A phase-space method for arbitrary bimolecular gas-phase reactions: Application to the CH3CHO+HOand CH3OOH+HOreactions

A new method based upon phase-space methods presented in Ref. [1] (Gross, A .; Mikkelsen, K. V, Stockwell, W. R. Int J Quantum Chem 2001, accepted) has been tested on the reactions CH3CHO + HO --> CH3CO + H2O and CH3OOH + HO - -> products. The method has been used to calculate cross sections, and rate constants in the temperature range 200-550 K. The method requires knowledg e of the system's reaction and product channels for the interacting species , the vibrational frequencies, the moments of inertia, and the potential en ergies of the molecules in their ground state equilibrium configuration. Fu rthermore, the long-range potential between the reactant and product specie s is required. Due to the lack of experimentally determined spectroscopic d ata and potential energies for the reactants and products, these values hav e been calculated using electronic structure theory. We have used the many- body second-order Moller Plesset perturbation theory (MP2) for the treatmen t of electron correlation in the molecules, together with two different Gau ssian-type orbital (GTO) basis sets 6-31G and 6-31G*. The calculated rates are compared with the experimental data estimated earlier elsewhere. On the basis of our limited tests, the method appears to yield rate constants tha t are within a factor of 10-25 at 300 K of the true value, which is much mo re accurate than currently used empirical estimation methods. (C) 2001 John Wiley & Sons, Inc.