US EPA

8631751 

Journal Article 

Radiolytic preparation of radical cations of nitroalkanes and related compounds 

Rao, DNR; Symons, MCR 

1985 

1 

Journal of the Chemical Society, Faraday Transactions 1: Physical Chemistry in Condensed Phases
ISSN: 0300-9599 

81 

3 

565-578 

English 

10.1039/F19858100565 

Exposure of dilute solutions of a range of organic nitro derivatives in trichlorofluoromethane to 60Co γ-rays at 77 K gave radical cations thought to be formed from the expected primary species by some form of relaxation. These cations have e.s.r. spectra similar to that of nitrogen dioxide, and may be the isomeric nitrite cations, ROṄO+. However, the form and magnitude of the 13C hyperfine coupling for cations derived from 13CH3NO2 suggests that the alternative σ-structure (R.NO2)+ may be a better description. Cations derived from CH3CH2NO2, CH3CH2CH2NO2, (CH3)2CHNO2, (CH3)3CHO2, (CH3)2C(Cl)NO2, (CH3)2C(Br)NO2, (CH3)2C(CO3Et)NO2 and [(CH3)2CNO2]2 all had very similar e.s.r. spectra, with indications of extra hyperfine splitting from halogen nuclei for the chloro and bromo derivatives. The ethyl derivative was unique in giving a second species in comparable yields which exhibited very large hyperfine coupling and considerable g-value variation. This is tentatively identified as CH3CH2O. radicals complexed with NO+ cations. The ethyl ester derivative gave a second species thought to be the ester cation. Several nitro aromatic compounds gave the normal π-cations initially, but all gave evidence for the rearranged NO2-like cations on annealing. A derivative ArC(Me)2NO2 with a p-nitro group gave high yields of this NO2-like cation even at 77 K, with no sign of the π-aromatic cation. One vinyl derivative, 1-nitrocyclohexene, was also studied. This gave a complex spectrum which is assigned to a cation with its SOMO primarily confined to the alkene group. However, conversion into the rearranged cation was again detected on annealing.