Hydroperoxides yield

Acidic hydrolysis of these hydroxyaLkyl hydroperoxides yields carboxyUc acids, whereas basic hydrolysis regenerates the parent aldehyde, hydrogen peroxide, and often other products. When derived from either aldehydes or cycHc ketones, peroxides (1, X = OH, = H, R, = alkylene or... 

As mentioned in the introduction, there are conflicting views as to the contributions made to polymer degradation by various initiating species. Among these species, in addition to ketones, hydroperoxides are some of the more important chromophores. As it is known, the photolysis of hydroperoxides yields alkoxy and hydroxy radicals. In polymers, in the presence of oxygen, these radicals lead to the secondary formation of peroxy radicals. The latter in turn are converted by hydrogen abstraction into new hydroperoxides (Scheme I) ... 

Table 5.1 Catalytic asymmetric epoxidation of allylic alcohols using a combination of titanium wopropoxide. enantiomerically pure tartrate ester ((+)-DET or (+)-DIPT) and rerr-butyl hydroperoxide (yield and enantiomeric excess, according to the relevant publication). ...

Oxygen-oxygen bond in peroxides and hydroperoxides is cleaved very easily by catalytic hydrogenation over platinum oxide [661,662], over palladium [75, 662, 663, 664] or over Raney nickel [66S. Hydroperoxides yield alcohols... 

TABLE 19. Comparison of published results for the asymmetric epoxidation of aUyhc alcohols employing chiral hydroperoxides, (yields are given ee and abs. configuration of the epoxides obtained are given in parentheses)... 

TABLE 29. Results of the titanium-catalyzed asymmetric sulfoxidation with optically pure hydroperoxides (yields are given and ee values are given in brackets)... 

The peroxidase-catalyzed oxidation of ABTS (103) by H2O2 can also be performed by hydroperoxides, yielding a green-colored free radical. This reaction, catalyzed by HRP-C, was applied to the identification of an oxidation product of skatole isolated by HPLC, as a hydroperoxide (40). This assignment was confirmed by MS analysis (Section V.C.3) . 

We have defined also, another parameter F, which corresponds to a theoretical hydroperoxide yield. F is the ratio of the number of non-coupled macromolecule (N ) to the total number of macromolecules after reaction ... 

Results of product studies of three experiments in Table II are given in Table III. Hydroperoxide yields based on AOo vary from 7 to 92%, and the yields increase with increasing isobutane pressure, although there is some scatter that may be caused by wall decomposition. From the yields of methanol and tert-butyl alcohol after reduction, nearly all of the hydroperoxide formed at high isobutane pressures is tert-butyl hydroperoxide. The yields of hydroperoxide at high isobutane pressures are comparable to those found in the liquid phase at 50° and 100°C. (Table I) and those reported by Winkler and Heame for liquid-phase runs at 125°C. (34). 

Above 250°C. we approach, in the gas phase, what is known as the cool flame regime. This is characterized by induction periods and by the appearance of pressure peaks and luminescent phenomena in the oxygen-hydrocarbon system. The consensus of present data seems to support the contention that these cool flames arise from the secondary decomposition of the hydroperoxides produced by the low temperature chain. The unimolecular decomposition of the hydroperoxide yields active alkoxy and hydroxyl radicals ... 

For example polymethyl acrylate was treated with phosphorus penta-chloride to form copolymers containing 26.6 and 37.8% acid chloride units these copolymers, by treatment with tert-butyl hydroperoxide, yield 4.9 to 6% perester containing polymers which were used for grafting styrene, vinyl acetate, acrylonitrile (177). 

The same holds for t-BuOOH and Fe phthalocyanines encapsulated in zeolites or adsorbed on carbon black (121, 124). On the other hand, hydroperoxides have been detected as products in the oxidation of ds-pinane by t-BuOOH in the presence of zeolite Y-encapsulated FePc (133). This is irrefutable evidence of trapping of a radical by dissolved O2. Superior hydroperoxide yields are obtained with FePc in zeolite NaY in comparison with the homogeneous reaction, particularly at subambient temperature ... 

