The hydrogen abstraction reactions: a multireference Moller-Plesset perturbation (MRMP) theory study

The hydrogen abstraction reactions, namely the reactions of H-2 with OH, trans-N2H2 with H, CH4 with OH, and C2H6 with OH, are studied by multireference Moller-Plesset perturbation theory (MRMP) with a complete active space self-consistent field (CASSCF) reference function. We also examine the performance of density functional theory (DFT) with pure and hybrid functionals. In each case the exoergicity, barrier height, and transition state geometry are calculated. DFT methods fail to produce a comet barrier height for these radical reactions. MRMP gives values for the barrier height and exoergicity that are in reasonable agreement with experiment or an accurate estimate, supporting our use of this method as our 'standard'. (C) 2000 Elsevier Science B.V. All rights reserved.