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Alkane Oxidation (alkane + oxidation)
Selected AbstractsTowards Photocatalytic Alkane Oxidation: The Insertion of Dioxygen into a Platinum(II),Methyl Bond,ANGEWANDTE CHEMIE, Issue 32 2009Russell Auf der Sonnenseite: Die lichtvermittelte Insertion von Disauerstoff in eine Platin-Methyl-Bindung führt zu einem Methylperoxokomplex (siehe Schema), der sich unter Freisetzung von Formaldehyd zu einem Platin-Hydroxo-Komplex zersetzt. Die Reaktion umfasst die Bildung von Singulett-Sauerstoff und läuft unter 1,atm O2 bei Raumtemperatur in Minuten ab. [source] Alkane oxidation by the system ,tert -butyl hydroperoxide,[Mn2L2O3][PF6]2 (L,=,1,4,7-trimethyl-1,4,7-triazacyclononane),carboxylic acid'JOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 2 2008Yuriy N. Kozlov Abstract The kinetics of cyclohexane (CyH) oxygenation with tert -butyl hydroperoxide (TBHP) in acetonitrile at 50,°C catalysed by a dinuclear manganese(IV) complex 1 containing 1,4,7-trimethyl-1,4,7-triazacyclononane and co-catalysed by oxalic acid have been studied. It has been shown that an active form of the catalyst (mixed-valent dimeric species ,MnIIIMnIV') is generated only in the interaction between complex 1 and TBHP and oxalic acid in the presence of water. The formation of this active form is assumed to be due to the hydrolysis of the MnOMn bonds in starting compound 1 and reduction of one MnIV to MnIII. A species which induces the CyH oxidation is radical tert -BuO. generated by the decomposition of a monoperoxo derivative of the active form. The constants of the equilibrium formation and the decomposition of the intermediate adduct between TBHP and 1 have been measured: K,=,7.4,mol,1,dm3 and k,=,8.4,×,10,2,s,1, respectively, at [H2O],=,1.5,mol,dm,3 and [oxalic acid],=,10,2,mol,dm,3. The constant ratio for reactions of the monomolecular decomposition of tert -butoxy radical (tert -BuO.,, CH3COCH3,+,CH) and its interaction with the CyH (tert -BuO.,+,CyH,,,tert -BuOH,+,Cy.) was calculated: 0.26,mol,dm,3. One of the reasons why oxalic acid accelerates the oxidation is due to the formation of an adduct between oxalic acid and 1 (K,,,103,mol,1,dm3). Copyright © 2007 John Wiley & Sons, Ltd. [source] Gene diversity of CYP153A and AlkB alkane hydroxylases in oil-degrading bacteria isolated from the Atlantic OceanENVIRONMENTAL MICROBIOLOGY, Issue 5 2010Liping Wang Summary Alkane hydroxylases, including the integral-membrane non-haem iron monooxygenase (AlkB) and cytochrome P450 CYP153 family, are key enzymes in bacterial alkane oxidation. Although both genes have been detected in a number of bacteria and environments, knowledge about the diversity of these genes in marine alkane-degrading bacteria is still limited, especially in pelagic areas. In this report, 177 bacterial isolates, comprising 43 genera, were obtained from 18 oil-degrading consortia enriched from surface seawater samples collected from the Atlantic Ocean. Many isolates were confirmed to be the first oil-degraders in their affiliated genera including Brachybacterium, Idiomarina, Leifsonia, Martelella, Kordiimonas, Parvibaculum and Tistrella. Using degenerate PCR primers, alkB and CYP153A P450 genes were surveyed in these bacteria. In total, 82 P450 and 52 alkB gene fragments were obtained from 80 of the isolates. These isolates mainly belonged to Alcanivorax, Bacillus, Erythrobacter, Martelella, Parvibaculum and Salinisphaera, some of which were reported, for the first time, to encode alkane hydroxylases. Phylogenetic analysis showed that both genes were quite diverse and formed several clusters, most of which were generated from various Alcanivorax bacteria. Noticeably, some sequences, such as those from the Salinisphaera genus, were grouped into a distantly related novel cluster. Inspection of the linkage between gene and host revealed that alkB and P450 tend to coexist in Alcanivorax and Salinisphaera, while in all isolates of Parvibaculum, only P450 genes were found, but of multiple homologues. Multiple homologues of alkB mostly cooccurred in Alcanivorax isolates. Conversely, distantly related isolates contained similar or even identical sequences. In summary, various oil-degrading bacteria, which harboured diverse P450 and alkB genes, were found in the surface water of Atlantic Ocean. Our results help to show the diversity of P450 and alkB genes in prokaryotes, and to portray the geographic distribution of oil-degrading bacteria in marine environments. [source] OH concentration time histories in n -alkane oxidationINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 12 2001D. F. Davidson OH radical concentration time histories were measured behind reflected