The experimental results showed that, during the first 20 h of irradiation, the photochemical behavior of the blend may be related to that of PVME. To understand better the results of the surface analysis and to try to explain the phase separation phenomenon, a correlation should be made with PVME results. The IR analysis of the photooxidation of PVME homopolymer showed that during the first 5-6 h of irradiation an important increase in a band at 3290 cm-1 was observed [4]. This band has been attributed to tertiary hydroperoxides. For prolonged irradiations, the hydroperoxide absorption band decreased. The decomposition of hydroperoxides yields acetates ... 

Epoxidation of enones 37 with alkaline tert-butyl hydroperoxide yielded epoxides 38 as single diastereomers in excellent yields. Epoxy ketones were further transformed into racemic quadrone90. 

As oxidation normally proceeds very slowly at the initial stage, the time to reach a sudden increase in oxidation rate is referred to as the induction period (6). Lipid hydroperoxides have been identified as primary products of autoxidation decomposition of hydroperoxides yields aldehydes, ketones, alcohols, hydrocarbons, volatile organic acids, and epoxy compounds, known as secondary oxidation products. These compounds, together with free radicals, constitute the bases for measurement of oxidative deterioration of food lipids. This chapter aims to explore current methods for measuring lipid oxidation in food lipids. 

Previously, we have examined the formation of amino acid hydroperoxides following exposure to different radical species [100]. We observed that valine was most easily oxidised, but leucine and lysine are also prone to this modification in free solution. Scheme 12 illustrates the mechanism for formation of valine hydroperoxide. However, tertiary structure becomes an important predictor in proteins, where the hydrophobic residues are protected from bulk aqueous radicals, and lysine hydroperoxides are most readily oxidised. Hydroperoxide yield is poor from Fenton-derived oxidants as they are rapidly broken down in the presence of metal ions [101]. Like methionine sulphoxide, hydroperoxides are also subject to repair, in this case via glutathione peroxidase. They can also be effectively reduced to hydroxides, a reaction supported by the addition of hydroxyl radical in the presence of oxygen. Extensive characterisation of the three isomeric forms of valine and leucine hydroxides has been undertaken by Fu et al. [102,103], and therefore will not be discussed further here. 

Catalytic oxidation of cyclohexane using [Co(r 2-N03)(K3-jpCF3,CH3 N Me and cumene hydroperoxide yields a mixture of cyclohexanol and cyclohexanone.57... 

Photochemical reactions of materials enclosed in zeolites can lead to different proportions of products, or in some cases, to different products than those run in solutions.207 The distribution can vary with the zeolite. The enhanced selectivity in the oxidation of hydrocarbons with oxygen208 was mentioned in Chap. 4. The oxidation of cyclohexane in NaY zeolite with oxygen and visible light to yield cyclohexane hydroperoxide with complete selectivity at more than 40% conversion may have considerable industrial potential. Heating the hydroperoxide yields only cyclohexanone which can be oxidized to adipic acid for use in making nylon 6,6.209... 

Treatment of the tetraisopropyl ester (98 R = OPr ) with t-butyl hydroperoxide yields the t-butyl ester (99), a result which is in contrast with the formation of diisopropylphosphinic acid from the same reaction with the tetrasulphide (97 R = Pr ). ... 

Hemiperoxyacetals derived from allylic hydroperoxides yield 6-substituted... 

Ozonolysis in water was carried out by mixing a solution of the alkene in water (water/acetonitrile in the case of isoprene and the pinenes) with an aqueous solution of ozone The hydroperoxide yields are in Table 3. The only significant products were 1-HAHPs [4]. 

The function of an antioxidant is often to divert the peroxy radicals and thus prevent a chain process. Other antioxidants function by reacting with potential initiators, and thus retard oxidative degradation by preventing initiation of chains. Many sulfiu and phosphorus compounds are believed to function in the latter way. In particular, hydroperoxides that are potential chain initiators are also products of autoxidation. This fact gives autoxidations the potential of being autocatalytic, since the more oxidation products formed, the higher the initiator concentration. Divalent sulfur compounds and trivalent phosphorus compounds can reduce hydroperoxides, yielding stable products ... 

Catalytic action by the pivaloylmethane chelate of Co(II), [Co(dpm)2] appears to occur via a two step initiation sequence in which the 2+ state of the metal reacts with hydroperoxide yielding r-BuO , equation (139), after which the 3+ state reacts with a second hydroperoxide, yielding r-BuOO", equation (140). 

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