Systems with Participation of Nitrogen Dioxide

3-hexafluoropropan-2-ol, the reaction of l,4-dimethoxy-2,3-dimethylbenzene with a deficit of nitrogen dioxide gives a high concentration of the aromatic cation-radical, which lives long enough and can be detected spectroscopically. In the presence of excessive amounts of N02, this cation-radical decays rapidly giving the 5-nitro derivative of the starting compound (Eberson etal. 1996). 

Kinetic characteristics are obtained for the reaction between several polycyclic aromatic hydrocarbons with nitrogen dioxide in dichloromethane at 25°C. They are in accord with the intermediate formation of the cation-radicals (Pryor et al 1984). 

Considering nitration with the help of NO2/N2O4 in an aprotic medium, one should avoid a simplified approach to its mechanism. The dissociation equilibrium N2O4 = 2NO2 is characterized at 298.15 K (25°C) with constants, on molality basis, 3.5 X 10 in hexane, 5.9 X 10 in carbon tetrachloride, and 5.3 X 10 in chloroform (Mendiara and Perissinotti 2003). In aprotic mediums, two ionic routes of dissociation of N2O4 are possible 

In the presence of water (even in traces), acids are generated 

The acidity constants of HNO3 and HNOj are the following pK lMNOj) = 16.0 and pK (HNOj) = 20.6 at 30°C in sulfolane (Boughriet et al. 1987). The authors deduced the equilibrium constants (K) for N2O4 and NjOj reactions  

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