Ruthenium oxidation methods

In the second oxidation method, a metalloporphyrin was used to catalyze the carotenoid oxidation by molecular oxygen. Our focus was on the experimental modeling of the eccentric cleavage of carotenoids. We used ruthenium porphyrins as models of cytochrome P450 enzymes for the oxidation studies on lycopene and P-carotene. Ruthenium tetraphenylporphyrin catalyzed lycopene oxidation by molecular oxygen, producing (Z)-isomers, epoxides, apo-lycopenals, and apo-lycopenones. 

Another useful bimetallic for fuel cell electrodes is Pt/Ru. Ruthenium is readily oxidized to Ru02 by calcination after it is impregnated. The PZC of ruthenium oxide is unknown. Propose a comprehensive sequence of experiments with which the SEA method can be applied for the synthesis of a Pt/Ru bimetallic catalyst supported on carbon. The goal is to have intimate contact between the Pt and Ru phases in the final, reduced catalyst. 

The oxidation of alcohols to the corresponding aldehydes, ketones or acids certainly represents one of the more important functional group transformations in organic synthesis and there are numerous methods reported in the literature (1-3). However, relatively few methods describe the selective oxidation of primary or secondary alcohols to the corresponding aldehydes and ketones and most of them traditionally use a stoichiometric terminal oxidant such as chromium oxide (4), dichromate (5), manganese oxide (6), and osmium or ruthenium oxides as primary oxidants (7). 

A variety of other oxidation conditions were investigated overall, the ruthenium tetraoxide method gave the most consistent results and, importantly, required the least purification. The results obtained are summarized in Table 16. 

These protocols can be regarded as promising because of their simplicity and broad scope. The conventional method for the production of aldehydes from alkenes consists of ozonolysis followed by workup under reducing conditions [72]. The ruthenium-based method, using either oxone or NaI04 as the oxidant, is an interesting alternative. The high selectivity to aldehyde versus carboxylic acid was reached by manipulation of the amount of terminal oxidant (2 Eq.) and the reaction time. 

Other oxidative methods have also been investigated. Thus, oxidation of the nucleosides at C-5 with chromium trioxide-pyridine,346 chromium trioxide-acetic acid,347 or periodate in aqueous acetone containing ruthenium trichloride,348 to give the corresponding uronic acid derivatives, has also been reported. 

If a secondary alcohol is not easily oxidized by other methods the ruthenium(Vin) oxide catalyzed procedure is often recommended. As mentioned previously, this is a strong oxidation method which is not compatible with a number of functional groups. Sodium periodate usually serves as the stoichiometric oxidant, but sodium hypochlorite has also been used in the oxidation of secondary alcohols [94]. Because of the cheap oxidants and a straightforward work-up this reaction is well suited for large-scale oxidations [95]. The TEMPO procedure also employs a cheap stoichiometric oxidant and has been applied in the oxidation of 23 on a kilogram scale [87]. The TPAP-catalyzed method is a milder procedure and many functional groups are stable to these conditions. However, secondary alcohols are still oxidized to ketones in high yield with NMO as the co-oxidant [24]. 

The combined information obtained by the different characterization methods applied allows the conclusion that deposits of ruthenium oxide at BDD, ranging from approximately one hundredth of a monolayer, maintain the physicochemical properties of RUO2, which proves the very limited degree of chemical interaction with the support. The deposits are most probably organized in nanoparticles growing around nucleation sites. When particles and clusters of particles reach a size of 50-60 nm, their charge-storage and catalytic behavior closely resembles that of thick oxide films. 

A review of First Principles simulation of oxide surhices is presented, focussing on the interplay between atomic-scale structure and reactivity. Practical aspects of the First Principles method are outlined choice of functional, role of pseudopotential, size of basis, estimation of bulk and surface energies and inclusion of the chemical potential of an ambient. The suitability of various surface models is discussed in terms of planarity, polarity, lateral reconstruction and vertical thickness. These density functional calculations can aid in the interpretation of STM images, as the simulated images for the rutile (110) surface illustrate. Non-stoichiometric reconstructions of this titanium oxide surface are discussed, as well as those of ruthenium oxide, vanadium oxide, silver oxide and alumina (corundum). This demonstrates the link between structure and reactivity in vacuum versus an oxygen-rich atmosphere. This link is also evident for interaction with water, where a survey of relevant ab initio computational work on the reactivity of oxide surfaces is presented. 

