DISSOCIATIVE ELECTRON-TRANSFER - GAS-PHASE MODEL WITH PREDISSOCIATIONMINIMUM (GM-MODEL) - CONSIDERATION BY AM1 METHOD

The quantum-chemical method AMI was first used for investigating the p rocesses of gas-phase dissociative electron transfer (DET) to the mole cules of alkyl halides RX. The investigated alkyl halides encompassed chlorine, bromine, and iodine derivatives, as well as polyhalogenated compounds. The AM1 method was found to yield realistic results that ag ree with experimental data. According to the postulate of the GM-model (the gas-phase model with a predissociation minimum) that was suggest ed earlier, a predissociation minimum for most of the radical anions [ R-X]radical anion was detected on the potential energy curve. By makin g the AM1 calculation, the effective activation energies of electron t ransfer (E(ae)), the bond rupture in the radical anion (E(ar)), and t he values of intramolecular energy of reorganization lambda(i) were es timated. Certain regularities resulting from the GM-model were establi shed. These are: the E(ae) decrease in the series X Cl > Br > I; the intibate change in the activation energies E(ae) and E(ar); and the l inear relationship between force constants f and f of the R-X bond in the starting molecule and radical anions, with f' invariably less than f.