Search results for "Spectroscopy"

Support effect on the catalytic performance of Au/Co3O4–CeO2 catalysts for CO and CH4 oxidation

2008

Gold-based catalysts supported on Co3O4, on CeO2 and on mixed Co3O4-CeO2 oxides were prepared by co-precipitation. They were tested in the catalytic oxidation of CO and CH4, in separate tests, and their activities were compared with that of the bare oxides. Tests of CH4 oxidation were performed in two consecutive runs in order to evaluate the catalysts stability. The effect of SO2 in the reactant mixture was investigated. The fresh and spent catalysts were analsed by XRD, BET, TPR and XPS techniques. Among the fresh catalysts, Au supported on CeO2 was the most active in CO oxidation whereas Au supported on Co3O4 was the most active for methane total oxidation. Synergy between the two oxides…

Der nachweis der kettenstruktur von aus p-kresol und formaldehyd aufgebauten mehrkernverbindungen. I. Durch verschiedene synthese und identifizierung…

1962

In ubersichtlicher, mehrfacher Synthese werden homologe Mehrkernverbindungen aufgebaut, die aus uber Methylenbrucken verbundenen p-Kresolbausteinen bestehen (Novolak-Struktur). Die verschiedenen, zu einer Mehrkernverbindung fuhrenden Synthesen geben identische Verbindungen. Die Kettenstruktur dieser Mehrkernverbindungen kann durch kettenanaloge Enthalogenierungen, durch geeignete Kondensationen (Gl. (1)) sowie durch entsprechende Substitutionsbanden in den IR-Spektren der Verbindungen nachgewiesen werden. By means of rational, multiple syntheses, homologous polynuclear compounds were prepared, consisting of p-cresol units linked by methylene bridges (Novolac structure). The different ways o…

Synthesis of pyrido[2,3-d]pyrimidines in the reaction of 6-amino-2,3-dihydro-2-thioxo-4(1H)-pyrimidinone with chalcones

1992

6-Amino-2,3-dihydro-2-thioxo-4(1H)-pyrimidinone (1) reacts in boiling DMF with α,/β-unsaturated ketones 2 yielding the pyrido[2,3-d]pyrimidine systems 5 and 6, respectively. The orientation in the addition process can be determined by nmr measurements, especially by NOE difference spectroscopy. The products do not correspond to a normal Skraup or Doebner-v. Miller synthesis.

Silica gel chemistry

1994

A guide for selecting the most appropriate method for ammonium determination in water analysis

2006

Abstract We have critically evaluated the main parameters involved in determining ammonium in water samples, in order to select the most suitable method appropriate to the requirements of the analysis. We compared several methods: reference (ion-selective electrodes, Nessler and indophenol); Roth’s modified; based on luminol reaction; and, based on peroxioxalate reaction.

Conformational study of methyl esters of some aliphaticerythro- andthreo-dichlorocarboxylic acids

1984

The average conformations of methyl esters of some aliphatic erythro- and threo-dichlorocarboxylic acids in dilute carbon tetrachloride solutions have been determined from the vicinal proton–proton coupling constants and 1H NMR shifts. The 13C shift differences between the erythro and threo forms are compared and discussed with regard to the differences in the average conformations.

13C NMR spectroscopic study of diphenyl ether and 28 of its polychlorinated derivatives

1993

The 13 C NMR chemical shifts and coupling constants for diphenyl ether and 28 environmentally interesting polychlorinated diphenyl ethers were measured and analysed

NMR-Spektroskopie an Heterocyclen, 6. Mitt. Favorskii-Umlagerung von α-Brom-β-methoxy-ketonen bei der Imidazol-Cyclisierung in flüssigem Ammoniak

1979

Bei der Imidazolsynthese aus α-Bromketonen und Formiminoethylester in flussigem Ammoniak werden α-alkylsubstituierte Buttersaure-Amide als Nebenprodukte erhalten, deren Entstehen einer Favorskii-Umlagerung zugeschrieben wird. Die isolierten Verbindungen wurden NMR-spektroskopisch untersucht. NMR Spectroscopy of Heterocycles. VI: Favorskii Rearrangement of α-Bromo-β-methoxy Ketones During Imidazole Cyclisation in Liquid Ammonia. During imidazole synthesis with α-bromo ketones and formiminic ethyl ester in liquid ammonia α-alkylbutyric amides were obtained as by-products. Their formation is attributed to a Favorskii rearrangement. The compounds were investigated by NMR spectroscopy.

Effect of S1 Torsional Dynamics on the Time-Resolved Fluorescence Spectra of 9,9‘-Bianthryl in Solution

1997

Time-resolved fluorescence spectra of 9,9‘-bianthryl (BA) were measured in methylcyclohexane (MCH) and a Decalin−isooctane (D−ISOO) mixture at several temperatures between 127 and 200 K. A suitable...

Cyclic Sulfonimidates by Dynamic Diastereomer-Differentiating Cyclisation: Large-Scale Synthesis and Mechanistic Studies

2001

A dynamic diastereomer differentiating cyclisation is the key step in a new large-scale synthesis of both enantiomers of the cyclic sulfonimidates 1 (Aldrich no. 54099-4) and ent-1 (Aldrich no. 54412-4). These are valuable starting materials in the asymmetric synthesis of chiral oxa- and azaheterocyclic compounds. NMR spectroscopic studies on the reacting system reveal N-chloro sulfinamides to be reactive intermediates in the oxidative chlorination of sulfinamides with tert-butyl hypochlorite and allow for the inspection of the configurational behaviour of the involved sulfonimidoyl chlorides and sulfonimidoyl bromides.