Abstract:
The research herein investigates two primary methods to synthesize trifluoronitromethane, CF₃NO₂. The first method, a photochemical synthesis, was discovered by the Thrasher group and published in 2002. This photochemical method was the first one-step method for generating CF₃NO₂ and uses trifluoroiodomethane, CF₃I, and nitrogen dioxide, NO₂, as the reactants. This process is initiated by a 420 nm blue light apparatus that splits the C-I bond. The optimization and scale-up of this reaction had not been previously investigated. The production of multiple grams of CF₃NO₂ in a single reaction turned out to be impractical due to the equilibrium of 2 NO₂ with N₂O₄. However, the ideal conditions for the maximum generation of CF₃NO₂ were found to be a total pressure of 0.3 atm, a stoichiometric ratio of 1.1 : 1 of NO₂ : CF₃I, a temperature of at least 55 °C, and a reaction time of 18 hours. Even though this method could not be scaled-up, it still represents the fastest and least expensive method for generating lab quantities of 1-3 grams of CF₃NO₂ via multiple reactions. Because of the aforementioned limitations of the photochemical method, a new method for generating larger quantities of CF₃NO₂ had to be discovered. This new method involves the homolysis of the C-I bond in CF₃I at approximately 200 °C in the presence of NO₂ in a pressure vessel. The increase in reaction temperature allows for the previous limitations due to the 2 NO₂ to N₂O₄ equilibrium to be overcome, allowing for larger quantities, 10-100 grams, of CF₃NO₂ to be produced in a single reaction. This method can be carried out over a large pressure range, 10-60 atm; similar reaction times, 18-24 hours; and with a modest increase in the yield to 35-50%. A detailed kinetics study of this new preparative route was carried out by following both the disappearance of CF₃I and the appearance of CF₃NO₂. The results yielded a C-I bond energy for CF₃I that is in agreement with literature values. A new purification method was also developed for the larger quantities of CF₃NO₂, and the thermal properties of CF₃NO₂ were investigated using an accelerating rate calorimetry (ARC). The molecule CF₃NO₂ was found to be stable to almost 300 °C.
