Computational studies of the isomers of ClIO and ClIO2 Implications for the stratospheric chemistry of iodine

Abstract

The geometries of three ClIO isomers and five ClIO ₂ isomers have been computed at the MP2 = fc/6-311+G(3df) level of theory. MP2 = full/6-31G(d) vibrational frequencies were computed. Gaussian-2 energies and isodesmic reactions were employed to derive Δ _f H ₂₉₈ for ClIO, ClOI, IClO, ClIO ₂ , ClOIO, ClOOI, IOClO and IClO ₂ of 74.7, 82.5, 172.4, 17.0, 113.5, 132.0, 159.9 and 189.8 kJ mol ⁻¹ , respectively. These results were used to assess likely products of the IO + ClO reaction: there are both indirect pathways to I + ClO ₂ via bound intermediates, and a direct path via abstraction. The other products which are exothermic and capable of being formed without complex rearrangements are ClOIO, ClOOI and OClOI.