Nitrogen oxides cations from

Conversion of toluenes to the benzoic acid is also accomplished by anodic oxidation in acetic acid containing some nitric acid. It is not clear if this reaction involves the aromatic radical-cation or if the oxidising agents are nitrogen oxide radicals generated by electron transfer from nitrate ions [66, 67]. Oxidation of 4-fluorotoluene at a lead dioxide anode in dilute sulphuric acid gives 4-fluorobenzoic acid in a reaction which involves loss of a proton from the aromatic radical-cation and them in further oxidation of the benzyl radical formed [68]. 

The pH of precipitation that has absorbed S02 or sulfates will depend on the other ions present, which can include N03" formed from nitrogen oxide emissions and base cations from various dust sources, as well as HC03 from atmospheric C02 and organic acids from natural sources. Precipitation with pH values below 5.6 (the value for equilibrium with atmospheric C02) is popularly referred to as "acid rain."... 

Arylcyclopropanes and their heterocyclic analogues are liable to electron transfer induced fragmentation of a carbon-carbon bond that in some cases leads to synthetically useful products. Thus, 1,2-diarylcyclopropanes [240-243] as well as 2,3-diaryloxirans [244-246] and -aziridines (in the last case, also 2-monophenyl derivatives) [247,248] are cleaved upon photoinduced electron transfer sensitization. The final result, after back electron transfer, is trans-cis isomerization of the ring. In the presence of a suitable trap, however, a cycloaddition reaction takes place, involving either the radical cation or the ylide. Thus, dioxoles, ozonides or azodioxoles, respectively, are formed in the presence of oxygen and oxazolidines have been obtained from cyclopropanes in the presence of nitrogen oxide (Sch. 23). 

Fig. 1.94. Catalytic cycles for the homogeneous reduction of nitrogen oxides by carbon monoxide mediated by various atomic transition metal cations M+. The ions Fe+, Os+, and lr+ were found to be most effectively performing the outhned reaction cycles out of 29 investigated transition metal elements. Adapted from [462]...

FIGURE 4.34 Proposed electrochemical processes occurring on the MojC-derived carbon electrode at high positive polarizations in [EMIMJCBFJ electrolyte (a) oxidative dimerization of EMIM+ cations via N-N bond formation (b) possible complexation of in situ elec-trochemically formed BF3 with a free electron pair of a nitrogen atom in the EMIM cation and/or the substitution of an alkyl chain to the EMIM+ cation. (From Kruusma, J. et al. 2014. In situ XPS studies of electrochemically positively polarized molybdenum carbide derived carbon double layer capacitor electrode. Journal of the Electrochemical Society, 161 A1266-A1277. Reproduced by permission of The Electrochemical Society.)... 

Common impurities include those formed in reformate fuel streams (carbon oxides (COx), methane (CH4), hydrogen sulfide (H2S), and ammonia (NH3)), pollutants found in air (sulfur oxides (SOJ, nitrogen oxides (NOJ, ammonia (NH3), and organic compounds (propane, benzene, toluene)), catalyst fines carryover, rust from piping, salts, and dust. Impurities may adsorb onto the Pt surface (CO, H2S, SO, and CP), carbon support (H2S and SOJ, or gas diffusion layers (salts, dust, and organic compounds), and adsorb into the ionomer (silica, cations (M+), NH4" ), or simply plug up the flow passages. 

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