Radical acid, oxidizing

Nonaqueous Bases Nonaqueous Nucleophiles Organometallic Catalytic Reduction Acidic Reduction Basic or Neutral Reduction Hydride Reduction Lewis Acids Soft Acids Radical Addition Oxidizing Agents... 

Functional groups that stabilize radicals would be expected to increase susceptibility to autoxidation. This is illustrated by two cases that have been relatively well studied. Aldehydes, in which abstraction of the aldehyde hydrogen is fecile, are easily autoxidized. The autoxidation initially forms a peroxycarboxylic acid, but usually the corresponding carboxylic acid is isolated because the peroxy acid oxidizes additional aldehyde in a... 

These include the mitochondrial respiratory chain, key enzymes in fatty acid and amino acid oxidation, and the citric acid cycle. Reoxidation of the reduced flavin in oxygenases and mixed-function oxidases proceeds by way of formation of the flavin radical and flavin hydroperoxide, with the intermediate generation of superoxide and perhydroxyl radicals and hydrogen peroxide. Because of this, flavin oxidases make a significant contribution to the total oxidant stress of the body. 

The relative rates of oxidation of phenylmethanes cover too small a range to be compatible with carbonium ion formation cf. the discussion on chromic acid oxidation of diphenylmethane, p. 295), and an initial reaction to give a radical plus Cr(V) followed by rapid transfer of a second electron to form Cr(IV) is more... 

Recently Mosher and Driscoll 2 have noted that the polymerization of acrylonitrile can be observed during the chromic acid oxidation of 2,2-dimethyl-l-phenyl-l-propanol. The polymerization is caused by radicals formed during the oxidation of benzaldehyde (which is one of the cleavage product of phenyl-1-butylcarbinol). The oxidation of benzaldehyde is due to the chromium(IV), most probably, or chromiun(V) intermediates. 

Other degradation products of the cytosine moiety were isolated and characterized. These include 5-hydroxy-2 -deoxycytidine (5-OHdCyd) (22) and 5-hydroxy-2 -deoxyuridine (5-OHdUrd) (23) that are produced from dehydration reactions of 5,6-dihydroxy-5,6-dihydro-2 -deoxycytidine (20) and 5,6-dihydroxy-5,6-dihydro-2 -deoxyuridine (21), respectively. MQ-photosen-sitized oxidation of dCyd also results in the formation of six minor nucleoside photoproducts, which include the two trans diastereomers of AT-(2-de-oxy-/j-D-eryf/iro-pentofuranosyl)-l-carbamoyl-4 5-dihydroxy-imidazolidin-2-one, h/1-(2-deoxy-J8-D-crythro-pentofuranosyl)-N4-ureidocarboxylic acid and the a and [5 anomers of N-(2-deoxy-D-eryfhro-pentosyl)-biuret [32, 53]. In contrast, formation of the latter compounds predominates in OH radical-mediated oxidation of the pyrimidine ring of dCyd, which involves preferential addition of OH radicals at C-5 followed by intramolecular cyclization of 6-hydroperoxy-5-hydroxy-5,6-dihydro-2 -deoxycytidine and subsequent generation of the 4,6-endoperoxides [53]. 

The uncatalysed p-coumaric acid oxidation led to the formation of intermediates (not shown here) almost similar to those of the catalysed reaction, without formation of dihydroxylated aromatic compounds, such as 3,4- dihydroxybenzaldehyde. This result shows that the catalyst may promote the hydroxylation of aromatic ring by enhancing the formation of hydroxyl radicals in the reaction mixture. 

During the chain oxidation of hydrocarbons, sulfides and disulfides terminate chains by reacting with peroxyl radicals [40,42,44], which, as opposed to phenols, are weak inhibitors (see Table 17.6). The mechanism and stoichiometry of the termination reaction by sulfides remain yet unclear. Since sulfenic acid is an efficient scavenger of free radicals, the oxidation of tetralin in the presence of dialkylsulfoxide occurs only if the initiation rate v > vimin is proportional to the concentration of sulfoxide [5], so that the rate of oxidation is... 

The present volume deals with the properties of dienes, described in chapters on theory, structural chemistry, conformations, thermochemistry and acidity and in chapters dealing with UV and Raman spectra, with electronic effects and the chemistry of radical cations and cations derived from them. The synthesis of dienes and polyenes, and various reactions that they undergo with radicals, with oxidants, under electrochemical conditions, and their use in synthetic photochemistry are among the topics discussed. Systems such as radialenes, or the reactions of dienes under pressure, comprise special topics of these functional groups. 

Introduction. The production of terephthalic acid (1,4-benzenedicarboxylic acid) has several interesting features. First, it is one of the examples of a homogeneous, radical-catalysed oxidation with the use of dioxygen and cobalt salt initiators. Secondly, it is an example of a catalyst/product separation involving a filtration of the product from the liquid that contains the catalyst. Crystallisation on such a huge scale is not very attractive, but the low solubility of phthalic acid in many solvents and the high boiling point do not allow any other solution. Theoretically, a solvent-solvent extraction would be an option, but we are not aware of a viable combination of solvents. 

Bordwell (Bordwell and Bausch, 1986) has developed a method to determine C—H BDEs from a combination of p ha values and oxidation potentials (E ) of the corresponding anions in dimethyl sulphoxide solution. These acidity-oxidation potentials (AOP) are taken as measures for BDEs and are related to the stabilization of the radicals formed. This procedure has been recently applied to the subject of captodative stabilization (Bord-well and Lynch, 1989). Values of ABZ) relative to the C—H BDE in methane are calculated according to (13). These values are set equal to the... 

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