Abstract
The electronic and geometric structures of the CH~3~Li/acrylonitrile (AN) and CH~3~Li/2AN systems were investigated by the semiempirical quantum‐chemical MNDO1MNDO: Modified neglect of differential overlap.
method. For the CH~3~Li/AN system a fundamental difference was found between the predictions of the most favourable reaction path (initiation or termination of polymerization) based on the comparison of two intermediate complexes (IC) on the one hand and of two transition states (TS) on the other hand. The lower energy of the TS of initiation reaction as compared to the energy of the TS of termination reaction correlates with the experimentally observed predominance of the initiation reaction. In contrast to this, a comparison of the two IC energies shows no preference of one of the reactions. In the case of the CH~3~Li/2AN system, a comparison of different IC by their energies shows qualitative agreement with experimental data. The results of the MNDO calculations were verified by ab‐initio STO‐3G and 3‐21G calculations. The well‐known enhancement of the termination reactions of anionic active sites (AS) of AN in the stage of trimer AS was interpreted on the basis of geometric and electronic structures of the Li(CH~2~)~5~CN model active sites investigated by the MNDO method.