shocks in the oxidation of four n -alkanes: propane, n -butane, n -heptane, and n -decane. Initial reflected shock conditions of these measurements were 1357,1784 K, 2.02,3.80 atm, with fuel concentrations of 300,2000 ppm, and equivalence ratios from 0.8 to 1.2. OH concentrations were measured using narrow-linewidth ring-dye laser absorption of the R1(5) line of the A,X (0,0) transition at 306.5 nm. These concentration time-history measurements were compared to the modeled predictions of eight large n -alkane oxidation mechanisms currently available in the literature and the kinetic implications of these measurements are discussed. These data, in conjunction with recent measurements of n -alkane ignition times and ethylene yields in n -alkane pyrolysis experiments, also performed in this laboratory, provide a unique database of species concentration time histories for n -alkane mechanism validation. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 775,783, 2001 [source] Degradation of isooctane by Mycobacterium austroafricanum IFP 2173: growth and catabolic pathwayJOURNAL OF APPLIED MICROBIOLOGY, Issue 3 2004F. Solano-Serena Abstract Aims:, Isooctane (2,2,4-trimethylpentane), a major component of gasoline formulations, is recalcitrant to biodegradation probably because of the quaternary carbon group it contains. Information on the biodegradability of this hydrocarbon is essential to evaluate its fate in the environment. For these reasons, the degradation kinetics and the catabolic pathway of isooctane were investigated in Mycobacterium austroafricanum IFP 2173, the only strain characterized to use it as sole carbon and energy source. Methods and Results:, The selected strain exhibited a rather moderate maximum growth rate (,max = 0·053 h,1) but degraded isooctane up to 99% with a mineralization yield of 45%, indicating attack of the quaternary carbon group. The GC/MS identification of metabolites, 2,4,4-trimethylpentanoic and dimethylpropanoic (pivalic) acids, which transiently accumulated in the cultures indicated that degradation started from the isopropyl extremity of the molecule and subsequently proceeded by catabolism of the tert -butyl moiety. The degradation of putative metabolic intermediates was investigated. The initial isooctane oxidation system was tentatively characterized. Conclusions:, The isooctane-degrading strain harboured two candidate systems for initial alkane oxidation. Although a cytochrome P450 was induced by isooctane degradation, the functional oxidation system was probably a nonheme alkane monooxygenase as indicated by PCR amplification and RT-PCR expression of an alkB gene. Significance and Impact of the Study:, Isooctane is a recalcitrant branched alkane. A plausible pathway of its degradation by Myco. austroafricanum was put forward. [source] Aqueous catalysis by novel macromolecule metal complexes with molecular recognition abilities,POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 3-4 2001Edward A. Karakhanov Abstract A number of water-soluble macromolecular metal complexes on the basis of polyethers, ,-cyclodextrins, calix[4] and calix[6]arenes functionalized by oligoethylene oxide blocks, catechol, ethylendiamine, acetylacetone, 2,2,-dipiridyl, phosphines and nitrile containing groups have been developed. Complexes showed high catalytic activity in aqueous hydroformylation, biphasic Wacker-type oxidation of various higher olefines, alkane oxidation, hydroxylation of benzene and phenol. These catalysts can be multiply reused. The application of host compounds results the extremely selectivities. Copyright © 2001 John Wiley & Sons, Ltd. [source] Oxidation of alkanes and alcohols with hydrogen peroxide catalyzed by complex Os3(CO)10(µ-H)2,APPLIED ORGANOMETALLIC CHEMISTRY, Issue 6 2010Georgiy B. Shul'pin Abstract Trinuclear carbonyl hydride cluster, Os3(CO)10(µ-H)2, catalyzes oxidation of cyclooctane to cyclooctyl hydroperoxide by hydrogen peroxide in acetonitrile solution. The hydroperoxide partly decomposes in the course of the reaction to afford cyclooctanone and cyclooctanol. Selectivity parameters obtained in oxidations of various linear and branched alkanes as well as kinetic features of the reaction indicated that the alkane oxidation occurs with the participation of hydroxyl radicals. A similar mechanism operates in transformation of benzene into phenol and styrene into benzaldehyde. The system also oxidizes 1-phenylethanol to acetophenone. The kinetic study led to a conclusion that oxidation of alcohols does not involve hydroxyl radicals as main oxidizing species and apparently proceeds with the participation of osmyl species, ,OsO'. Copyright © 2010 John Wiley & Sons, Ltd. [source] | |||||||||||||