Secondary oxidations

Copper ore minerals maybe classified as primary, secondary, oxidized, and native copper. Primaryrninerals were concentrated in ore bodies by hydrothermal processes secondary minerals formed when copper sulfide deposits exposed at the surface were leached by weathering and groundwater, and the copper reprecipitated near the water table (see Metallurgy, extractive). The important copper minerals are Hsted in Table 1. Of the sulfide ores, bornite, chalcopyrite, and tetrahedrite—teimantite are primary minerals and coveUite, chalcocite, and digenite are more commonly secondary minerals. The oxide minerals, such as chrysocoUa, malachite, and azurite, were formed by oxidation of surface sulfides. Native copper is usually found in the oxidized zone. However, the principal native copper deposits in Michigan are considered primary (5). 

Ethylene oxide secondary oxidation with C-tagged ethylene oxide, to clarify the source of CO2, was done at Union Carbide but not published. This was about 10 years before the publication of Happel (1977). With very limited radioactive supply only a semi-quantitative result could be gained but it helped the kinetic modeling work. It became clear that most CO2 comes from ethylene directly and only about 20% from the secondary oxidation of ethylene oxide. 

As is quite often the case, the hydrolysed form of the oxidant is more reactive than the hexa-aquo species. The stoichiometries suggest dimerisation, rather than secondary oxidation, is the normal fate of the hydrazoyl radical. The variations in ky and k suggest oxidation occurs at the non-protonated nitrogen atom. 

The mechanisms of all three oxidations involve initial slow one-equivalent oxidation to a radical (NH20-, -NHOCH3 and N02-) followed either by rapid secondary oxidation (of NH20- or N02 ) or by radical dimerisation (-NHOCHs). 

Kinetics of the reactions with all the oxidants have been reported (Table 16). The usual product is formic acid, which is the first molecule formed resistant to very rapid secondary oxidation. Six equivalents of Ce(IV) are destroyed in oxidising one molecule of substrate to one of HC02H °, viz. 

Two contrasting conclusions have been reported in the reactions of lithium aluminium hydride in THF with phosphine oxides and phosphine sulphides respectively. The secondary oxide, phenyl-a-phenylethylphos-phine oxide (42), has been found to be racemized very rapidly by lithium aluminium hydride, and this observation casts some doubt on earlier reports of the preparation of optically active secondary oxides by reduction of menthyl phosphinates with this reagent. A similar study of the treatment of (/ )-(+ )-methyl-n-propylphenylphosphine sulphide (43) with lithium aluminium hydride has revealed no racemization. These results have been rationalized on the basis of the preferred site of attack of hydride on the complexed intermediate (44), which, in the case of phosphine oxides (X = O), is at phosphorus, and in the case of the sulphides (X = S), is at sulphur. Such behaviour is comparable to that observed during the reduction of phosphine oxides and sulphides with hexachlorodisilane. ... 

A number of methods are available for following the oxidative behaviour of food samples. The consumption of oxygen and the ESR detection of radicals, either directly or indirectly by spin trapping, can be used to follow the initial steps during oxidation (Andersen and Skibsted, 2002). The formation of primary oxidation products, such as hydroperoxides and conjugated dienes, and secondary oxidation products (carbohydrides, carbonyl compounds and acids) in the case of lipid oxidation, can be quantified by several standard chemical and physical analytical methods (Armstrong, 1998 Horwitz, 2000). 

The origin of many of the components of black tea aroma has been studied. Aldehydes are produced by catechin quinone oxidation of amino acids. Enzymic oxidation of carotenoids during manufacture generates ionones and their secondary oxidation products such as theaspirone and dihydroactinidolide. Oxidation of linoleic acid is responsible for the formation of trans-2-hexenal.82... 

Thus, the primary reactions at the surface of iron are the loss of the metal due to oxidation to the divalent ion and the reduction of O2 gas to either water or hydroxide ion. The formation of rust is actually a secondary oxidation reaction of the Fe2+ ions to Fe3+ with additional O2, forming insoluble Fe2C>3 ... 

Alternative metabolic pathways involve ring-oxidation and peroxidation of arylamines. Although ring-oxidation is generally considered a detoxification reaction, an electrophilic iminoquinone (X) can be formed by a secondary oxidation of the aminophenol metabolite (18,19). Lastly, reactive imines (XI) can be formed from the primary arylamines by peroxidase-catalyzed reactions that involve free radical intermediates (reviewed in 20). 

The major breakthrough in the catalytic asymmetric dihydroxylation reactions of olefins was reported by Jacobsen et al.55 in 1988. Combining 9-acetoxy dihydroquinidine as the chiral auxiliary with /V-methylmorphine TV-oxide as the secondary oxidant in aqueous acetone produced optically active diols in excellent yields, along with efficient catalytic turnover. 

The highest enantioselectivity in the dialkyl-substituted olefines has been obtained with the aryl ethers of DHQD 94a and DHQ 94b. With potassium ferri-cyanide as secondary oxidant, it is possible to carry out the reaction at room temperature, and slow addition of the olefins is not required. Under these conditions, the diols can be obtained in 85-90% yield and excellent enantioselectivity. 

