Ethyl hydroperoxide, decomposition

Ethylhexyl nitrate, 2 23 2-Ethylhexylpotassium, 14 256 2-Ethylhexyl salicylate, 22 16 2-Ethylhexylsodium, 14 255 Ethyl hydroperoxides, decomposition hazards of, 18 490 Ethylhydroxyethylcellulose (EHEC),... 

Ethyl disulfide, IV, 95 Ethyl hydroperoxide, decomposition by catalase, V, 53... 

Concerning the mode of formation of ES, we prefer the concept that the substrate in a monolayer is chemisorbed to the active center of the enzyme protein, just as the experimental evidence pertaining to surface catalysis by inorganic catalysts indicates that in these reactions chemisorbed, not physically adsorbed, reactants are involved. Such a concept is supported by the demonstration of spectroscopically defined unstable intermediate compounds between enzyme and substrate in the decomposition by catalase of ethyl hydroperoxide,11 and in the interaction between peroxidase and hydrogen peroxide.18 Recently Chance18 determined by direct photoelectric measurements the dissociation con-... 

Solvent Effect. The effect of solvent when using an organic soluble molybdenum catalyst is shown in Table IV. Nonpolar solvents such as benzene and methylcyclohexane give higher conversions and yields than polar solvents such as ethyl alcohol and tert-butyl alcohol. Acetone is an especially poor solvent. The low conversion is caused by competition between the solvent and hydroperoxide for molybdenum catalyst. The poor yield of epoxide is primarily caused by hydroperoxide decomposition... 

Hydroperoxide Levels. In thermally oxidized fats hydroperoxides are usually very low. At higher temperatures, oxidation proceeds rapidly and the rate of hydroperoxide decomposition exceeds that of hydroperoxide formation (17,18). For example, when ethyl linoleate was oxidized at 70°C, peroxide content reached a maximum of 1777 meq/kg after 6 hr then decreased to 283 meq/kg after 70 hr. At 250°C, on the other hand, peroxide value reached a maximum of only 198 meq/kg after 10 min, and was zero after 30 min. 

The products of lipid oxidation in monolayers were also studied. Wu and coworkers (41) concluded that epoxides rather than hydroperoxides might be the major intermediates in the oxidation of unsaturated fatty acids adsorbed on silica, presumably because of the proximity of the substrate chains on the silica surface. In our work with ethyl oleate, linoleate and linolenate which were thermally oxidized on silica, the major decomposition products found were those typical of hydroperoxide decomposition (39). However, the decomposition patterns in monolayers were simpler and quantitatively different from those of bulk samples. For example, bulk samples produced significantly more ethyl octanoate than those of silica, whereas silica samples produced more ethyl 9-oxononanoate than those of bulk. This trend was consistent regardless of temperature, heating period or degree of oxidation. The fact that the same pattern of volatiles was found at both 60°C and 180°C implies that the same mode of decomposition occurs over this temperature range. 

Gas phase kinetic results (Table 64) on hydroperoxide decompositions (methyl, ethyl, isopropyl and t-butyl hydroperoxide) are very poor. Since the thermochemistry is fairly well established for these reactions, and since observed activation energies are as much as 6 kcal.mole lower than the reaction enthalpies, it is apparent that the reported parameters cannot be those for the unimolecular hydro-peroxy bond fission processes. Surface catalysis was considerable in all experimental systems. It therefore seems likely that the true homogeneous reactions were never completely isolated. 

In contrast to silver-catalysed cumene oxidation, the evidence concerning the mechanism of copper-catalysed reactions favours radical initiation via surface hydroperoxide decomposition. Gorokhovatsky has shown that the rate of ethyl benzene oxidation responds to changes in the amount of copper(ii) oxide catalyst used, in a manner which is characteristic of this mechanism. Allara and Roberts have studied the oxidation of hexadecane over copper catalysts treated in various ways to produce different surface oxide species, Depending on the catalyst surface area and surface oxide species present, a certain critical hydroperoxide concentration was necessary in order to produce a catalytic reaction. At lower hydroperoxide levels, the reaction was inhibited by the oxidized copper surface. XPS surface analysis of the copper catalysts showed a... 

