Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Hydroperoxide distribution

Table 1 Hydroperoxide distribution in dry gas-phase ozonolysis as % of alkene a dash means "not detected". Table 1 Hydroperoxide distribution in dry gas-phase ozonolysis as % of alkene a dash means "not detected".
For chromatographic sorbents it is necessary that the polymeric cover be uniformly distributed over the silica surface and chemically coupled to it. The appropriate introduction of the initiator is one of the decisive steps of this task. The first method (binding to the surface) increases the yield of grafted polymer. However in this case a large amount of homopolymer is formed. This disadvantage could be prevented by the application of hydroperoxide initiators in combination with the proper redox-agents [78-81],... [Pg.161]

Interestingly, one-electron oxidants partly mimic the effects of OH radicals in their oxidizing reactions with the thymine moiety of nucleosides and DNA. In fact, the main reaction of OH radicals with 1 is addition at C-5 that yields reducing radicals in about 60% yield [34, 38]. The yield of OH radical addition at C-6 is 35% for thymidine (1) whereas the yield of hydrogen abstraction on the methyl group that leads to the formation of 5-methyl-(2 -de-oxyuridylyl) radical (9) is a minor process (5%). Thus, the two major differences in terms of product analysis between the oxidation of dThd by one-electron oxidants and that by the OH radical are the distribution of thymidine 5-hydroxy-6-hydroperoxide diastereomers and the overall percentage of methyl oxidation products. [Pg.16]

The quality of the polymer, its photo-oxidation and thermo-oxidation history expressed in concentration of hydroperoxides, carbonyl groups or of other oxidized structures and terminal groups. The rate of an oxidative attack may then be related to the average molar mass and to its distribution, and to the ratio of amorphous/crystalline structures. Polymers cannot be simply ordered according to the intensity of light emission at a given temperature. The chemiluminescence-time patterns are related with the rate of sample oxidation, but they may differ from one to the next polymer. [Pg.468]

Ardelt BK, Borowitz JL, Maduh EU, et al. 1994. Cyanide-induced lipid peroxidation in different organs subcellular distribution and hydroperoxide generation in neuronal cells. Toxicology 89(2)... [Pg.238]

Godeas, C., Sandri, G., and Panfili, E., 1994, Distribution of phospholipid hydroperoxide glutathione peroxidase (PHGPx) in rat testis mitochondria. Biochim. Biophys. Acta, 1191 147-150... [Pg.35]

Oxidation of sulfides and sulfoxides using Oxone dispersed on silica gel or alumina was reported . A study of surface mediated reactivity of Oxone compared its reactivity with that of ferf-butyl hydroperoxide. Oxidation of sulfides to sulfones in aprotic solvents mediated by Oxone on wet montmorillonite or clay minerals proceeds in high yields. Interestingly, when Oxone on alumina is applied for selective oxidation of sulfides in aprotic solvents, the product distribution is temperature-dependent and sulfoxides or sulfones are obtained in good to excellent yields (equation 56) . ... [Pg.1025]

As the quasi-axial hydrogens are in more favorable positions than are the corresponding quasi-equatorial (e ) hydrogens at C3 and C6, the formation of hydroperoxides corresponding to the alcohols 22,26 and 18,21 should be favored over those corresponding to 23,27 and 17,20, respectively. This is the case, as the product distribution... [Pg.47]

A3-Carene 168) delivers only three frans-alcohols (169-171) after reduction of the primarily formed hydroperoxides.199-200 The observed product distribution, which practically is 169 170 171 — 2 1 1, is explained by assuming that only the boat conformation 168a takes part in the hydroperoxidation reaction.200 This being the case, the ratio of 169 (170 + 171) should be 1 1, and the ratio of 170 171 should also be 1 1, since attack of oxygen at C3 and C4 should follow a statistical... [Pg.63]

Dimethylcyclohexene (209) is converted to two tertiary hydroperoxides, 210 (12%) and 211 (88%).85,135 1-Methylcyclohexene (30) gives rise to 45% of the tertiary hydroperoxide 31 and to 55% of a non-resolved mixture of secondary hydroperoxides, 52.135 Since the ratio tertiary/secondary hydroperoxides is the same as with limonene (16) and carvomenthene (19), a similar product distribution among the secondary hydroperoxides 32 as was found for 16 and 19 has been assumed. No product distribution has been reported for the photosensitized oxygenation of 1-methylcyclopentene, 213.85,123... [Pg.78]

However, organic peroxides will still form in stored fuel, and their gradual accumulation can contribute to elastomer degradation throughout the fuel storage and distribution system. Hydroperoxide formation and accumulation can be readily controlled by the addition of low levels of traditional fuel oil stabilizers. [Pg.56]

Tremmel, H. G., W. Junkermann, and F. Slemr, Distribution of Organic Hydroperoxides during Aircraft Measurements over the Northeastern United States, J. Geophys. Res., 99, 5295-5307 (1994). [Pg.654]

The haem peroxidases are a superfamily of enzymes which oxidise a broad range of structurally diverse substrates by using hydroperoxides as oxidants. For example, chloroperoxidase catalyses the regioselective and stereoselective haloge-nation of glycals, the enantioselective epoxidation of distributed alkenes and the stereoselective sulfoxidation of prochiral thioethers by racemic arylethyl hydroperoxides [62]. The latter reaction ends in (i )-sulfoxides, (S)-hydroperoxides and the corresponding (R)-alcohol, all In optically active forms. [Pg.497]

Metal ions [Co(III), Mn(m), Cu(II)] have a pronounced effect on the rate and product distribution of autoxidation. In the presence of metal ions, secondary transformations become dominant and selectivity in the formation of benzylic hydroperoxide 100 decreases. [Pg.500]


See other pages where Hydroperoxide distribution is mentioned: [Pg.492]    [Pg.252]    [Pg.53]    [Pg.492]    [Pg.252]    [Pg.53]    [Pg.204]    [Pg.42]    [Pg.438]    [Pg.168]    [Pg.599]    [Pg.58]    [Pg.464]    [Pg.121]    [Pg.54]    [Pg.186]    [Pg.317]    [Pg.348]    [Pg.472]    [Pg.604]    [Pg.623]    [Pg.885]    [Pg.929]    [Pg.57]    [Pg.61]    [Pg.67]    [Pg.31]    [Pg.348]    [Pg.472]    [Pg.604]    [Pg.623]    [Pg.885]    [Pg.929]    [Pg.480]    [Pg.21]    [Pg.359]   


SEARCH



Alkyl hydroperoxides product distribution

© 2024 chempedia.info