Supported reducible oxide

G.L. Haller, and D.E. Resasco, Metal-Support Interaction Group VIII Metals and Reducible Oxides, Advances in Catalysis 36, 173-235 (1989). 

Although the gold particle size has importance in systems, which do not contain reducible oxide, such as MgO [201], still the majority of data indicate that high activity is related to the gold/oxide interface. The importance of this experiment is further underlined by the fact that within a 4-10 nm range of Au particle size the system is active [183], but around the gold particle within a short distance the support must be defected in order to activate the reaction components. 

The use of water-soluble reagents and catalysts allows reactions to be performed in aqueous buffered solutions. PEG-supported triarylphos-phine has been used in a Wittig reaction under mildly basic aqueous conditions (Eq. 8.115). The PEG-supported phosphine oxide byproduct can be easily recovered and reduced by alane to regenerate the starting reagent for reuse.312 The aqueous Wittig reaction has also been used in... 

A significant increase of activity can be observed on Rh catalysts supported on reducible oxides. Activity exaltation is severely annihilated when the catalysts are treated in the reaction mixture. Nevertheless, the presence of chlorine largely upset the results. Cl probably slows down the reduction of the support, particularly in the CO+NO mixture. 

H2O2 does not support oxidation is especially significant because the same concentrations of H2O2 support vigorous oxidation of reducing substrates such as aromatic amines and phenylbutazone. Therefore, we conclude that BP and BP-7,8-dihydrodiol are oxidized by a species that is not a functional intermediate of peroxidase catalysis. 

Three randomized clinical trials support the efficacy of bupropion in ADHD. The first used doses up to 6 mg/kg (98) the other two used doses of 100 to 300 mg per day in equally divided daily doses spaced at least 6 hours apart ( 99, 100). The concern with bupropion is its seizure risk, which requires that its daily dose stay below 450 mg per day in adults (i.e., approximately 6.5 mg/kg). Virtually no work has been done to determine the plasma concentrations of bupropion and its three active metabolites in children and adolescents. Hence, it is unknown whether a limit of 6.5 mg per kg is also appropriate for children. No data exist as to whether children are more or less sensitive to bupropion in terms of seizure risk at the same drug concentration. Also, little is known about pharmacokinetic drug-drug interactions that could reduce the clearance of bupropion. For these reasons, cautious dosing is advised when prescribing bupropion for children on other medications that can reduce oxidative drug metabolism (see Chapter 3 and Chapter 7 for more details). 

Analysis of structure-activity relationships shows that various species characterized by different reactivities exist on the surface of vanadium oxide-based catalysts.339 The redox cycle between V5+ and V4+ is generally accepted to play a key role in the reaction mechanism, although opposite relationships between activity and selectivity, and reducibility were established. More recent studies with zirconia-supported vanadium oxide catalysts showed that vanadium is present in the form of isolated vanadyl species or oligomeric vanadates depending on the loading.345,346 The maximum catalytic activity was observed for catalysts with vanadia content of 3-5 mol% for which highly dispersed polyvanadate species are dominant. 

---