Search results for "carbon"

Über Segmentlängenverteilung und Lichtabsorption bei Copolymeren aus Methacrylnitril und Acrolein oder Methacrolein. Polymere Acroleine. 31. Mitt.

1964

Copolymere aus Methacrylnitril und Acrolein oder Methacrolein werden hinsichtlich der Absorption der Carbonylgruppe im Ultravioletten und Infraroten untersucht. Zur Beschreibung des Absorptionsverhaltens wird die statistische Theorie von ALFREY und GOLDFINGER uber die Segmentlangenverteilung in copolymeren benutzt. Es ergibt sich, das im wesentlichen die isoliert stehenden Aldehydgrundbausteine einen Beitrag zur Carbonyl-absorption liefern. Bei Sequenzen aus zwei und drei Aldehydgrundbausteinen reagieren die Carbonylgruppen zu cyclischen Aldehydhydratathern, wahrend bei langeren Sequenzen ungefahr 20% der Carbonylgruppen nicht cyclisieren. Copolymers from methacrylnitrile and acrolein or me…

Sensitive and selective determination of metabolically formed trans -dihydrodiols and phenols of benzo[ a ]pyrene in water and urine samples by HPLC …

1998

A method has been developed to separate hydroxylated metabolites of the carcinogenic polycyclic aromatic hydrocarbon benzo[a]pyrene, i. e. trans-4,5-, 7,8-, 9,10-dihydrodiol and 1-, 3-, 7-, and 9-phenol, by HPLC with amperometric detection employing an isocratic methanol/water eluent (70:30, v/v) containing 0.5 g/L sulfuric acid and 1 g/L lithium perchlorate. Compared with the usually applied fluorescence (λex = 265 nm, λem = 460 nm) and ultraviolet (λ = 265 nm) detection, the amperometric technique is about 2–12 times more sensitive for the determination of all metabolites investigated. The method was applied to the determination of the seven metabolites of benzo[a]pyrene in different wate…

ChemInform Abstract: Concave π-Prismand Hydrocarbon [2.2.2]Cyclophanes and Their Crystalline Ag-Triflate Complexes.

2010

New small concave hydrocarbon cyclophanes were prepared via the well-known HD-2SO2-method. The cyclophanes obtained are isomers of the very well-known [2.2.2]p,p,p-cyclophane, C24H24, a π-prismand efficiently complexing Ag+-ion. X-ray crystal structure determinations showed the bis-sulfide 7 (1,10-dithia[3.3.2]m,p,p-cyclophane) to be helically chiral and that the conformation of the parent hydrocarbon cyclophane 13 ([2.2.2]m,p,p-cyclophane) does not change dramatically upon complexation with the Ag+-ion. The 16- and 17-membered [2.2.2]m,m,p- and [2.2.2]m,p,p-cyclophane (15 and 16) also act as π-prismands and form surprisingly similar crystalline 1:1 Ag-triflate complexes (π-prismates) as th…

- conformational preference of , -9-oxobicyclo[3.3.1]nonane-2,4-dicarboxylic acid

1985

Abstract The 1 H and 13 C nmr spectra of exo , exo -9-oxobicyclo[3.3.1]nonane-2,4-dicarboxylic acid, 3, in DMSO-d 6 or alkaline D 2 O, clearly show that it exists in a boat - chair -conformation with equatorial carboxyl groups, thus being the first case of boat - chair preference of a bicyclo[3.3.1] nonan-9-one due to the presence of exo , exo -2,4- substituents.

I(py)2BF4, ein neues Reagens: allgemeine Methode für die 1,2-Iodfunktionalisierung von Olefinen

1985

Chemical Carcinogenesis by Polycyclic Aromatic Hydrocarbons

1982

The realization that for a vast number of toxic effects, not the given compound itself was responsible but rather a metabolite that was produced from the compound, brought about an enormous step forward in chemical carcinogenesis and in toxicology in general (1–15). In chemical mutagenesis and in chemical carcinogenesis very often coumpounds, which by themselves are chemically inert, will produce mutagenic and carcinogenic effects. A prime example of this is the polycyclic aromatic hydrocarbons, which consisting of condensed aromatic rings are chemically inert, yet do produce mutagenic and carcinogenic effects. During the last 10 to 20 years researchers have started to realize that this is …

ChemInform Abstract: Sustainable Carbon-Carbon Bond Formation Catalyzed by New Oxamate-Containing Palladium(II) Complexes in Ionic Liquids.

2014

New and versatile bis(oxamato)palladate(II) complexes (I) are synthesized and investigated for both Suzuki and Heck coupling reactions in molten tetra-n-butylammonium bromide as ionic liquid.

Theoretical Study of the Elimination Kinetics of Carboxylic Acid Derivatives in the Gas Phase. Decomposition of 2-Chloropropionic Acid

1997

The reaction mechanism for the decomposition of 2-chloropropionic acid in the gas phase to form hydrogen chloride, carbon monoxide, and acetaldehyde has been theoretically characterized. Analytical gradients have been used by means of AM1 and PM3 semiempirical procedures and ab initio methods at HF and DFT (BLYP) levels with the 6-31G** basis set. The correlation effects were also included by using the perturbational approach at the MP2 level with the 6-31G** and 6-31++G** basis sets and the variational approach at the CISD/6-31G** level and by means of MCSCF wave functions with a (6,6) complete active space and the 6-31G** basis set. The global potential energy surface has been studied, an…

Mammalian Xenobiotic Epoxide Hydrolases

2002

Toward an Understanding of the Mechanisms of the Intramolecular [5 + 2] Cycloaddition Reaction of γ-Pyrones Bearing Tethered Alkenes. A Theoretical S…

2000

The molecular mechanism for the intramolecular [5 + 2] cycloaddition reaction of β-silyloxy-γ-pyrones bearing tethered alkenes has been characterized using ab initio methods. A comparative study for this sort of cycloaddition carried out at different computational levels points out that the B3LYP/6-31G* calculations give similar barriers to those obtained with the MP3/6-31G* level. Analysis of the energetic results shows that the reaction takes place along a stepwise process:  first, the migration of the neighboring silyl group to the carbonyl group of the γ-pyrone takes place to give a weak oxidopyrylium ylide intermediate, which by a subsequent concerted intramolecular [5 + 2] cycloadditi…