Theoretical investigation of the anaerobic reduction of halogenated alkanes by cytochrome P-450. 2. Vertical electron affinities of chlorofluoromethanes as a measure of their activity

Abstract

The electron-accenting ability of chlorofluoromethanes is determined by both ab initio and MNDO methods. For the full set of molecules (CH3F, CH2F2, CHF3, CF4, CH3Cl, CH2Cl2, CHCl3, CCl4, CH2FCl, CHF2Cl, CHFCl2, CF3Cl, CF2Cl2, CFCl3), the vertical electron affinity (VEA) is calculated. The VEA is defined as the negative of the energy change on going from the neutral molecule, at its equilibrium geometry, to the metastable anion, leading to dissociative electron attachment, at the same geometry. The geometry of the neutral molecule is totally optimized at the ab initio and MNDO levels. The ab initio optimization uses 3-21G and 6-31G* basis sets. Single-point calculations are performed at the HF/3-21G optimized geometry on a 6-31G* basis with second-order Moller—Plesset perturbation theory. A direct correlation is found between the VEA of a compound and its activity toward reductive metabolism. Of the nine species that have been experimentally examined, these results correctly predict their relative activity and allow a prediction of the activity of the remaining five compounds. © 1988, American Chemical Society. All rights reserved.