Alcohols peroxidation products

Alcohol autoxidation is carried out in the range of 70—160°C and 1000—2000 kPa (10—20 atm). These conditions maintain the product and reactants as Hquids and are near optimum for practical hydrogen peroxide production rates. Several additives including acids, nitriles, stabHizers, and sequestered transition-metal oxides reportedly improve process economics. The product mixture, containing hydrogen peroxide, water, acetone, and residual isopropyl alcohol, is separated in a wiped film evaporator. The organics and water are taken overhead and further refined to recover by-product acetone and the... 

Most ozonolysis reaction products are postulated to form by the reaction of the 1,3-zwitterion with the extmded carbonyl compound in a 1,3-dipolar cycloaddition reaction to produce stable 1,2,4-trioxanes (ozonides) (17) as shown with itself (dimerization) to form cycHc diperoxides (4) or with protic solvents, such as alcohols, carboxyUc acids, etc, to form a-substituted alkyl hydroperoxides. The latter can form other peroxidic products, depending on reactants, reaction conditions, and solvent. 

NADH. Immobilized redox mediators, such as the phenoxazine Meldola Blue or phenothiazine compoimds, have been particularly useful for this purpose (20) (see also Figure 4-12). Such mediation should be useful for many other dehydrogenase-based biosensors. High sensitivity and speed are indicated from the flow-injection response of Figure 3-21. The challenges of NADH detection and the development of dehydrogenase biosensors have been reviewed (21). Alcohol biosensing can also be accomplished in the presence of alcohol oxidase, based on measurements of the liberated peroxide product. 

Oxidative damage to membrane polyunsaturated fatty acids leads to the formation of numerous lipid peroxidation products, some of which can be measured as index of oxidative stress, including hydrocarbons, aldehydes, alcohols, ketones, and short carboxylic acids. 

The ALDs are a subset of the superfamily of medium-chain dehydrogenases/reductases (MDR). They are widely distributed, cytosolic, zinc-containing enzymes that utilize the pyridine nucleotide [NAD(P)+] as the catalytic cofactor to reversibly catalyze the oxidation of alcohols to aldehydes in a variety of substrates. Both endobiotic and xenobiotic alcohols can serve as substrates. Examples include (72) ethanol, retinol, other aliphatic alcohols, lipid peroxidation products, and hydroxysteroids (73). 

First experiments on oxygen atom reactions with hydrocarbons, with the zone of discharge in water vapor, as well as in O2, used as a source of 0 atoms, have shown that the reaction products are formaldehyde, acetaldehyde, acids, alcohols, peroxides, i.e., products of lower degrees of conversion than that yielding H20, CO, and C02. 

Saturated hydrocarbons are homolytically oxidized by complexes (205) into alcohols, ketones and t-butyl peroxide products. The hydroxylation reaction occurs at the more nucleophilic C—H... 

It is known that the first aldehyde metabolite of alcohol, acetaldehyde, stimulates collagen transcription in vitro in hepatic fibroblasts and lipocytes [85,86], suggesting a link with alcoholic liver fibrosis in vivo. Chojkier et al. [84] have shown that the lipid-peroxidation product malondialdehyde also increases collagen production 2-3-fold in cultured foetal fibroblasts. The way in which... 

The second half-reaction of galactose oxidase turnover involves reduction of O2 to form peroxide, H2O2. Although much less is known about this mechanistic step, it is thought that O2 binds to Cu(I). Both substrate-derived protons are transferred to the peroxide product, as determined from the large substrate (alcohol) KIE on O2 reduction evidently hydrogen transfer is fully rate limiting for O2 reduction. Additional work is necessary to develop a more detailed mechanism of O2 reduction. 

Several mechanisms for curing gels are possible however, most have limitations involving either processing or the final gel properties. Condensation type cures form water or alcohol by-products which cause outgassing and voids. Free radical peroxide-activated addition cures make it difficult to control gel consistency from batch to batch. These problems are not evident in the most prevalent cure mechanism used today, the addition of silicon-bonded hydrogen atoms to silicon-bonded olefinic radicals, usually vinyl, in the presence of a few parts per million of a platinum catalyst (I). This system creates no by-products and is easily controlled. 

The product factors which may need consideration include viscocity, cleanliness of fill, whether product froths or is corrosive, coefficient of expansion, volume to vacuity or ullage ratio, etc. Note that alcoholic based products have a higher coefficient of expansion than water, hence need a higher level of vacuity. Vacuity levels normally lie between 2% and 10%. Certain more volatile materials and chemical based products will create internal pressure according to the vapour pressure exerted for a given temperature. In certain instances, e.g. with peroxides, hypochlorites and similar products, pressure may be controlled by the use of venting closure systems. 

High-molecular-weight pectin was extracted from dried citrus peels by hydrolysis with nitric acid at pH =1.6 for 1 hour at 80 °C. Three depolymerized pectin samples were prepared by treating the peels with nitric add at pH = 2.3 for 3 hours at 85 °C in the presence of various amounts of hydrogen peroxide (4-8 ml of 30% H202 per kg of peels). After purifying the slurries by filtration, the slurry syrups were concentrated by ultrafiltration, and the pectin samples were recovered by precipitation into isopropyl alcohol. The products were then dried and ground. 

R. C. Tiruvalam et al. Aberration corrected anal)tical electron microscopy studies of sol-immobilized Au -I- Pd, Au Pd and Pd Au catalysts used for benzyl alcohol oxidation and hydrogen peroxide production, Faraday Discuss., 2011, 152(0), 63-86. 

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