Mechanism oxygen definition

An especially interesting case of oxygen addition to quinonoid systems involves acidic treatment with acetic anhydride, which produces both addition and esterification (eq. 3). This Thiele-Winter acetoxylation has been used extensively for synthesis, stmcture proof, isolation, and purification (54). The kinetics and mechanism of acetoxylation have been described (55). Although the acetyhum ion is an electrophile, extensive studies of electronic effects show a definite relationship to nucleophilic addition chemistry (56). 

Dediazoniation does not show a significant solvent isotope effect ( h2o/ d2o = 0.98 0.01 Crossley et al., 1940 Swain et al., 1975 a). This result is definitely not consistent with a mechanism in which charge is built up on oxygen in the rate-limiting transition state, as expected for an ANDN-like process. 

Let us consider the mechanism (85) for definiteness. The mechanism (86) yields the same result, as can be demonstrated. We denote by Poa and PH2o the partial pressures of oxygen and water vapours. If the reaction takes place in the liquid phase, the partial pressures must then be replaced by the corresponding concentrations. The surface concentrations of the chemisorbed 0 and H atoms and H02 complexes are denoted by No, Nn and Nkoi, respectively. Let N+h, N 0, N hos, N°h and N°o be the surface... 

Now, we may consider in detail the mechanism of oxygen radical production by mitochondria. There are definite thermodynamic conditions, which regulate one-electron transfer from the electron carriers of mitochondrial respiratory chain to dioxygen these components must have the one-electron reduction potentials more negative than that of dioxygen Eq( 02 /02]) = —0.16 V. As the reduction potentials of components of respiratory chain are changed from 0.320 to +0.380 V, it is obvious that various sources of superoxide production may exist in mitochondria. As already noted earlier, the two main sources of superoxide are present in Complexes I and III of the respiratory chain in both of them, the role of ubiquinone seems to be dominant. Although superoxide may be formed by the one-electron oxidation of ubisemiquinone radical anion (Reaction (1)) [10,22] or even neutral semiquinone radical [9], the efficiency of these ways of superoxide formation in mitochondria is doubtful. 

Rossmann, R., Sawers, G. and Bock, A. (1991) Mechanism of regulation of the formate-hydro-genlyase pathway by oxygen, nitrate, and pH Definition of the formate regulon. Mol. Microbiol., 5, 2807-14. 

The chemiluminescence emission resulting from the oxidation of luminol (5-amino-2,3-dihydro-l,4-phthalazinedione) has been extensively studied since its discovery by Albrecht in 1928. Although luminol oxidation is one of the most commonly applied chemiluminescent reactions, to date no definitive mechanism is known . Efficient chemiluminescence emission is only observed when luminol (25) is oxidized under alkaline conditions. Depending on the medium, co-oxidants are required in addition to molecular oxygen for the observation of light emission, but under any condition, 3-aminophthalate (3-AP) and molecular nitrogen are the main reaction products (equation 10). 

When K[PtX(acac)2] (X = Cl, Br) is treated with a strong proton add the uncoordinated 0,0 site is protonated and complex (170) is formed.1606,1607 If the alkyl groups on the 0,0 -bonded acac ligand are non-equivalent, exchange can be observed. Although the mechanism has not been definitively proven, a dissociative mechanism is favored.160 This proposal correlates with the observations that the 0,0 -bonded chelate complex Pt(acac)2 will react with tertiary phosphines and nitrogen bases with substitution of one of the oxygen-bonded chelate arms.1609,1610 A variety of products are formed as outlined in Scheme 17. 

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