BrNO2 is produced by the heterogeneous reaction of ClNO2, highly diluted in He, with an aqueous bromide solution and subsequent trapping at −155 °C. The crude product is purified by trap to trap condensation and fractional sublimation in vacuo. At 300 K and a pressure of 1 mbar, a half-life of about 1 h is observed. The decomposition produces Br2 and NO2. The UV/vis and IR absorption cross sections of gaseous BrNO2 are determined in the ranges 185−600 nm and 2000−400 cm-1, respectively. Irradiation of matrix-isolated BrNO2 with visible light causes nearly quantitative isomerization to trans-BrONO, while ClNO2 is converted by UV light into a mixture of cis- and trans-ClONO. It is possible to assign all fundamentals of BrNO2 and trans-BrONO by comparison to the respective band position of the analogous molecules XNO2 and XONO (X = Cl, F).

The synthesis of FC(O)OONO2 is accomplished by the photolysis of a mixture of (FCO)2, NO2, and O2. The pure product is isolated after trap-to-trap condensation and the removal of byproducts by treatment of the crude product with O3 and AsF5. The colorless liquid freezes at −105 °C; its boiling point is 32 °C. At 20 °C and a few millibars, FC(O)OONO2 decomposes in the gas phase with a half-life of 20 h. FC(O)OONO2 is characterized by vapor pressure measurements, vibrational, 19F NMR, 13C NMR and UV spectroscopies as well as by mass spectrometry. According to the vibrational and NMR spectra, the compound exists at room temperature only as a syn conformer. The molecular structure of FC(O)OONO2 is determined by gas electron diffraction. The molecule possesses a skew structure with a dihedral angle of φ(COON) = 86.2(14)°. The short O−O bond (1.420(6) Å) and the long N−O bond (1.514(6) Å) are consistent with the chemical properties of this compound. The experimental geometry is reproduced reasonably well by quantum chemical.

Ozone is formed in good yield by reacting O2 + salts with water in HF at −78 °C. With isotopically labeled water 17O−16O−16O and 18O−16O−16O can be prepared, and other isotopomers could be made by starting with 17O2 + and 18O2 + precursors. 17O NMR spectroscopy and IR matrix spectroscopy are used for detection and decay of the isotopomers. The 17O or 18O label at the terminal position remains at −78 °C, but at higher temperatures scrambling of the atoms is observed. Under strict monomolecular conditions no scrambling is observed till 450 °C, however. Irradiation of ozone in a 15K argon matrix with λ = 254 nm affords scrambling of the label and formation of oxygen. Irradiation with λ > 420 nm initiates only scrambling with little decay. The possible mechanisms of the atomic scrambling are discussed.

No abstract

The gas phase reaction between BrNO and O(3) at low pressure (<10 mbar) results in the formation of BrNO(2) in about 60% yield. In this manner (15)N- and (18)O-labeled BrNO(2) are prepared. In addition, it is shown that BrNO(2) also forms by the heterogeneous low-temperature reaction between gaseous BrNO and solid sulfuric acid, doped with H(2)O(2). It can be assumed that BrNO(2) may be formed in a similar way under stratospheric conditions. The isotope scrambling in the reaction between BrNO and (18)O(3) as well as in the gas phase equilibrium BrNO + NO(2) right harpoon over left harpoon BrNO(2) + NO are investigated. For the equilibrium constant a lower limit of K(298) >/= 1 x 10(-)(3) is deduced from infrared measurements. A detailed IR and Raman study on BrNO(2) is performed. Photolysis of matrix-isolated BrNO(2) at different wavelengths leads to a mixture of cis- and trans-BrONO. The vibrational data of BrNO(2) (6 fundamentals, 7 combinations), cis-BrONO (5 fundamentals, 1 overtone), and trans-BrONO (4 fundamentals, 8 combinations) as well as the calculated force fields are in excellent agreement with the ab initio values, predicted by T. J. Lee (J. Phys. Chem. 1996, 100, 19847).