High catalyst activity and utilization of sputtered thin films was demonstrated in operating fuel cells. Optimal sputter-deposition conditions for platinum-ruthenium alloys have been determined. The effect of composition on the performance of Pt-Ru films was studied, and optimal composition has been determined. Novel methods of enhancing surface area and improving porosity have been identified. Co-sputtered ruthenium oxide has been demonstrated not to have any significant beneficial effect on the activity of the catalyst layers. While cost presents a major obstacle to commercialization of DMFCs for mobile applications, this project demonstrates novel means to reduce the catalyst costs in DFMC fuel cells. Efficiency enhancements that are also necessary for DMFCs to be viable will be addressed... 

Both alcohols and aldehydes can be oxidised to carboxylic acids using ruthenium tetroxide an efficient, two-phase (CCl4-aq.NaCl) electro-oxidation method has been developed for the generation of RuO which could be especially useful for oxidations of carbohydrate derivatives, partly protected as acetonides.5 Zinc dichromate... 

Lee Y-H, Oh J-G, Oh H-S, Kim H (2008) Novel method for the preparation of carbon supported nano-sized amraphous ruthenium oxides for super capacitors. Electrochem Commun 10 1035-1037... 

Kim H, Popov BN (2002) Characterization of hydrous ruthenium oxide/carbon nanocomposite supercapacitors prepared by a colloidal method. J Power Sources 104 52-61... 

One oxidative method used an aromatic ring as a carboxyl surrogate. Oxidation of 1.205 with ruthenium oxide, for example, gave 4-aminobutanoic acid (J.2).H9 Similar oxidation of tyramine gave an 86% yield of 3-aminopropanoic acid (i.l). 

There are several other interesting methods that convert alkenes to amino acid derivatives. All include somewhat novel oxidative methods. Ruthenium complex 1.259, for example, was converted to methyl 4-(N,N-dimethylamino)-2-methylbut-anoate (,1.260). In addition, methyl 2-ethyl-4-(N,N-dimethylamino)butanoale... 

The general formula of perovskites is ABO3, and soot combustion perovskite catalysts with many different cations have been reported for both A and B positions [7]. For instance, DoggaU et al. [8] prepared BaRuOs perovskites by coprecipitation method and its catalytic activity was tested for diesel soot oxidation with O2. The catalytic activity was attributed to the dissociative adsorption of oxygen on the catalyst surface, and was postulated that the 120 planes of BaRuOs can have abundant Ru atoms that can facilitate the O2 dissociation. The advantage of using this perovskite with regard to pure ruthenium oxide was attributed to the thermal stability of Ru within the BaRuOs matrix as well as basicity offered by Ba. 

Sharpless oxidation method (RuCls, NaI04 in CHsCN-CC -water) has been shown to oxidise 2, 3 -0-isopropylidene derivatives of ribonucleosides to the uronic acid nucleosides in very high yield under mild, neutral conditions, and potassium persulfate is also effective for recycling the ruthenium reagent in such oxidations the latter procedure was used to make, inter alia, the uronic acid analogue of ACT. Oxidation of isopropylidene uridine with CrOa, PCC or PDC in the presence of acetic anhydride leads to the formation of lactone nucleoside 154 in 50% yield, and several similar cases were reported,... 

Historically, oxidation of diacetone-a-o-glucose (1, l,2 5,6-di-0-isopropylidene-a-D-glucofuranose) was realized by ruthenium tetraoxid and various activated DMSO methods. The latter approach has found industrial application and has been reviewed. Academic laboratories still " rely mainly on chromium (VI) and ruthenium tetraoxide methods. Some of these are rather difficult to scale-up and/or require the use of toxic or expensive reagents. 

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