Hydroxyethyl radicals, reaction

In a study directed to the analysis of the role of Fe and the generation of H2O2 in Escherichia coli (McCormick et al. 1998), hydroxyl radicals were specihcally trapped by reaction with ethanol to give the a-hydroxyethyl radical. This formed a stable adduct with a-(4-pyridyl-l-oxide)-iV-t-butyl nitroxide that was not formed either by superoxide or hydroxyl radicals. The role of redox-reactive iron is to use EPR to analyze the EPR-detectable ascorbyl radicals. 

Selected entries from Methods in Enzymology [vol, page(s)] Activity in ethanol oxidation, 233, 118 in hydroxyethyl radical formation analysis with reconstituted vesicles, 233, 127 characterization, 233, 123-125 monooxygenase activity, 231, 574-575 reductase [hemoglobin-catalyzed reactions with, 231, 573-574 oxygen concentration and, 231, 579 pH dependence, 231, 580 reaction mixtures, 231, 578 oxygen content, measurement, 231, 587-588 reductase concentration and, 231, 580 time dependence, 231, 578 preparation, 231, 577]. 

The addition of carbon-centered radicals to C-C double bonds (for a review see Giese 1983) is the key reaction in the free-radical-induced polymerization. In general, the rate constants of these reactions are only moderately high, but this process becomes fast and efficient, because in technical applications the polymerizing olefin is usually present at high concentrations. In aqueous solutions, the rate constant of the addition of the hydroxyethyl radical to ethene [reaction (29)], a non-activated C-C double bond, has been determined at 3 x 104 dm3 mol1 s1 (Soylemez and von Sonntag 1980). 

Berdnikov VM, Bazhin NM, Fedorov VK, Polyakov OV (1972) Isomerization of the ethoxyl radical to the a-hydroxyethyl radical in aqueous solution. Kinet Catal (EngITransI) 13 986-987 Bonifacic M, Asmus K-D (1984) Adduct formation and absolute rate constants in the displacement reaction of thiyl radicals with disulfides. J Phys Chem 88 6286-6290 Bonifacic M, Mockel H, Bahnemann D, Asmus K-D (1975a) Formation of positive ions and other primary species in the oxidation of sulphides by hydroxyl radicals. J Chem Soc Perkin Trans 2 675-685... 

The allyl radical can react with another -CH2OH to form either the hydroxyethyl derivative [reaction (199)] or its isomer with an exocyclic double bond [reactions (200)]. 

The other type of reaction proposed involves attack by iron (III) cations on the substrate, or its oxidation product(s), with peroxide functioning as a rapid re-oxidizer. Thus, ferric ion oxidizes glycosuloses to keto acids, dihydroxymaleic acid to mesoxalaldehydic acid, and the 1-hydroxyethyl radical to acetaldehyde. " ... 

It was originally thought that some OH radicals must abstract hydrogen atoms from ethylene to form C2H3 radicals (14), but it is now concluded that all OH radicals add to ethylene (Reaction 1) and that the -hydroxy-ethyl radicals enter into reactions, not all of which give rise to acetaldehyde (13). Other recent evidence also supports this view (4). The absorption spectrum of the -hydroxyethyl radicals is similar to that of the a-hydroxyethyl radicals which can be prepared from ethyl alcohol (13). 

The rate constants for the free-radical-induced haemolysis of human erythrocytes have been calculated from haemolysis curves and compared with those obtained from experiments with erythrocyte ghosts treated with various radical initiators. The authors concluded that their reaction model (lipid peroxidation/protein oxidation) may be useful in analysing radical-induced haemolysis. In recent years there has been considerable interest in the role the 1-hydroxyethyl radical in the toxic effects of ethanol. Recent studies have shown that the 1-hydroxyethyl radical inactivates the antioxidant enzymes glutathione reductase, glutathione oxidase, and superoxide dismutase. These results indicate that a prolonged generation of the 1-hydroxyethyl radical in animal cells may lower the antioxidant defence status, thus contributing to oxidative stress and toxicity. ... 

The value of Gibbs free energy of the nonsubstituted dioxolenium ion 24 cyclization equals -11.1 kJ/mol and shows that this reaction is a spontaneous process (Fig. 8.2). The substituent at the 1st carbon atom in the hydroxyethyl radical on the dioxolenium ion raises the thermodynamic advantage of the hydrogenated furans formation in the case of the methyl substituent the AG° is -15.3kJ/mol, the ethyl group (26) reduces the value of the Gibbs free energy to -21.4 kJ/mol. 

The photodecarboxylation of chromone-2-carboxylic acid in aerated and deaerated ethanol solution was studied by TR EPR and the chemiluminescence technique. The two reaction products 4-hydroxy-coumarin and 2-(F-hydroxyethyl)chromone are generated through the addition of ground-state oxygen molecules to the excited flavone, and through recombination between ketyl radicals and 1-hydroxyethyl radicals followed by the release of CO2, respectively. An anomalous CIDEP behaviour of the ketyl radical was observed by the addition of hydrochloric acid in the photoreduction of chromone-2-car-boxylic acid. The effects observed are explained by the simultaneous reactions... 

These results are consistent with a free-radical reaction mechanism. A puzzling aspect of the reaction, however, is the exclusion of add6d reactive vinyl monomers such as acrylamide or hydroxyethyl methacrylate from the copolymer product. Clearly the reaction is not a normal radical process. Roitman and Harwood dispute the earlier suggestion of an alternating structure for copolymers produced by spontaneous polymerization based on CNMR spectral analysis. Salamone and coworkers [63] have interpreted data from UV-Vis... 

Hydroxyacetaldehyde is also formed as a minor product in the OH-initiated oxidation of ethene via reaction of the l-oxy-2-hydroxyethyl radical with O2. For higher alkenes, the equivalent radicals rapidly dissociate to form two aldehydes e.g., for propene the products are CH3CHO and CH2O, and the radicals do not generate hydroxyaldehydes. 

Edelbiittel-Einhaus, J., K. Hoyermann, G Rohde, and J. Seeba (1992), The detection of the hydroxyethyl radical by REMPI/mass-spectrometry and the appheation to the study of the reactions CH3CHOH - - O and CH3CHOH -I- H, 24th Symposium on Combustion, The Combustion Institute, pp.661—668. 

Grotheer, H.-H., G. Riekert, D. Walter, and Th. Just (1988), Reactions of hydroxymethyl and hydroxyethyl radicals with molccnlar and atomic oxygen, 22nd Symposium (International) on Combustion (Combnstion Institnte, Pittsburgh, PA, 1989), pp.963-972. 

Even though the radical attacking ethyl alcohol in the above reaction generated a-hydroxyethyl rather then ethoxy free radical, there seems to be little or no tendency for alkoxy free radicals to rearrange to a-hydroxyalkyl radicals. Thus in the reaction... 

Poly methacrylates and copolymers of butadiene and methacrylate having /arious pyrimidine derivatives (Figures 1, and 2) were prepared by free radical polymerization of the methacrylate monomers (14-16). In the case of the poly(MAOT -alt-MAOT3Me )> the polymer was obtained by the reaction of the polymethacrylic anhydride with the hydroxyethyl... 

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