Oxidation by other species

UV irradiation of CCl, in the presence of ethene and NO results in the formation of some phosgene, although no reaction occurs in the absence of the ethene. The mechanisms involved in this reaction are unknown [726]. 

A report [1800] describing the pyrolysis of tetrachloromethane over degassed charcoal at 

Finally, the action of COF on CC1 can generate phosgene as a by-product (see Chapter 13) [13]. 

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If two or more electrochemical half-cell reactions can occur simultaneously at a metal surface, the metal acts as a mixed electrode and exhibits a potential relative to a reference electrode that is a function of the interaction of the several electrochemical reactions. If the metal can be considered inert, the interaction will be between species in the solution that can be oxidized by other species, which, in turn, will be reduced. For example, ferrous ions can be oxidized to ferric ions by dissolved oxygen and the oxygen reduced to water, the two processes occurring at different positions on the inert metal surface with electron transfer through the metal. If the metal is reactive, oxidation (corrosion) to convert metal to ions or reduction of ions in solution to the neutral metal introduces additional electrochemical reactions that contribute to the mixed electrode. 

Complexation of thiyl radicals with thiolate anions to form disulfide radical anions RSSR" is a well established process in fluid solution. The formation of RSSR" from thiyl radicals and thiols has also been observed in glasses where thiyl radicals were generated through either direct photolysis [9, 93, 94] of the thiol or its oxidation by other species (0 and CI2") formed on 7-irradiation in aqueous glasses [20]. This happens even when basicity of the medium does not allow thiolate anions to exist in appreciable concentrations [95]. A suspected intermediate in this case is the RSS(H)R adduct which deproto-nates under the same conditions, since it is more acidic than the parent thiol [10, 11] ... 

For metal compound categories (e.g.,chromiumcompounds), report releases of only the parent metal. Forexample, a user of various inorganic chromium salts would report the total chromium released in each waste type regardless of the chemical form (e.g., as the original salts, chromium ion, oxide) and exclude any contribution to mass made by other species in the molecule. 

Possel et al. [104] also concluded that DCFH is more sensitive to peroxynitrite oxidation than DHR. Unfortunately, both compounds are oxidized by other reactive species (for example, DCFH by superoxide and DHR by HOC1), and therefore, their use for peroxynitrite detection must be confirmed by the other methods. 

In these reactions, the nitrosating species is N203, which is formed by oxidation of NO (Eqns. 9.1 and 9.2) and acts as a donor of NO+ (Eqn. 9.3), while also undergoing competitive hydrolysis (Eqn. 9.4). Thus, effective ni-trosation requires sufficiently high concentration of the thiol to compete efficiently with hydrolysis of N203. Note that nitric oxide can also be oxidized by other oxidants (e.g., ferric hemoproteins, see below) to form the nitroso-nium ion (NO+), which then reacts rapidly with thiolates (Eqns. 9.5 and 9.6) ... 

A significant fraction of H2S produced by dissimilatory processes will also be oxidized by other reactions (Jprgensen, 1982). These intermediate sulfur species (e.g., elemental sulfur) from H2S oxidation may be enriched in 34S, also contributing to the overall 34S signal of H2S (Fry et al., 1988 Canfield and Thamdrup, 1994). Stable sulfur isotopes in... 

When calcination was performed at 470°C, the sample turns light yellow, indicating the conversion of intermediates probably into oxides and other species, accompanied by further V migration to the gel (Fig. 11c). Luminescence measurements from our laboratory (33) have shown that calcination at 470°C results in complete disappearance of vanadyl porphyrin peaks and appearance of some new excitation peaks which can not be observed in the corresponding excitation spectrum of the EuYV(p)AAAC sample. These data suggest that intermediates exist after calcination and that these species may play a critical role during V migration. 

Table 2.1 lists atmospheric sulfur compounds. The principal sulfur compounds in the atmosphere are H2S, CH3SCH3, CS2, OCS, and SO2. Sulfur occurs in five oxidation states in the atmosphere. (See Box) Chemical reactivity of atmospheric sulfur compounds is inversely related to their sulfur oxidation state. Reduced sulfur compounds, those with oxidation state -2 or —1, are rapidly oxidized by the hydroxyl radical and, to a lesser extent, by other species, with resulting atmospheric lifetimes of a few days. The water solubility of sulfur species increases with oxidation state reduced sulfur species occur preferentially in the gas phase, whereas the (+6) compounds often tend to be found in particles or droplets. Once converted to compounds in the S(+6) state, sulfur species residence times are determined by removal by wet and dry deposition. 

Of the different catalytic coatings tested sample No. 3 did not show any evidence of soot oxidation. Incipient soot oxidation was evident on samples No. 4, 5 (a less steep pressure drop trace increase than sample No. 3). Samples No. 6, 7 (foam) exhibited clearly soot oxidation as their pressure drop trace was decreasing with temperature. All pressure drop decreases with the catalytic filters have been observed above 650°C under oxygen deficient conditions and therefore it can be stated that the soot is oxidized catalytically by other species than oxygen in these experiments. The best catalyst formulation appears to be the combination of reducible oxide/alkali metal and precious metal. 

Several other sensors are available that are based on the vollammelric measurement of hydrogen peroxide produced by cn/.ymailc oxidations of other species of clinical interest. These analytes include sucrose, lactose, ethanol, and i.-lactate. A different enzyme is. course, required for each species. In some cases, cn z.yme electrodes can be based on measuring oxygen or on measuring pi I as discussed in Section 23I--2. 

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