New insights into the electrophilic aromatic substitution mechanism of tricyanovinylation reaction involving tetracyanoethylene and N,N-dimethylaniline: An interpretation based on density functional theory calculations

Abstract

The reaction between tetracyanoethylene and N,N-dimethylaniline was extensively studied in early of 1960's. Surprisingly, the role of intermediate species involved in the reaction mechanism is still ambiguous. New density functional theory (DFT) calculations have been performed in order to elucidate such reaction pathways. The electrophilic addition of tetracyanoethylene was computed with a free energy barrier of 79 kJ mol−1. The rate-determining step (RDS) of the reaction was observed during the base-assisted deprotonation process, with a calculated value of 103 kJ mol−1. Finally, for the elimination reaction step was obtained a value at 70 kJ mol−1. A strong influence of the solvent polarity has been corroborating the presence of a polar transition state for the RDS of this reaction. Nonpolar solvent provides a higher relative free energy barrier, which is in agreement with experimental observations.