A quantum mechanical approach to the kinetics of the hydrogen abstraction reaction H2O2 + •OH → HO2 + H2O

Abstract

AbstractThe kinetics of the hydrogen abstraction from H2O2 by •OH has been modeled with MP2/6‐31G*//MP2/6‐31G*, MP2‐SAC//MP2/6‐31G*, MP2/6‐31+G**//MP2/6‐31+G**, MP2‐SAC// MP2/6‐31+G**, MP4(SDTQ)/6‐311G**//MP2/6‐31G*, CCSD(T)/6‐31G*//CCSD(T)/6‐31G*, CCSD(T)/6‐31G**//CCSD(T)/6‐31G**, CCSD(T)/6‐311++G**//MP2/6‐31G* in the gas phase. MD simulations have been used to generate initial geometries for the stationary points along the potential energy surface for hydrogen abstraction from H2O2. The effective fragment potential (EFP) has been used to optimize the relevant structures in solution. Furthermore, the IEFPCM model has been used for the supermolecules generated via MD calculations. IEFPCM/MP2/6‐31G* and IEFPCM/CCSD(T)/6‐31G* calculations have also been performed for structures without explicit water molecules. Experimentally, the rate constant for hydrogen abstraction by •OH drops from 1.75 × 10−12 cm3 molecule−1 s−1 in the gas phase to 4.48 × 10−14 cm3 molecule−1 s−1 in solution. The same trend has been reproduced best with MP4 (SDTQ)/6‐311G**//MP2/6‐31G* in the gas phase (0.415 × 10−12 cm3 molecule−1 s−1) and with EFP (UHF/6‐31G*) in solution (3.23 × 10−14 cm3 molecule−1 s−1). © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 37: 502–514, 2005