Search results for "Oxidation."
showing 10 items of 1877 documents
Kinetics of 4-Methoxybenzyl Alcohol Oxidation in Aqueous Solution in a Fixed Bed Photocatalytic Reactor
2010
WOS: 000280384800004
Photocatalytic oxidation of trans-ferulic acid to vanillin on TiO2 and WO3-loaded TiO2 catalysts
2015
Abstract The photocatalytic oxidation of trans-ferulic acid to vanillin in water has been studied by using various TiO2 and WO3-loaded TiO2 samples as catalysts. Different values of selectivity were obtained depending on the physico-chemical properties of the single samples and a vanillin selectivity of 10% was reached in the presence of the commercial TiO2 Merck. Higher selectivity values were obtained by impregnation of TiO2 with H2WO4 followed by calcination. The increased production of vanillin exhibited by the obtained WO3-loaded TiO2 powders was attributed to a reduced further oxidation of the aldehyde caused by the presence of the practically inactive tungsten trioxide hydrate on the…
Trapping Rare and Elusive Phosphinidene Chalcogenides
2017
Four-membered rings with a P2Ch2 core (Ch=S, Se) and phosphorus in the +3 oxidation state have been synthesized. The utility of these rings as a source of monomeric phosphinidene chalcogenides was probed by the addition of an N-heterocyclic carbene, resulting in a base-stabilized phosphinidene sulfide. Similarly, persistence of the phosphinidene selenide in solution was shown through cycloaddition chemistry with 2,3-dimethylbutadiene at elevated temperatures. The observed reactivity was explained by detailed computational work that established the conditions upon which the P2Ch2 rings can liberate phosphinidene chalcogenides. peerReviewed
Mechanism of the Oxidation of Sulfides by Dioxiranes. 1. Intermediacy of a 10-S-4 Hypervalent Sulfur Adduct
2002
Earlier studies established that dimethyldioxirane (1a) reacts with sulfides 2 in two consecutive concerted electrophilic oxygen-transfer steps to give first sulfoxides 3 and then sulfones 4. The same sequential electrophilic oxidation model was assumed for the reaction of sulfides 2 with the strongly electrophilic methyl(trifluoromethyl)dioxirane (1b). In this paper we report on a systematic and general study on the mechanism of the reaction of simple sulfides 2 with DMDO (1a) and TFDO (1b) which provides clear evidence for the involvement of hypervalent sulfur species in the oxidation process. In the oxidation of sulfides 2a-c, diphenyl sulfide (2d), para-substituted aryl methyl sulfides …
Oxidation of alcohols to carbonyl compounds with CrO3.SiO2 in supercritical carbon dioxide.
2006
Supercritical carbon dioxide (scCO2) is an effective reaction medium to perform the oxidation of primary and secondary aliphatic alcohols to the corresponding carbonyl compounds with chromium trioxide supported on silica. These reactions were performed by flowing a solution of the alcohol in scCO2 through a column containing the supported reagent and recovering the product by depressurization. This method avoids the use of organic solvents and the contamination of the products with chromium species.
Photocatalytic Selective Oxidation of 4-Methoxybenzyl Alcohol to Aldehyde in Aqueous Suspension of Home-Prepared Titanium Dioxide Catalyst
2007
WOS: 000246040000026
Heterogeneous oxidation of pyrimidine and alkyl thioethers in ionic liquids over mesoporous Ti or Ti/Ge catalysts.
2004
Heterogeneous catalytic oxidation of a series of thioethers (2-thiomethylpyrimidine, 2-thiomethyl-4,6-dimethyl-pyrimidine, 2-thiobenzylpyrimidine, 2-thiobenzyl-4,6-dimethylpyrimidine, thioanisole, and n-heptyl methyl sulfide) was performed in ionic liquids by using MCM-41 and UVM-type mesoporous catalysts containing Ti, or Ti and Ge. A range of triflate, tetrafluoroborate, trifluoroacetate, lactate and bis(trifluoromethanesulfonyl)-imide-based ionic liquids were used. The oxidations were carried out by using anhydrous hydrogen peroxide or the urea-hydrogen peroxide adduct and showed that ionic liquids are very effective solvents, achieving greater reactivity and selectivity than reactions p…
Studies on electron-beam irradiation and plastic deformation of medical-grade ultra-high molecular weight polyethylene
2011
Abstract Separated and combined electron-beam irradiation and plastic deformation effects on the structures of ultra-high molecular weight polyethylene (UHMWPE) were studied. It was found that the concentration of carbonyl (ketones, esters and peresters), hydroxyl and vinyl groups increases with the growing dose of adsorbed electrons. It also tends to exhibit a slight increase in the melting point and crystallinity of the samples. A mechanical stress in the polymer was found to accelerate radiation-induced degradation. It was concluded that each of the factors studied (i.e. electron beam sterilization and plastic deformation) had a different impact on the polymer structure. The change in th…
Time–carbonyl groups equivalence in photo-oxidative aging of virgin/recycled polymer blends
2004
AbstractThe photo-oxidation behaviour of polymers is strongly dependent on the initial amount of carbonyl groups along the chains. The growing use of recycled post-consumer polymers coming from products used outdoors and then photo-oxidised, both pure and blended with the same virgin polymer, gives rise to an unpredictable behaviour of weathering resistance of products made with these materials. The present work shows that the carbonyl group–exposure time curves can be shifted along the time axis to give a single generalised master plot. It is then possible to predict the formation of the new carbonyl groups by knowing only the initial amount of the same carbonyl groups. The same shift fact…
Chronic Lymphocytic Leukemia: Correlations Between Oxidative Stress Metabolism and Cytogenetic Subgroups
2008
Abstract The chronic lymphocytic leukemia (B cell-CLL) is a heterogeneous lymphoproliferative disorder susceptible to oxidative stress. The excessive production of reactive oxygen intermediates above the capability of naturally produced antioxidants may result in the instability of essential macromolecules, and represents the molecular basis of many diseases including cancer. Highly reactive radicals interact with DNA inducing a multitude of oxidative modifications, and are implicated in mutagenesis due to misreplication of the damaged base 8-oxo-2′-deoxiguanosine (8-oxo-dG). Furthermore, protooncogene activation and/or tumor suppressor gene inhibition has been reported as a consequence of …