Relative importance of side reactions in the RLi-acrylonitrile — dimethylformamide system

The probability of interaction of anionically growing poly(acrylonitrile) chains with DMF in the acrylonitrile (AN)-RLi-DMF system was investigated by means of NMR and semiempirical, quantum chemical calculations (MNDO). According to the NMR data, poly(acrylonitrile) synthetized with various ROLi initiators does not contain traces of DMF fragments. Quantum chemical calculations were carried out taking CH 3 -CH 2 CH(CN)-Li as a model compound and simulating the anionic active site of AN. The results obtained show that the interaction of this compound with AN is highly preferred (by 100 kJ/mol) to that with DMF. Qualitatively similar results are related to the butyllithium(BuLi)-AN and BuLi-DMF systems. However, the reaction between BuLi and DMF is exothermic (in contrast to that between the active site of the model compound with DMF). This fact is in agreement with the effective addition of BuLi to DMF in the absence of any competing compound