Bis(trifluoroacetyl) Peroxide, CF₃C(O)OOC(O)CF₃

Pure, highly explosive CF₃C(O)OOC(O)CF₃ is prepared for the first time by low-temperature reaction between CF₃C(O)Cl and Na₂O₂. At room temperature CF₃C(O)OOC(O)CF₃ is stable for days in the liquid or gaseous state. The melting point is −37.5 °C, and the boiling point is extrapolated to 44 °C from the vapor pressure curve log p = −1875/T + 8.92 (p/mbar, T/K). Above room temperature the first-order unimolecular decay into C₂F₆ + CO₂ occurs with an activation energy of 129 kJ mol^-1. CF₃C(O)OOC(O)CF₃ is a clean source for CF₃ radicals as demonstrated by matrix-isolation experiments. The pure compound is characterized by NMR, vibrational, and UV spectroscopy. The geometric structure is determined by gas electron diffraction and quantum chemical calculations (HF, B3PW91, B3LYP, and MP2 with 6-31G* basis sets). The molecule possesses syn−syn conformation (both CO bonds synperiplanar to the O−O bond) with O−O = 1.426(10) Å and dihedral angle φ(C−O−O−C) = 86.5(32)°. The density functional calculations reproduce the experimental structure very well.