Theoretical exploration of the potential energy surface of the HOI → HIO isomerization reaction

• Published in: Chemical physics letters 2007-02, Vol.436 (1), p.68-74
• Main Authors: Sun, Q., Mackie, J.C., Dlugogorski, B.Z., Kennedy, E.M.
• Format: Article
• Language: English
• ISSN: 0009-2614; 1873-4448
• DOI: 10.1016/j.cplett.2007.01.049

For one water molecule assisted HOI → HIO isomerization reaction, the activation energy via a mechanism which involves a single water molecule reduces to 48.4 kcal/mol. The isomerization reaction HOI → HIO has been investigated using quantum mechanical techniques. The activation energy of the reaction at the CCSD(T) level of theory is 77.0 kcal/mol. Molecular parameters and relative energies of HOI, HIO, five HOI–H 2O complexes, three HIO–H 2O complexes and four transition states have been calculated by the B3LYP method. For isomerization assisted by a single water molecule, the activation energy whereby the water molecule directly facilitates proton transfer during isomerization, reduces to 48.4 kcal/mol. Where the water molecule interacts with the HOI/HIO system by forming hydrogen-bond and/or van der Waals complexes, the activation energy is not significantly reduced.