Quasi-RRHO approximation and DFT study for understanding the mechanism and kinetics of nitration reaction of benzonitrile with nitronium ion

Abstract

The nitration reaction of benzonitrile with nitronium cation, NO2+, has been studied within the Molecular Electron Density Theory at the MN15-L/aug-cc-pVTZ level of theory. For this electrophilic aromatic substitution (EAS) reaction, three regioisomeric reaction paths have been studied. Quasi-RRHO approximation was applied to consider the vibrational contribution to entropy and correct the Gibbs free energy profile of the reaction in the solvent phase. Benzonitrile is less nucleophilically activated than benzene due to the presence of the electron-withdrawing CN group the meta position is the more favorable reaction path of this EAS reaction. The analysis of ELF and AIM demonstrates that binding of cyanide group to the aromatics ring (CC bond) is strong due to the transfer of electron densities of CN bond and N-atom to the disynaptic basin of this bond.