Search results for "Epoxide"
showing 10 items of 251 documents
Reaktive Metabolite cancerogener polycyclischer Kohlenwasserstoffe: Synthese und Abfangreaktion von 9-Hydroxybenzo[a]pyren-4,5-oxid
1985
Le compose du titre est prepare a partir de l'acetate-9 de benzo [a] pyrene et piege par l'ethanethiol. Mecanismes
Rheological study of gel phenomena during epoxide network formation in the presence of sepiolite
2012
The dynamic behaviour during the crosslinking of an epoxy polymer near the gel point was monitored using rheological multiple frequency experiments. The influence of a needle-shaped inorganic nanofiller, sepiolite, either non-modified or organically surface modified during the cure process in the presence of an aliphatic and an aromatic hardener was investigated. The validity of various criteria for determining the gel point was examined for the crosslinking of these filled thermosets. The Winter–Chambon criterion at the gel point is obeyed by the unfilled and by the non-modified sepiolite-filled epoxy matrix with either of the two hardeners. However, physical gels are formed in the presenc…
Radioactively labelled epoxides part II. (1) tritium labelled cyclohexene oxide, transstilbene oxide and phenanthrene 9,10-oxide
1980
Tritium labelled cyclohexene oxide, trans-stilbene oxide and phenanthrene 9,10-oxide were prepared with specific activities of 0.7 - 1.1 mCi per mmole starting with monoor diketo compounds. Tritium was introduced by reducing the ketone precursors with tritiated complex metal hydrides. The resulting alcohols were transformed to the epoxides by methods described for the unlabelled compounds. The syntheses require only two or three steps and yield cyclohexene oxide, trans-stilbene oxide and phenanthrene 9,10-oxide, important substrates for the study of epoxide hydratase and glutathione S-transferases in high radiochemical purity.
The Distribution of Carcinogen Metabolizing Enzymes in the Mouse Liver: Comparison of Parenchymal and Non-Parenchymal Cell Populations
1987
The distribution of aminopyrine N-demethylase (APND), ethoxy- resorufin O-deethylase (ERRD), epoxide hydrolase (EH) and glutathione transferase (GST) activities in parenchymal (PC) and non-parenchymal (NPC) cell populations of control and Aroclor 1254-treated C57BL/6N and DBA/2N mice was determined. Furthermore, the metabolism of benzo(a)- pyrene (BP) in PC and NPC of both Aroclor 1254-treated mice strains was examined. Measurable activities of all enzymes investigated were detected in control PC as well as NPC of both mice strains; in all instances the PC possessed greater enzyme activities than did the NPC. The PC and NPC of DBA/ 2N mice had significantly lower ERRD and EH activities than…
Role of Parenchymal Versus Non-Parenchymal Cells on the Control of Biologically Reactive Intermediates
1986
The non-parenchymal cells (NPC) of the liver have the potential to significantly influence the formation of reactive intermediates in the liver because of their critical location along the sinusoids where they are the first cells to encounter blood borne xenobiotics. To study the possible role of the NPC in the metabolism of xenobiotics, populations of NPC and parenchymal cells (PC) were prepared from rats and various xenobiotic metabolizing enzyme activities investigated. The specific activity of every enzyme studied was 12 to 1000% higher in the PC than in the NPC populations and the pattern of activities between the 2 populations was remarkably different. The NPC also displayed a more dr…
Reduction of benzo(a)pyrene mutagenicity by dihydrodiol dehydrogenase
1979
THE enigma of how inert chemicals can exert potent mutagenic, carcinogenic, allergenic and cytotoxic effects has been much debated. It has been learned that such compounds are metabolically converted to chemically reactive species1. In the case of aromatic or olefinic compounds, monooxygenases located in the membranes of the cell can transform these compounds into epoxides2–5 which by virtue of electrophilic reactivity can bind chemically to cellular macromolecules such as DNA, RNA and proteins, thereby disturbing biochemical control mechanisms and leading to the above mentioned toxic effects. The same membranes in which such epoxides are produced possess an enzyme, epoxide hydratase, which…
Enantioselective epoxidation of olefins with molecular oxygen catalyzed by gold(III): A dual pathway for oxygen transfer
2009
Abstract A chiral gold(III) complex has been prepared that performs the epoxidation of olefins in the presence of O 2 , PhIO, or bleach. Catalytic experiments with 18 O show that O 2 is activated on the catalyst and can be directly incorporated into the epoxide through a non-radical mechanism that probably involves formation of gold, oxo, or peroxo species. In addition to this, there is a parallel radical mechanism operating that yields α , β -unsaturated ketones and alcohols as subproducts. Electrochemical and UV–Vis experiments confirmed the occurrence of a Au(III)/Au(I) redox cycle during the catalytic epoxidation in a mechanism sustained by molecular oxygen.
Alkene epoxidations catalysed by Mo(VI) supported on Merrifield's polymer
1999
High conversion and epoxide selectivity from alkenes is achieved with tert-butyl hydroperoxide and a polystyrene-grafted Mo(VI) catalyst, with no noticeable leaching of Mo from the support.
Non-linear effect of 18-crown-6 in propylene oxide polymerization with potassium glycidoxide used as the inimer
2004
A new initiating system containing potassium glycidoxide as the inimer and 18-crown-6 as the activator was used for propylene oxide polymerization. It was found that the rate of the reaction increased together with the crown ether concentration in a rather unexpected way. Two maxima of that parameter were found in the case of crown ether : inimer molar ratio equal to 3:1 and 6:1. On the other hand, the molecular weight of polymers showed two minima in those conditions. The heterogeneity of the reaction mixture and interactions between species present in the system could be responsible for the phenomena observed. The polydispersity of the polymers obtained was equal to about 1.2 and it was i…
Enlarging the Toolbox: Epoxide Termination of Polyferrocenylsilane (PFS) as a Key Step for the Synthesis of Amphiphilic PFS-Polyether Block Copolymer…
2022
Epoxide termination and functionalization of living poly(ferrocenyldimethylsilane) (PFDMS) is introduced by precapping the living PFDMS with a 4/2 molar mixture of 1,1-diphenylethylene and 1,1-dimethylsilacyclobutane acting as a “carbanion pump” system. Subsequent addition of allyl glycidyl ether (AGE) leads to quantitatively functionalized PFDMS–AGE polymers with molecular weights between 1500 and 15 400 g mol–1 and polydispersity indices ≤1.10, carrying one hydroxyl group and an additional allylic double bond. PFDMS–AGE was then applied as a macroinitiator for the living anionic ring-opening polymerization of ethylene oxide (EO) to generate amphiphilic and water-soluble poly(ferrocenyldim…