Hydrogen peroxide, protonated

Ca.ta.lysis by Protons. The discovery of hydrogen peroxide hydroxylation of phenol in the presence of strong acids such as perchloric, trifluoromethane-sulfonic, or sulfuric acids allows suppression of all previous drawbacks of the process (18,19). This mode of hydroxylation gives high yields (85% based on H2O2 at phenol conversion of 5—6%). It can be mn without solvents and does not generate resorcinol. Its main advantage rehes on... 

Oxygen Compounds. Although hydrogen peroxide is unreactive toward ozone at room temperature, hydroperoxyl ion reacts rapidly (39). The ozonide ion, after protonation, decomposes to hydroxyl radicals and oxygen. Hydroxyl ions react at a moderate rate with ozone (k = 70). 

Hydrogen peroxide has a rich and varied chemistry which arises from (i) its ability to act either as an oxidizing or a reducing agent in both acid and alkaline solution, (ii) its ability to undergo proton acid/base reactions to form... 

When tertiary butyl hydrogen peroxide (TBHP) was used alone as the radical initiator, no grafting of methylmethacrylate (MMA) onto wool was observed. However, TBHP in conjunction with mineral acids, such as H2SO4, HNO3, or HCIO4 afforded good results [26]. Protonation of TBHP by the acid aided in the dissociation of TBHP to yield free radicals, which initiated grafting reaction. 

Micellar catalysis to enhance or diminish the rate of chemical reactions is well known [97]. Of somewhat greater interest is the influence of micelles on competing reactions, e.g., proton-catalyzed reactions. An example related to the effect of alkanesulfonates is the epoxidation of simple aliphatic olefins. The reaction of olefins and hydrogen peroxide catalyzed by strongly acidic Mo(VI)... 

This concerted reduction by two ferrous species eliminates H02- (or O2 ) as an intermediate and explains the weak catalysis by Cu(II) (which is strong for V([II) and V(IV) autoxidations). Weiss has suggested that the species Fe. 02.Fe may be a stable intermediate, but Wells explains the presence of two Fe(Il) species in the rate law in terms of a pre-existing dimeric form of Fe(lf) containing an H2O bridge, for which there is evidence . The reduction is completed via the Fenton reaction vide infra). The hydrogen peroxide dianion is probably never free but is protonated whilst complexed to Fe(III). 

The resulting unstable molecular ion Oj) rapidly adds another electron and protons to yield hydrogen peroxide. In alkaline solutions the same pathway is followed, but owing to the much lower polarization, the reaction becomes practically reversible (b = 0.03 V) its rate then is determined by oxygen transport to the surface, and polarization is of the concentration type (Bagotsky and Yablokova, 1953). 

Generation of superoxide radical under physiological conditions ultimately leads to the production of hydroxyl radical through a cascade of redox reactions. Initially, sn-peroxide disproportionates to generate hydrogen peroxide (Eq. 3, Scheme 8.36) Superoxide radical exists in equilibrium with its protonated form (H02, = 5). 

D. Dolphin Such potentials refer to free hydrogen peroxide (H2O2). The potentials at which coordinated peroxide can be formed are lower, but subsequent protonation of such coordinated peroxide can result in the liberation of free peroxide which can then react with the periphery of the porphyrin. 

The benzotriazolyl derivative of acrolein acetal, compound 882, is lithiated, treated with chlorodiphenylphosphine, and the obtained intermediate is oxidized with hydrogen peroxide to phosphine oxide 883 (Scheme 145). The relatively acidic proton in derivative 883 is easily removed by a base, and the obtained anion adds to a carbonyl group of aldehyde or ketone. Subsequent rearrangement and elimination of the phosphorane group generates diene 884. For the derivatives of aldehydes (884, R2 = H), (E)-(E) stereoselectivity of the elimination is observed. Acidic alcoholysis of dienes 884 affords esters of P,y-unsaturated carboxylic acids 885 < 1997JOC4131>. 

Since for an endothermic reaction the activation energy E > AH, all such reactions cannot explain the experimental value of the activation energy (see Chapter 4). The following mechanism seems to be the most probable now. Hydrogen peroxide is protonized in a polar alcohol solution. Protonization of H202 intensifies its oxidizing reactivity. Protonized hydrogen peroxide reacts with alcohol with free radical formation. 

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