The products of autoxidation and photo-oxidation of ethers are the same [187,287,288]. Aldehydes, alcohols, acids, and esters are the main products of hydroperoxide decomposition [186,187,202,283—285,289,290]. For example, ethanol, acetaldehyde, acetic acid, ethyl acetate, and ethyl formate were found in the products of diethyl ether oxidation [186,188, 202,203]. Their formation may be explained by the scheme... 

Alkoxyall l Hydroperoxides. These compounds (1, X = OR , R = H) have been prepared by the ozonization of certain unsaturated compounds in alcohol solvents (10,125,126). 2-Methoxy-2-hydroperoxypropane [10027-74 ] (1, X = OR , R" = methyl), has been generated in methanol solution and spectral data obtained (127). A rapid exothermic decomposition upon concentration of this peroxide in a methylene chloride—methanol solution at 0°C has been reported (128). 2-Bromo-l-methoxy-l-methylethylhydroperoxide [98821-14-8]has been distilled (bp 60°C (bath temp.), 0.013 kPa) (129). Two cycHc alkoxyaLkyl hydroperoxides from cyclodecanone have been reported (1, where X = OR R, R = 5-oxo-l, 9-nonanediyl) with mp 94—95°C (R" = methyl) and mp 66—68°C (R" = ethyl) (130). Like other hydroperoxides, alkoxyaLkyl hydroperoxides can be acylated or alkylated (130,131). 

The only accident that involves a saturated ester is the result of an attempt to extract an organic residue containing hydrogen peroxide with ethyl acetate. The latter was mixed with methanol and refluxed with the residue and hydrogen peroxide in an aqueous solution. A second extraction was carried out with acetate and the liquid was then evaporated. The small quantity of the compound that remained after the evaporation detonated violently. It was thought that this detonation was the result of the violent decomposition of methyl hydroperoxide, peracetic acid and/or ethyl peracetate. 

When C4H80 is diluted by water to 80 volume %, the only product of C4H80 oxidation is acetic acid (99% per methyl ethyl ketone reacted) formed by ketone hydroperoxide conversion. The reason for this increase in the reaction selectivity is that the rate of decomposition of the radical complex R02. . . HOH is lower than that of free R02, while the decrease in the rate of reaction of R02. . . HOH with methyl ethyl ketone is somewhat offset by the higher dielectric constant of the medium. 

The slow combustion reactions of acetone, methyl ethyl ketone, and diethyl ketone possess most of the features of hydrocarbon oxidation, but their mechanisms are simpler since the confusing effects of olefin formation are unimportant. Specifically, the low temperature combustion of acetone is simpler than that of propane, and the intermediate responsible for degenerate chain branching is methyl hydroperoxide. The Arrhenius parameters for its unimolecular decomposition can be derived by the theory previously developed by Knox. Analytical studies of the slow combustion of methyl ethyl ketone and diethyl ketone show many similarities to that of acetone. The reactions of methyl radicals with oxygen are considered in relation to their thermochemistry. Competition between them provides a simple explanation of the negative temperature coefficient and of cool flames. 

Little can be said about the pre-exponential factor. It is lower than that reported by Kirk and Knox (20) for the decomposition of ethyl and terf-butyl hydroperoxide, but it is still in the expected range for a uni-molecular fragmentation into two radicals (9). 

Ti-MOR promoted the ring hydroxylation of toluene, ethylbenzene and xylenes with negligible oxidation of the ethyl side chain [59]. In the same study, however, and in contrast to earlier ones, a similar result was also reported for TS-1. No oxidation of benzylic methyls was observed. Cumene yielded mainly the decomposition products of cumyl hydroperoxide. The oxidation of t-butylbenzene was negligibly low. The reachvity order, toluene > benzene > ethylbenzene > cumene, reflects the reduced steric constraints in the large pores of mordenite. Accordingly, the rate of hydroxylation ofxylene isomers increased in the order para < ortho < meta, in contrast to the sterically controlled one, ortho < meta para, shown on TS-1. It is worth menhoning that the least hindered p-xylene exhibited the same reactivity on either catalyst. 

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