochinon, Ascorbinsäure, Phenylhydrazin, Phenelzinsulfat und Phenylsemicarbazid mit biamperometrischer Endpunktanzeige verwendet. Die Ergebnisse wurden mitgeteilt und mit den Resultaten der Coulometrie mit Cersulfatoxydation verglichen. Im Gegensatz dazu können mit weniger als 1 mg Probe in derselben Lösung Folgetitrationen durchgeführt werden. Abweichend von seinem Verhalten gegenüber stärkeren Oxydationsmitteln reagiert Phenelzinsulfat stöchiometrisch.

     

Über die NH3-“rocking”-schwinguno in amminmetall komplexen

A magneto-optical investigation of dialkyl derivatives of zinc, cadmium and mercury (in the liquid state, at 20 °C) leads to the conclusion that there is a lack of linearity in such molecules, the largest deviations being observed in the case of the mercury compounds. This shows that the inconsistency of the alteration of any chemical or physical property which is classically observed in the group IIB, is in fact due to mercury and not to cadmium as was often assumed in the literature.     

General and Facile Route to Isomerically Pure Tricyclic Peptides Based on Templated Tandem CLIPS/CuAAC Cyclizations

We report a one‐pot ligation/cyclization technology for the rapid and clean conversion of linear peptides into tricyclic peptides that is based on using tetravalent scaffolds containing two benzyl bromide and two alkyne moieties. These react via CLIPS/CuAAC reactions with cysteines and azides in the peptide. Flexibility in the scaffolds is key to the formation of isomerically pure products as the flexible scaffolds T4 ₁ and T4 ₂ mostly promote the formation of single isomeric tricycles while the rigid scaffolds T4 ₃ and T4 ₄ do not yield clean products. There seems to be no limitation to the number and types of amino acids present as 18 canonical amino acids were successfully implemented. We also observed that azides at the peptide termini and cysteine residues in the center gave better results than compounds with the functional groups placed the other way round.     

Etude dans la série des radicaux hétérocycliques: partie XIV. Radicaux diméthyl-3, 4-isoxazolyl-5. Réactivité en série aromatique et hétéroaromatique: nouvelle voie d'accès à des diméthyl-3, 4-isoxazoles subsitués en C(5) par des groupements aryle et hétéroaryle

The aprotic decomposition of 5-amino-3, 4-dimethyl-isoxazole with excess isoamyl nitrite in aromatic solvents (alkylbenzenes, polyalkylbenzenes, anisole etc.) and in heteroaromatic solvents (thiophene, 2, 4-dimethylthiazole, pyridine, 4-alkylpyridines, dimethyl- and trimethyl-pyridines) leads to 5-aryl- and 5-heteroaryl-isoxazoles in yields of about 40%. This method provides a new way of obtaining 5-iodo-3, 4-dimethyl-isoxazole by the aprotic decomposition of the corresponding amine in the presence of iodine (yield: 30%). The relative reactivity of the 3,4-dimethylisoxazol-5-yl radical in alkyl benzenes, in anisole and in alkylpyridines is very similar to that of other heteroaromatic radicals with the radical site next to a sulfur or an oxygen atom. The radical shows electrophilic character because of the inductive effect of the oxygen atom. In the pyridine series an abnormally high percentage of 2-substitution occurs. This may be explained by a solvatation effect. The characteristic GLC., NMR. and MS. data are reported for most of the compounds studied.     

Synthèse photochimique de biaryles et hétérobiaryles à partir d'aryl-et hétéroarylamines,d'un nitrite d'alkyle et d'un substrat aromatique ou hétéroaromatique

Photochemical synthesis of biaryls and heterobiaryls from aryl and heteroarylamines, alkylnitrite and aromatic or heteromatic substrates The photochemical reaction of aromatic and heteroaromatic amines with excess t-butyl nitrite in aromatic solvents (benzene, p-xylene, mesitylene) and in hetero-aromatic solvents (furan, thiophene) leads to biaryls or heterobiaryls. t-Butyl nitrite is more convenient than isopentyl nitrite which gives by-products. This new method has been used to synthesize 28 compounds in 17 to 60% yield.     

Determination coulometrique d'alcaloides et de sels de bases organiques apres precipitation sous forme de tetraphenylborates

A coulometric microdetermination of salts of certain organic bases and alkaloids is described, based on precipitation as the tetraphenylborates and the coulometric determination of the tetraphenylborate content of the precipitate with electrogenerated silver ion. Eleven compounds were determined with satisfactory accuracy.     

Etude en série triazénique. IV. Synthèse et réactivité d'aryl-3-(diméthyl-3,4-isoxazolyl-5)-1-triazènes et d'arylazo-4-diméthyl-3,4-isoxazolones-5

Synthesis and reactivity of 3-aryl-1-(3,4-dimethyl-5-isoxazolyl)-triazenes and 4-arylazo-3,4-dimethylisoxazol-5-ones According to the experimental conditions and the nature of the substituents on the aromatic ring, aryldiazonium salts react with 5-amino-3,4-dimethylisoxazole ( 3 ) leading to either 3-aryl-1 (3,4-dimethyl-5-isoxazolyl)-triazenes ( 1A ) or 4-arylazo-3,4-dimethylisoxazol-5-ones ( 4 ). Analyses of the products resulting from thermal decomposition of these triazenes in aromatic substrates and in DMSO and their behaviour in acidic medium show that it is essentially the arylazo form 1B which is reactive.