BSEI) showing oxidation of stibnite. (B) SEM/EDS spectra obtained within a secondary oxide (mixture of Fe and Sb oxide). White square is the location of the EDS analysis shown in (B) and SO means secondary oxide. 

Metals are temporarily attenuated as evaporite minerals on the surface or in secondary oxides and hydroxides in the tailings. The evaporites will re-dissolve in wet weather conditions and the secondary minerals become unstable with acidification of the tailings releasing these metals into the environment. 

In this case, the mineralogical studies on the mechanism of sulfide alteration and on the genesis and evolution of secondary oxidation products are of paramount environmental relevance because they allow a better understanding of the source and the mechanisms of release of the ecotoxic elements and the effective... 

The actual isolation of zinc metal on an appreciable scale seems to have occurred first in China in the 10th Century AD (Xu, 1990), using an upwards distillation procedure from secondary (oxidized) zinc minerals. Earlier finds of metallic zinc (such as that at the Agora, noted above) are possibly explained by the chance condensation of small quantities of zinc in the furnace during the production of lead and silver from mixed ores. Much attention has been focused in recent years on northern India, particularly the Zawar region,... 

Changes in mitochondrial stmcture are very relevant during X-ray induced apoptosis. A few hours after irradiation, a hyperpolarisation of A /m is noticed. This likely represents the attempt to restore the depleted ATP levels, stimulating the oxidative burst of surviving mitochondria. If this secondary oxidative stress overcomes the threshold given by mitochondrial thiols, mitochondrial cardiolipin is oxidized and mitochondrial inner membrane allows the leakage of A /m with the consequent initiation of the execution phase. 

Since the reagent is quite expensive, different catalytic procedures have been developed. A very useful procedure involves an amine oxide, such as morpholine-A-oxide, as the stoichiometric secondary oxidant (Scheme 10.4) [29]. 

Entry Ligand OSO4 Secondary oxidant Additive Temp. (°C) Time (hr) %ee... 

A further improvement resulted when potassium hexacyanoferrate(III) was used as secondary oxidant (Table 10.4, entries 5 and 6), in which case the slow addition of olefin was not necessary. O Chemical yields of 85-90% and ee of 89% were obtained by adding at room temperature 0.0025 equiv. of OSO4 to a mixture of 1 equiv. of ( )-3-hexene, 0.25 eq of 4a or 4b, 3 equiv. of K3Fe(CN)6 and 3 equiv. of K2CO3 in rert-butyl alcohol-water (1/1, v/v), followed by reductive working-up with N32S03. 

Refined, bleached, and deodorized oils may contain some nutritionally objectionable compounds - secondary oxidation products, di- and tri-enoic... 

Other functionalized supports that are able to serve in the asymmetric dihydroxylation of alkenes were reported by the groups of Sharpless (catalyst 25) [88], Sal-vadori (catalyst 26) [89-91] and Cmdden (catalyst 27) (Scheme 4.13) [92]. Commonly, the oxidations were carried out using K3Fe(CN)g as secondary oxidant in acetone/water or tert-butyl alcohol/water as solvents. For reasons of comparison, the dihydroxylation of trons-stilbene is depicted in Scheme 4.13. The polymeric catalysts could be reused but had to be regenerated after each experiment by treatment with small amounts of osmium tetroxide. A systematic study on the role of the polymeric support and the influence of the alkoxy or aryloxy group in the C-9 position of the immobilized cinchona alkaloids was conducted by Salvadori and coworkers [89-91]. Co-polymerization of a dihydroquinidine phthalazine derivative with hydroxyethylmethacrylate and ethylene glycol dimethacrylate afforded a functionalized polymer (26) with better swelling properties in polar solvents and hence improved performance in the dihydroxylation process [90]. 

CASRN 13071-79-9 molecular formula C9H21O2PS3 FW 288.43 Soil. Oxidized in soil to its primary and secondary oxidation products, terbufos sulfoxide and terbufos sulfone, respectively (Bowman and Sans, 1982 Chapman et al, 1982 Wei, 1990). Both... 

Parent phthalate Monoester metabolite Secondary oxidized metabolite... 

B[secondary oxidized metaholites and to a variety of conjugates. The most potent carcinogenic metaholite is 7,8-dihydroxy-9,10-epoxy-7,8,9,10-tetrahydrohenzo[ultimate carcinogen hinds predominantly to guanine bases in DNA to form covalent adducts. 

It is worthy of notice that acetaldehyde, a characteristic product of simultaneous oxidation in the fermentation mixture, was detected in these experiments. Its appearance is undoubtedly connected with the process of reduction. Acetaldehyde, which is formed in the absence of air and cannot therefore be a result of secondary oxidation, occurs in approximately constant ratio to the equivalent amount of the methylheptenol. An obvious relationship thus exists between the hydrogenation and the formation of the acetaldehyde. Presumably a disturbance of the normally correlated processes takes place, in the sense of the theory of fermentation. Whereas acetaldehyde normally is reduced to ethyl alcohol, in this case the intermediary acetaldehyde and the added ketone compete for the hydrogen. It thus follows that at least in the initial stage the amount of acetaldehyde which is not reduced must equal the amount that is displaced as a result of interference by the ketone. 

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