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

Abstract

The geometries of three ClIO isomers and Ðve isomers have been computed at the MP2 \ fc/6-311 ] G(3df ) level of ClIO 2 theory. MP2 \ full/6-31G(d) vibrational frequencies were computed. Gaussian-2 energies and isodesmic reactions were employed to derive for ClIO, ClOI, IClO, ClOIO, ClOOI, IOClO and of 74.7, 82.5, 172.4, 17.0, 113.5, 132.0, 159.9 * f H 298 ClIO 2 , IClO 2 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 via bound intermediates, and a direct path via abstraction. The other products which are exother-I ] ClO 2 mic and capable of being formed without complex rearrangements are ClOIO, ClOOI and OClOI.

Computational Investigations of Iodine Oxides

“…The first steps in standard G2 theory are to compute the geometry at the MP2=FULL/6-31G(d) and the frequencies at the HF/6-31G(d) levels of theory, respectively. Whereas such results are usually in good accord with experimental measurements, as we discussed earlier this is clearly not the case for a test molecule, IO. We have employed MP2=FC/6-311+G(3df) calculations for the geometries because this level of theory gave better accord with the experimental IO bond length than results obtained with smaller basis sets or other electron correlation treatments, including B3LYP and QCISD(T) .…”

“…Whereas such results are usually in good accord with experimental measurements, as we discussed earlier this is clearly not the case for a test molecule, IO. We have employed MP2=FC/6-311+G(3df) calculations for the geometries because this level of theory gave better accord with the experimental IO bond length than results obtained with smaller basis sets or other electron correlation treatments, including B3LYP and QCISD(T) . Frequency calculations at this level are too computationally demanding, and instead MP2=FC/6-31G(d) values scaled by a standard factor of 0.9646 were employed.…”

Kinetics and Mechanism of the Initial Phase of the Bromine−Chlorite Ion Reaction in Aqueous Solution

“…The first X 2 O 2 -type transient species (X = halogen atom) was postulated in 1948 by Taube and Dodgen in their study of the reactions of the chlorite ion with Cl 2 and HOCl. Since then, the formation and subsequent reactions of these reactive intermediates have been in the cores of the mechanisms postulated for aqueous reactions of oxyhalogen species. − Some of the X 2 O 2 species were detected in polycrystalline ice and gas phases, and theoretical discussions of their structures and reactivities were presented. − However, direct experimental evidence to prove the existence of such species in aqueous solutions has not, until now, been found. The primary objective of our present study was to obtain evidence for the formation of BrClO 2 and, if possible, to observe its properties in selected reactions.…”