Optimization of the photochemical generation of trifluoronitromethane, CF3NO2, and a refined purification technique

The gas-phase photochemical generation of CF3NO2 from CF3I and NO2 was found to be equilibrium limited. The formation of CF3NO2 is favored at low pressure and high temperature, where the concentration of the reactive species NO2 is the greatest, and unfavored at high pressure and low temperature, where the concentration of N2O4 is greatest. The results from varying the stoichiometric ratio of reactants, pressure, temperature, and reaction time in an attempted scale-up of this reaction are consistent with the reaction being equilibrium limited. The best reaction conditions allowed the generation of only 1–3 g of CF3NO2 per batch reaction in an approximate 16-L vessel. As long as reaction conditions are chosen so that all of the starting CF3I is consumed, caustic scrubbing affords a significantly faster, less expensive, and more practical purification method than those previously published.

Graphical abstractThe gas-phase photochemical generation of CF3NO2 from CF3I and NO2 was found to be equilibrium limited. The best reaction conditions allowed the generation of only 1–3 g of CF3NO2 per batch reaction in an approximate 16-L vessel.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Gas-phase photochemical generation of CF3NO2 from CF3I and NO2 is equilibrium limited (i.e., 2 NO2 ⇆ N2O4). ► Lowest stoichiometric excess of NO2:CF3I produces the highest mol% of CF3NO2. ► Scale up of this reaction by increasing the pressure is ineffective. ► At reduced temperatures when little NO2 is present, significant amounts CF3NO2 are not generated. ► Caustic scrubbing gives a significantly faster, less expensive, and more practical method of purification.