Radical dinitroalkane dianions from the nitration of nitroalkanes by peroxynitrite.
In alkaline solutions at pH >10, peroxynitrite (ONOO(-)) rapidly and efficiently nitrates aci-nitroalkane anions, RCH=NO(2)(-) (R = H, CH(3), or CH(3)CH(2)), to give the radical dinitrodianions, RC(NO(2))(2)(2-). These anions have been characterized by EPR and have multiplets based on 1:2:3:2:1 pentets consistent with a hyperfine coupling with two equivalent (14)N nuclei of the nitro groups, and the following hyperfine coupling constants, in gauss: R = H, a(N) = 9.96 and a(H) = 1.85; R = CH(3), a(N) = 9.90 and a(H) = 3.22; and R = CH(3)CH(2), a(N) = 9.57 and a(H) = 4.01. Nitration is attributed to the trapping of nitrogen dioxide, formed by ONO-OCO(2)(-) homolysis for the carbon dioxide adduct of peroxynitrite, by the aci-nitroalkane anion. In air, the radical dinitrodianions are oxidized to the monoanions, and the kinetics of its formation is readily followed by UV/vis spectroscopy of the rise in absorption at 380 nm. This report represents the first successful spin trapping of nitrogen dioxide formed from peroxynitrite, and the method may be a useful one for preparing geminal dinitroalkanes.
Arnold
E V
EV
Department of Chemistry, University of Wyoming, Laramie, Wyoming 82071-3838, USA.
Bohle
D S
DS
Hu
Y
Y
D004578:Electron Spin Resonance Spectroscopy; D005609:Free Radicals / Q000737:chemistry; D009566:Nitrates / Q000737:chemistry*; D009595:Nitroparaffins / Q000138:chemical synthesis*
D005609:Free Radicals; D009566:Nitrates; D009595:Nitroparaffins; C039642:peroxynitric acid