Synthesis of 3-methoxyazetidines via an aziridine to azetidine rearrangement and theoretical rationalization of the reaction mechanism

The synthetic utility of N-alkylidene-(2,3-dibromo-2-methylpropyl)amines and N-(2,3-dibromo-2-methylpropylidene)benzylamines was demonstrated by the unexpected synthesis of 3-methoxy-3-methylazetidines upon treatment with sodium borohydride in methanol under reflux through a rare aziridine to azetidine rearrangement. These findings stand in contrast to the known reactivity of the closely related N-alkylidene-(2,3-dibromopropyl)amines, which are easily converted into 2-(bromomethyl)aziridines under the same reaction conditions. A thorough insight into the reaction mechanism was provided by both experimental study and theoretical rationalization.     

Raman Analysis of Polymerization of APST Molecule

In this work we investigated the solidification of aminopropylsilanetriol dissolved in water (∼25%) under different conditions by Raman spectroscopy. The solidification was carried out at three different temperatures 8 °C, 23 °C and 60 °C. The influence of electromagnetic radiation on the polymerization process was also studied. Samples were held to solidify in dark and at UV (254 nm and 356nm) spectral range. In order to investigate the influence of the substrate on the resulting polymer structure, teflon, PVC, glass, brass and silica were used. Best ordered polymerized structure was achieved for samples deposited on plastics and solidified in dark, at room temperature.     

Coulometric redox titrations of hydrazine,phenylhydrazine and isoniazid with electrogenerated lead(IV) acetate and manganese(III) acetate in acetic acid

Summary The conditions fox coulometric determination of small quantities of hydrazine, phenylhydrazine and isoniazid in glacial acetic acid with electrogenerated manganese(III) acetate and lead(IV) acetate were investigated. With the direct coulometric method at room temperature, good results were obtained in the determination of hydrazine and isoniazid with lead(IV) acetate and in the determination of phenylhydrazine with manganese(III) acetate. Hydrazine and isoniazid can also be determined by the coulometric back-titration method if the oxidation with manganese(III) acetate is performed at elevated temperature.

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Zusammenfassung Die Bedingungen für die coulometrische Bestimmung kleiner Mengen Hydrazin, Phenylhydrazin und Isoniazid mit elektrolytisch erzeugtem Mangan(III)-Acetat und Blei(IV)-Acetat in Eisessig wurden untersucht. Bei Zimmertemperatur wurden gute Resultate durch direkte coulometrische Titration des Hydrazins und Isoniazids mit Blei(IV)-Acetat und bei Titration des Phenylhydrazins mit Mangan(III)-Acetat erhalten. Durch coulometrische Rücktitration können bei höheren Temperaturen Hydrazin und Isoniazid mit Mangan(III)-Acetat erfolgreich bestimmt werden.

     

Stereochemistry of cyclic ether formation—II : Intramolecular cyclisation of secondary aliphatic alcohols to tetrahydrofuran-type ethers

The mechanism and stereochemistry of δ-C atom functionalisation in the reactions of secondary straight-chain aliphatic alcohols with lead tetraacetate, ceric ammonium nitrate, and heavy metal (Pb⁴⁺, Hg²⁺, Ag⁺) salts (AcO)^?1, O^2?, CO₃^2?-halogen (I₂, Br₂, Cl₂) combinations are discussed. By demonstrating the intermediacy of 5-bromo-2-hexanol, it was confirmed that the dark silver oxidebromine induced cyclisation of 2-hexanol (and alcohols in general) involves (as the other hypohalite reactions) intramolecular 1,5-hydrogen abstraction by alkoxy radicals and formation of δ-bromohydrins. A novel and simple procedure for obtaining tetrahydrofurans from alcohols by way of the hypochlorite reaction, using silver or mercuric salts and chlorine, is described.     

Potentiometric determination of the protonation constants of 1,3-propanediamine-N,N'-diacetate-N,N'-di-3-propionate

The protonation constants of 1,3-propanediamine-N,N'-diacetate-N,N'-di-3-propionate (1,3-pddadp) were determined in sodium nitrate solution of various concentrations and in 0.1M potassium nitrate medium. The values of the thermodynamic functions (DeltaG, DeltaH and DeltaS) for the successive protonation equilibria, in 0.1M (Na)NO(3) medium, at 25 degrees , are also reported.     

On the characterization of local aromatic properties in benzenoid hydrocarbons

A generalization of the Kekulé index for composite valence structures provides a quantitative value corresponding to Clar's assessment of benzenoid character of aromatic ring systems. The idea involved is further specialized for the individual local rings in the molecules. Comparison with limited experimental data supports the validity of this approach.     

Basicity of nitropyrazoles and their simultaneous spectrophotometric determination

The protonation constants of some 1-, 3(5)-, 3-, 4- and 5-nitropyrazoles have been determined, and compared with those of nitroimidazoles. The effect of the position of the nitro group in the pyrazole and imidazole ring is discussed. The ortho effects of the nitro group in pyrazole and imidazole are compared and found to have identical values. The effect of the nitro group on protonation constants is greater when the nitro group is close to the pyridine nitrogen atom. This, together with the ability of N-unsubstituted nitropyrazoles to dissociate to give nitropyrazole anions, with an accompanying shift of the spectra to longer wavelengths, permits the simultaneous spectrophotometric determination of nitropyrazoles.     

Infrared spectroscopic evidence for Π back-bonding in molecular adducts of pyridine

The observation of the dependence of the in-phase, out-of-plane CH bending on π electron density in aromatics made by Kross was applied to pyridine molecular complexes. Comparison of systems with and without possible back bonding and the existence of a series resembling the Irving-Williams' series, assert the π back bonding to be responsible for the behaviour of the pyridine “umbrella” band.     

