Nitrite anion electronic structure

Nitro-compounds fRNOj) are isomeric with nitrites, but their electronic structure, excited states and photochemistry are very different. There is no very low-lying (n.jt ) state, and nitroalkanes show n — 3i absorption with a maximum around 275 nm ( —201 mol - cm In cyclohexane solution, nitromethane (CH1NOi) is photoreduced to nitrosomethane(CH,NO, but nitroethane under the same conditions gives rise to a nitroso-dimer derived from the solvent CS.47). The latter process is probably initiated by cleavage of the carbon-nitrogen bond in the nitroalkane. In basic solution (when the nitroalkane is converted to a nitronate anion) irradiation can lead to efficient formation of a hydroxamic acid (S.48), and this reaction most likely proceeds through formation of an intermediate three-mem bered cyclic species. 

The nitrite anion, NO, is isoelectronic with O3, and its N-O bond-lengths of 1.24 A are about 0.04 A longer than a normal N-0 double bond. Resonance between the increased-valence structures (38) and (39), in which atom A is a nitrogen atom, reflects this observation. These structures may also be obtained by spin-pairing the two unpaired electrons that are present for the ground-states of O and NO . The anion NO is isoelectronic with O2, and therefore, its ground-... 

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