Nitration of styrenes by dinitrogen pentoxide in dichloromethane

The reaction of 4-R-substituted styrenes (R = H, Me, Cl, CF3, NO2) with N2O5 in dichloromethane gives several products including 1-aryl-2-nitroethyl nitrate 1, 1,2-dinitro-1-arylethane 2, 1,2-dinitrato-1-arylethane 3 and 2-aryl-2-nitroethyl nitrate 4. When R = CF3 or NO2, 1-4 are the only products and 1 predominates at low temperature and/or high concentrations of N2O5. All are formed in part by radical pathways, as is shown by N-15 CIDNP effects. Evidence for ionic pathways is also presented. The kinetics of formation of 1 from 4-nitrostyrene at -45 degrees C are of high order in N2O5.