Photochemistry nitrogen dioxide

Nitrogen dioxide Nitrate Nitrite Ozone Photochemistry Quantum yield Rate law... 

The generation of ozone in the troposphere depends on the photochemistry of nitrogen dioxide, NO2 ... 

Ozone Most chemical species in the atmosphere are oxidized, a process that is tri ered mostly by the hydroxyl radical (OH-) and the ozone molecule (O3). Both oxidants are produced by atmospheric photochemistry, with the dominant source reaction being the photolysis of nitrogen dioxide (NO2), followed by combination with molecular oxygen ... 

Nitrogen oxides play an important role in the photochemistry of the troposphere, controlling the formation of tropospheric O3, affecting the concentration of the hydroxyl radical, and contributing to acid precipitation. Nitrogen dioxide (NO2) is one of the most important reactive nitrogen species its photolysis is the primary source of O3 in the troposphere (see Section 28.6 for further details on the actual chemical processes and rates). 

The formation of oxygen atom 0( P) in the photolysis of nitrogen dioxide (NO2) is the fundamental reaction that causes direct production of O3 in the troposphere. In this section, absorption spectrum and 0( P) production quantum yields relevant to the tropospheric photochemistry are described. 

Topics that have formed the subjects of reviews this year include contemporary issues in electron transport research, dynamics of bimolecular photoelectron transfer reactions, photophysical properties of functionalised fullerene derivatives, carbon-carbon bond formation via radical ions, photoinduced electron transfer processes in ketone, aldehyde, and ester synthesis, photochemical reactions between arenenitriles and benzylic donors, photo-oxidation of conjugated dienes, photoredox reactions of aromatic nitro compounds, electron transfer-mediated photochemistry of some unsaturated nitrogen-containing compounds, reactions of 02( Ag), carbon dioxide activation by aza-macrocyclic complexes, and photochromism of chalcone derivatives. ... 

As for photochemistry, aliphatic amines are photodegraded over titanium dioxide, and the nitrogen is found mainly as ammonium cation. The complex issue of H elimination from aminoacids has been confronted by experiments and computation, a recent example referring to phenylalanine and derivatives. A detailed mechanistic analysis of the H loss from aniline... 

Early investigatioiis of the photochemistry of a-heteroatom substituted carboxylates 40 (Scheme 19) concentrated on the operation of SET processes. These substances possess two potential electron donor sites. SET from the carboxylate moiety leads to formation of an acyloxy radical 41 while SET from the heteroatom center gives rise to a zwitterionic radical 42. Subsequent loss of carbon dioxide from either of these intermediates yields the same carbon-centered, heteroatom-stabilized radical 43. The critical factors determining which of these pathways is responsible for the SET-promoted decarboxylation reactions of substrates in this family is (1) the relative oxidation potentials of the two potential donor moieties and (2) the relative rates of decarboxylation of intermediates 41 and 42. Redox potential data indicate that electron transfer from sulfur (E(-t) = ca. 0.4 V) and nitrogen (E(-l-) = ca. 0.7 V) centers to acceptors should be thermodynamically more favorable than from carboxylate groups (E(-t) = ca. 1.4 V). 

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