Dissociations, oxides

Et2NCS)3Mo(NS)], but this reaction s not general. An alternative to direct metathesis with [SN]+ is dissociative oxidative addition (e.g. [MCl2(PPh3)2] + 1/3(S3N3C13) -->... 

The action of uncouplers is to dissociate oxidation in the respiratory chain from phosphorylation. These compounds are toxic in vivo, causing respiration to become uncontrolled, since the rate is no longer limited by the concentration of ADP or Pj. The uncoupler that has been used most frequently is 2,4-dinitrophenol, but other compounds act in a similar manner. The antibiotic oligomycin completely blocks oxidation and phosphorylation by acting on a step in phosphorylation (Figures 12-7 and 12-8). 

Four methods are used for generating pools of these onium ions oxidative C-H bond dissociation, oxidative C-Si bond dissociation, oxidative C-S bond dissociation, and oxidative C-C bond dissociation (Scheme 3). In the following sections, we will discuss the principles and synthetic applications of these methods. 

Alkoxycarbenium ion pools can also be generated by oxidative C-C bond dissociation. Oxidative C-C bond dissociation is well known in the literature.38 Thus, the electrochemical oxidation of l,2-dimethoxy-l,2-diphenylethane 32... 

As an aside, it should be noted that a large intrinsic ET barrier does not necessarily imply an increase of the bond length upon radical anion formation. A substantial angle deformation also may contribute to the internal intrinsic barrier, AGqj. This was shown in the case of the stepwise dissociative oxidation of oxalate ( O2C-CO2 — 02C-C02 4-e—CO2-F CO2 ), where the data suggest that the oxalate undergoes a substantial increase of... 

Saturating the electrolyte with iron(lll) hydroxide (e.g., by addition of aqueous solutions of ferric nitrate) and simultaneously adding cobaltous salts leads to in situ formation of a mixed Fe(llI)/Co(ll)/Co(IIl) deposit, which exhibits catalytic activity comparable to that of Fe304 shown by the current voltage curve in Fig. 11. Such mixed oxidic catalyst coatings are composed of very small oxide crystals, which evidently are dissolved upon current interruption due to dissociative oxide dissolution. The transfer of dissolved metal ions to the cathode followed by cathodic deposition of the metal, however, can be completely prohibited, if the potential of the cathode due to optimal electrocatalysis of cathodic hydrogen evolution proceeds with an over-... 

Recently, Thom has found that several dK iridium compounds undergo (after ligand dissociation) oxidative addition to H2C=0 (generated from paraformaldehyde). Thus obtained were the formyl hydrides shown in Eqs. (12) and (13) (67). These compounds are thermally robust (dec s=130°C) and will undoubtedly be the object of additional study. 

The present view is that cytochrome a is the acceptor of electrons from cytochrome c, but that a simple linear electron-transfer sequence from cytochrome a to Cua and then to the cytochrome 03/Cub centre is unlikely. Instead the sequence shown in equation (63) holds, where cytochrome a is in rapid equilibrium with Cua. These views depend largely upon pre-steady-state kinetics of the redox half reactions of the enzyme with its two substrates, ferrocytochrome c and O2. However, these conclusions are not in accord with kinetic studies under conditions when both substrates are bound to the enzyme, and which show maximal rates of electron transfer from cytochrome c to O2. In particular some of the cytochrome c is oxidized at a faster rate than a metal centre in the oxidase. In contrast, at high ionic strength conditions, where the cytochrome c and the cytochrome oxidase are mainly dissociated, oxidation of cytochrome c occurs only slowly following the complete oxidation of the oxidase. These results for the fast oxidation of cytochrome c have been interpreted in terms of direct electron transfer from cytochrome c to the bridged peroxo intermediate involving 03 and Cub, or to a two-electron transfer to O2 from cytochromes a and 03 during the initial phase of the reaction. 

Free carbon sites may be non-existent and so [Cf] is replaced by [-C(O)], hence second order with respect to this stable oxide. In the model the concentration of dissociated oxides are taken as the concentration of [-C(O)] resulting from step (4). Thus the difference between the area under the curve representing P3 minus the area of the CO curve indicates either the extent of step (5) if the CO area is greater than the P3 area or the availability of -Cf for step (6) if the CO area is less than the P3 area. 

Taking into account the incomplete dissociation of metal oxides in ionic melts, the complete oxide solubility ( sMe0) can be represented by the sum of the activities (concentrations) of metal cations and non-dissociated oxide ... 

The calculations show, however, that the solubilities of metal-oxides in the melts based on alkali-metal halides are considerably lower than the values predicted by the Le Chatelier-Shreder equation, i.e. the properties of the oxide solutions are characterized by negative deviations from ideality. This is caused by the fact that the sum of the interaction energies of the dissolved substance-dissolved substance system (non-dissociated oxide, Me2+-02 )... 

The data on the solubility of CaO and ZnO in the chloride melts allow us to trace the effect of the acidic properties of the melt-constituent cation on the metal-oxide solubilities the ratio of the solubilities in K+, Na+ and Li+-based melts is 1 1.5 15. However, these are the total solubilities, and the data are distorted by the contribution of an appreciable concentration of non-dissociated oxide, which is not sensitive to changes in the melt-acidity. It should be emphasized that since we do not know the ratios of the ionized fraction to the non-dissociated one in all the melts studied, we cannot estimate quantitatively the oxoacidic properties of all the melts in question. This neglect of the metal-oxide s dissociation is because the said work was published in 1923, whereas the Lux definition was formulated only in 1939. Therefore, the authors of Ref. [327] did not take into account the dissociation of the oxides in the molten salts, which from our point of view, reduced the significance of this investigation. 

Since the concentration of the non-dissociated oxide in the saturated solution, as a rule, is hardly determined, for practical purposes the solubility product, the magnitudes of PMeO (used below pP -logP),... 

The carry-over of corrosion product radionuclides with the main steam in the direction of the turbine is effected, on the one hand, by droplet entrainment with the residual moisture content of the steam and, on the other, by steam volatility. Usually, droplet carry-over is the most significant transport mechanism however, the oxides of the primary system metals show a measurable solubility in steam even at BWR operating conditions. At different plants, concentrations of dissolved cobalt on the order of 60 ng/kg were measured in condensed samples of main steam, i. e. significantly higher than could be explained by droplet entrainment (e. g. Hepp et al., 1986). These observations are consistent with the fundamental results on steam volatility of weakly dissociated compounds under BWR operating conditions which were reported by Styrikovich and Martynova (1963). Since only non-dissociated substances are volatile with steam, it has to be assumed that a fraction of the cobalt present as dissolved ions in the reactor water at ambient temperature is converted to non-dissociated oxide, hydroxide or ferrite at the plant operating temperature. 

Chemisorption and Dissociation (Oxidative Addition) of H2 to Transition Metal Atoms 358... 

Vaporization of Cuprous Oxide and Other Dissociating Oxides... 

The behavior of dissociating oxides at high temperatures is briefly reviewed. At low pressures the composition of the oxide will correspond to an equilibrium oxygen pressure quite different from the ambient oxygen pressure. Evaporation rate studies on cuprous oxide in various atmospheres show that this oxide dissociates according to CuiO (solid) — 2Cu (gas) + iOi (gas). 

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