Properties of Chloroformyl Peroxynitrate, ClC(O)OONO2

The synthesis of ClC(O)OONO2 is accomplished by photolysis of a mixture of Cl2, NO2, and CO in large excess of O2 at about -70 °C. The product is isolated after repeated trap-to-trap condensation. The solid compound melts at -84 °C, and the extrapolated boiling point is 80 °C. ClC(O)OONO2 is characterized by IR, Raman, 13C NMR, and UV spectroscopy. According to the IR matrix spectra, the compound exists at room temperature only as a single conformer. The molecular structure of ClC(O)OONO2 is determined by gas electron diffraction. The molecule possesses a gauche structure with a dihedral angle of (phi)(COON) = 86.7(19)°, and the C=O bond is oriented syn with respect to the O-O bond. The short O-O bond (1.418(6) (angstrom)) and the long N-O bond (1.511(8) (angstrom)) are consistent with the facile dissociation of ClC(O)OONO2 into the radicals ClC(O)OO and NO2. The experimental geometry of ClC(O)OONO2 is reproduced reasonably well by B3LYP/6-311+G(2df) calculations, whereas the MP2 approximation predicts the N-O bond considerably too long and the dihedral angle too small.