Die Zersetzung des Hexacyanoferrates(II) in der Analyse. III

Zusammenfassung Silberionen wirken katalytisch auf die Zersetzung des Hexacyanoferrates(II); in Gegenwart von 2,2-Dipyridyl entsteht als Reaktionsprodukt ein intensiv gefärbter Eisen(II)-Dipyridylkomplex. Bei erhöhter Temperatur und in schwach saurem Medium ist die Wirkung des Silbers sehr stark.Dieser katalytische Effekt wurde für die photometrische Silber-bestimmung verwendet. Der Einfluß der Versuchsbedingungen wurde photometrisch verfolgt und daraus die optimalen Bedingungen abgeleitet. Die Methode ist sehr empfindlich und ermöglicht die Bestimmung von Submikrogrammengen Silber. Die Extinktion wurde mit grünem Filter (oder spektralphotometrisch bei 522 nm) gemessen. Die Eichkurve ist schwach gekrümmt und umfaßt das Konzentrationsbereich von 2 · 10^–7 bis 2· 10^–6 M AgNO₃/l. Bei Einhaltung der genauen Arbeitsbedingungen sind die Resultate innerhalb der Fehlergrenzen photometrischer Bestimmungen reproduzierbar.

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Summary Silver ions have a catalytic action on the decomposition of hexacyano-ferrate(II); in the presence of 2,2-dipyridyl, the reaction product is an intensively colored iron(II)-dipyridyl complex. The action of the silver is very marked at elevated temperatures and in a weakly acid medium.This catalytic effect was employed, for the photometric determination of silver. The influence of the experimental conditions was followed photometrically and the optimal conditions were derived from these findings. The method is very sensitive and permits the determination of submicrogram amounts of silver. The extinction was measured with a green filter (or spectrophotometrically at 522 nm). The calibration curve is slightly bent and includes the concentration range from 2 · 10^–7 to 2 · 10^–6 M AgNO₃ per liter. If the working conditions are strictly maintained, the results are reproducible within the limits of error of photometric determinations.

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Résumé Les ions argent ont une action catalytique sur la décomposition du ferrocyanure; en présence du dipyridyle-2,2, il se forme, comme produit de réaction, un complexe dipyridyle-fer-II, intensément coloré. A température plus élevée et en milieu faiblement acide, l'action de l'argent est très forte.On a appliqué cet effet catalytique au dosage photométrique de l'argent. On a suivi, par photométrie, l'influence des conditions expérimentales et l'on a déduit de ces données les conditions optimales. La méthode est très sensible et permet le,dosage de quantités d'argent submicro. On a mesuré l'extinction avec un filtre vert (ou spectrophotométriquement à 522 nm). La courbe d'étalonnage présente une faible courbure et englobe le domaine de concentration de 2 · 10^–7 à 2 · 10^–6 M AgNO₃/l. Si l'on observe les conditions précises du mode opératoire, les résultats sont reproductibles dans les limites d'erreurs des dosages photométriques.

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II. Croat. Chem. Acta; im Druck.     

Coulometrische Wismutometrie

Zusammenfassung Durch elektrolytische Oxydation einer Bi-Anode in gesättigter NaCl-Lösung können Bi³⁺-Ionen in Lösung gebracht werden. Dieser Prozeß ermöglicht die coulometrische Bestimmung anwesender Anionen, die schwerlösliche Bi-Verbindungen bilden.Es wurden Semimikro- und Mikrobestimmungen von Phosphationen durch elektrolytisch erzeugte Bi³⁺-Ionen bei konstanter Stromstärke ausgeführt. Die Endpunktbestimmung erfolgte amperometrisch bei konstantem Potential mit einer Indikatorelektrode — tropfende Quecksilberelektrode — und mit einer gesättigten Kalomelelektrode als Bezugselektrode. Die coulometrische Wismutometrie bietet eine weitere Möglichkeit der coulometrischen Eichung volumetrischer Lösungen im Sinne des seinerzeitigen Vorschlags vonTutundi.

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Summary Bi³⁺ ions can be brought into solution through electrolytic oxidation of a Bi-anode in saturated NaCl solution. This process makes possible the coulometric determination of the anions present that yield difficulty soluble bismuth compounds.Semimicro- and micro-determinations of phosphate ions were made via Bi³⁺-ions produced electrolytically at constant current strength. The endpoint was determined amperometrically at constant potential with an indicator electrode-dropping mercury electrode-and with a saturated calomel electrode as reference electrode. The coulometric bismuthometry affords a further possibility of the coulometric standardization of volumetric solutions in the sense of the proposal previously advanced byTutundi.

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Résumé On peut utiliser les ions Bi³⁺ en solution par oxydation électrolytique d'une anode en bismuth, en solution de chlorure de sodium saturée. Ce procédé permet le dosage coulométrique des anions présents qui forment des composés peu solubles avec le bismuth.On a mis au point le dosage semimicro et micro des ions phosphates par les ions Bi³⁺ formés électrolytiquement sous intensité constante. On détermine par ampérométrie le point équivalent à potentiel constant à l'aide d'une électrode indicatrice — électrode de mercure à goutte pendante —et avec une électrode au calomel saturée comme électrode de référence. La «bismuthométrie» coulométrique offre de grandes possibilités pour l'étalonnage coulométrique de solutions volumétriques, suivant l'idée queTutundi a émise en son temps.

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Vorgetragen beim Symposium für analytische Chemie in Graz, 29. September bis 1. Oktober 1965.

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Wir danken Herrn Dipl.-Ing.Vladimir Pantovi für seine Hilfe bei unserer experimentellen Arbeit.