Synthese von 4H-Pyrano[2,3-d]pyrimidinen

Summary Good yields of substituted 5-(5R-2-furyl)-4H-pyrano[2,3-d]pyrimidines4 were obtained in the reaction of 2-ethoxymethyleneamino-3-cyano-4H-pyranes2 with ammonia. Compounds2 were prepared by the condensation of the starting 2-amino-5-acetyl-3-cyano-6-methyl-4H-pyranes1 with ethyl orthoformate. Spectral properties of the bicyclic system4 in relation to compounds3 are discussed.

     

The solid-phase synthesis of 2-5-linked oligoriboadenylates containing 8-bromoadenine

To increase the accessibility of 8-bromo-2′,5′-oligoadenylates, we developed a synthesis of 2′-5′-linked oligoriboadenylates containing varying numbers of 8-bromoadenosine residues based on the use of a CPG-LCA solid support and the phosphoramidite approach. Although N⁶benzoyl protection was satisfactory for incorporation of nonmodified adenine residues into 2′,5′-oligonucleotides, the effective incorporation of 8-bromoadenine into such 2′,5′-linked oligomers required use of a non acyl protecting group. Amidine protection of the purine exocyclic amino function proved compatible with all aspects of the phophoramidite approach and with the hydroxyl protection groups employed.     

Über Reaktionen von Nitrosophenolen, 3. Mitt.: Reaktion von 2-Nitroso-1-naphthol mit Resorcin und Orcin

Zusammenfassung Die Reaktion von 2-Nitroso-1-naphthol mit Resorcin bzw. Orcin in Äther bei Anwesenheit von HNO₃ liefert Benzo[c]phenoxazon-(9) (I), Benzo[c]phenoxazon-(9)-12-oxid (II), Methyl-benzo[c]phenoxazon-(9) (III) sowie 11-Methyl-benzo[c]phenoxazon-(9)-12-oxid (IV). Die Struktur der isolierten Substanzen wurde durch Reduktion mittels TiCl₃ sowie durch die UV- und IR-Spektren gestützt.

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The reaction of 2-nitroso-1-naphthol with resorcinol and orcinol in ether solution in the presence of nitric acid has been studied. From the reaction mixture the benzophenoxazones I–IV have been isolated. Structures were assigned on the grounds of UV and IR spectra and partly by using TiCl₃ as a reducing agent.

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Influence of Coriolis coupling on inelastic scattering of deuterons

Influence of Coriolis coupling on excitation of some Nilsson states in¹⁵⁵Gd,¹⁵⁷Gd and¹⁶⁷Er by inelastic scattering of 12·1 MeV deuterons is analysed. Expanded Nilsson potential with hexadecapolar deformation is used for the model calculations. Theoretical values of reduced transition probability,B(E2) are compared with experimental ones.     

Gamma radiation from the209Bi(3He, 3nγ)209at reaction

Gamma-radiation from the reactions of 28 MeV and 26 MeV³He-ions on the²⁰⁹Bi target has been studied by means of Ge(Li) detectors. Individual observed prompt -ray transitions have been assigned to the corresponding reactions. The results of previous studies of the²⁰⁹At nucleus have been verified and completed. Two new levels at energies of 640 keV and 1270·5 keV have been introduced. Additionally, 15 new transitions have been observed which could belong to²⁰⁹At. The²⁰⁹At level structure is discussed in terms of nuclear models.     

Effect of molecular weight on synthesis and surface morphology of high-density poly(ethylene glycol) grafted layers

This work describes studying the permanent grafting of carboxylic acid end-functionalized poly(ethylene glycol) methyl ether (PEG) chains of different molecular weights from the melt onto a surface employing poly(glycidyl methacrylate) ultrathin film as an anchoring layer. The grafting led to the synthesis of the complete PEG brushes possessing exceptionally high grafting density. The maximum thickness of the attached PEG films was strongly dependent on the length of the polymer chains being grafted. The maximum grafting efficiency was close to the critical entanglement molecular weight region for PEG. All grafted PEG layers were in the "brush regime", since the distance between grafting sites for the layers was lower than the end-to-end distance for the anchored macromolecules. Scanning probe microscopy revealed that the grafting process led to complete PEG layers with surface smoothness on a nanometric scale. Practically all samples were partly or fully covered with crystalline domains that disappeared when samples were scanned under water. Due to the PEG hydrophilic nature, the surface with the grafted layer exhibited a low (up to 21 degrees ) water contact angle.     

