1-Hydroxyethyl radical

A typical example is seen for 1-hydroxyethyl radical trapped in a y-irra-diated ethanol matrix at 77 K [16]. As is shown in Fig. 2, the cw ESR spectrum of the radical is composed of five lines due to hyperfine interactions with one a proton and three P protons of a methyl group. The hyperfine interaction depends on the location of the P protons with respect to the p. orbital of the unpaired electron. However, the observed hyperfine coupling constant is the same for all the p protons because of the quick rotation of the methyl group in the time scale of the cw ESR measurement. On the other hand, the ESE-detected ESR spectrum is composed of four lines due to the hyperfine interactions with... 

Marfak A, Trouillas P, AUais DP, CaUiste CA, Cook-Moreau J, Duroux J-L. (2004) Reactivity of flavonoids with 1-hydroxyethyl radical A y-radiolysis study Biochim Biophys Acta 1670 28-39. 

The 1-hydroxyethyl radical may be further oxidized, to form aldehydes from primary alcohols, and ketones from secondary alcohols. The only tertiary alcohol to he studied in detail gave the corresponding ketone on irradiation. 

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. " ... 

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 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... 

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]. 

Belkin S, Mehlhorn RJ, Hideg K, Hankovsky O, Packer L (1987) Reduction and destruction rates of nitroxide spin probes. Arch Biochem Biophys 256 232-243 Berdnikov VM, Bazhin NM, Fedorov VK, Polyakov OV (1972) Isomerization of the ethoxyl radical to thea-hydroxyethyl radical in aqueous solution. KinetCatal (English translation) 13 986-987 BerkowitzJ, Ellison GB, Gutman D (1994) Three methods to measure RH bond energies. J Phys Chem 98 2744-2765... 

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). 

In close analogy to the 2-hydroxyethyl radical 21 (R = H) the 2-aminoethyl radical 24 faces a substantial barrier for the (most likely stepwise) 1,2-migration process. A transition state for the concerted migration pathway such as 25 could up to now not be located. What differentiates the amino 1,2-migration from the corresponding hydroxy group migration is that the former appears to be less affected... 

Johnson D.W., Salmon G.A., Pulse Radiolysis of Methanol and Ethanol Acid-Base Behaviour of Hydroxymethyl and Hydroxyethyl Radicals, J. Chem. Soc, Faraday Trans., 1,1975,71,583-591. 

So in conclusion the two sets of adducts (I and V), and (II and III) behave differently and one can conclude that the a-hydroxyethyl radical is a good model for 6-methyldihydrouracil-6-yl radical and a,P-dihydroxyethyl radical is a good model for 6-methyluracil-6-yl and 6-methyl-/-cytosine-6-yl radicals. 

Clot P, Albano E, Eliasson E, Tabone M, Arico S, Israel Y, Moncada C, Ingelman-Sundberg M (1996) Cytochrome P4502E1 hydroxyethyl radical adducts as the major antigen in autoantibody formation among alcoholics. Gastroenterology, 111(1) 206-216. 

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). 

Ethanol metabolism may result in alchohol-induced liver disease, including hepatic steatosis (fatty liver), alcohol-induced hepatitis, and cirrhosis. The principal toxic products of ethanol metabolism include acetaldehyde and free radicals. Acetaldehyde forms adducts with proteins and other compounds. The hydroxyethyl radical produced by MEOS and other radicals produced during... 

The halogenated biphenyls represent a class of compounds where reductive conditions [51] (solvated electron, aromatic radical anions, ketyl radicals) answer the purpose much better than the OH radical. However, this is to be seen in the context that the toxicity of the halogenated biphenyls exceeds that of biphenyl itself by such a wide margin that the latter compound is considered as relatively harmless. Complete removal of the pollutant would still have to rely on the oxidative pathway. A similar situation exists with respect to nitro-aromatics [52] which are also subject to reductive attack, indirectly by the OH radical via a-hydroxyethyl radical generated from the additive ethanol [53]. 

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