Nitrogen dioxide, electronically excited, from

The Fixation of Carbon Dioxide and Nitrogen.—As reduced carbon compounds are convenient fuels, the possibility of achieving the reductive fixation of COa in vitro is appealing, if remote. There are very few data on photochemical reactions involving carbon dioxide, for it has no low-lying excited states and has not historically been of much interest to the photochemist. However, what appears to be the first example of photofixation of COa in a non-biological system has been briefly reported.18 Photoirradiation (with a high-pressure mercury lamp) of phenanthrene in the presence of an amine and C02 in a polar solvent (MeaSO or HCONMea) yielded 9,10-dihydrophenanthrene-9-carboxylic acid, in unspecified quantum yield. The mechanism appears to involve formation of COaT by electron transfer from the photoexcited amine, followed by attack of COaT on position 9 of phenanthrene. Similar reductive carboxylation of anthracene, pyrene, naphthalene, and biphenyl was observed. 

The reaction between oxygen atoms and nitric oxide produces a continuum between 400 and 1400 nm from excited nitrogen dioxide. These are significantly lower wavelengths than those of the previously discussed reaction between nitric oxide and ozone. This reaction has been used to determine oxygen atoms in kinetic experiments. As with the oxidation of sulfur monoxide with ozone, oxidation with oxygen atoms produces sulfur dioxide in electronically excited states. In this case, the emission is distributed from 240 to 400 nm with a maximum at 270 nm. 

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