Heterogeneous reactions of solid nickel(II) complexes

The influence of different modes of preparation on the stoichiometry of thermal decomposition of isothiocyanatonickel(II) complexes with ammonia was studied. It was found that the complex Ni(NCS)₂(NH₃)₄ (I) prepared by heterogeneous reaction undergoes decomposition in two steps (–2 NH₃, –2 NH₃), while for complex II, of the same composition but prepared by homogeneous reaction from solution, the decomposition proceeds in three steps (–1 NH₃, –1 NH₃, –2NH₃). Electronic and infrared absorption spectra were used for the study of the spectral properties of the starting complex. It was found that the different stoichiometries of thermal decompositions of complexes I and II do not cause differences in the bonding strength of the ammonia molecules (chemical factor); this effect is rather brought about by physical factors such as different imperfections of the crystal lattice.

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Zusammenfassung Der Einfluß der Herstellung auf die Stöchiometrie der thermischen Zersetzung von Amin-Komplexen des Isothiocyanatonickels wurde studiert. Der Zerfall des Komplexes Ni(NCS)₂(NH₃)₄ (I), hergestellt durch heterogene Reaktion, verlief in zwei Etappen (–2 NH₃, –2 NH₃). Beim selben Komplex (II), hergestellt durch homogene Reaktion in Lösung, wurden jedoch drei Etappen beobachtet (–1 NH₃, –1 NH₃, –2 NH₃). Die Eigenschaften des Ausgangsproduktes wurden durch Elektronen- und IR-Spektroskopie untersucht. Das unterschiedliche thermische Verhalten ist nicht auf eine verschiedene Bindungsstärke der NH₃ Moleküle, sondern auf physikalische Ursachen, wie z. B. Unregelmässigkeiten im Kristallgitter zurückzuführen.

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Résumé On a étudié l'influence des diverses méthodes de préparation sur la stoechiométrie de la réaction de décomposition thermique des complexes de l'isothiocyanate de nickel(II) avec l'ammoniac. On a établi que le complexe Ni(SCN)₂(NH₃)₄, (I), préparé rar réaction hétérogène, subit une décomposition en deux étapes (–2NH₃, –2NH₃), tandis que le complexe (II), de même composition, mais préparé par réaction homogène, à partir de solutions, se décompose en trois étapes (–1NH₃,–1NH₃, –2NH₃). Les propriétés spectrales du complexe initial ont été étudiées par absorption électronique et infrarouge. On a trouvé que les différences de stoechiométrie des réactions de décomposition thermique des complexes (I) et (II) n'apportaient pas de différences entre les énergies de liaison des molécules d'ammoniac (facteur chimique). C'est plutôt à des facteurs physiques, comme les différentes imperfections du réseau cristallin, que cet effet serait dû.

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(II) . , Ni(NCS)₂(NH₃)₄ (I), , (–2NH₃,–2NH₃). , II , , (–1 NH₃,–1 NH₃ –2NH₃). . , I II ( ), , .

     

Radiochemical analysis of90Sr in milk,soil and plants by solvent extraction

A universal and fast method of⁹⁰Sr determination in environmental matrices (raw and dried milk, plants, soils) has been elaborated. Solvent extraction method of daughter⁹⁰Y by tributyl phosphate was used. The method of strontium determination is compatible with determination of other transuranic elements (americium, plutonium) and there is no need to check the chemical yield of strontium.     

Oxygen-flask combustion of accumulated organophosphorus pesticides for monitoring water pollution

A procedure is described for the determination of the total concentration of organophosphorus pesticides in aqueous solution based on conversion of the compounds to orthophosphoric acid by oxygen-flask combustion and spectrophotometric determination as phosphomolybdenum blue. The procedure is particularly sensitive when preceded by efficient and selective accumulation of pesticides. The adsorption of malathion, parathion and phosalone on Amberlite XAD-4 resin from 1 l of 7–36 μM water solutions, followed by combustion of 500 μl of eluate yields of orthophosphoric acid with 90–105% recoveries. The detection limit is ca. 150 ng ml^?1 pesticide in an aqueous sample. Inorganic phosphates and most of some commonly present non-pesticide phosphorus compounds are eliminated from the water sample during the adsorption step. In combination with a test for monitoring traces of cholinesterase inhibitors in surface waters, the determination of the total amount of organophosphorus pesticides as a cumulative parameter offers reliable information on the pollution level of the water environment. Application of such a combined procedure to a pond water from an apple orchard showed good correlation between phosphrus content and the cholinesterase inhibition.