Interaction of FeO+ cation with benzene, aniline, and 3‐methylaniline: DFT study of oxygen insertion mechanism

Abstract

AbstractThe reaction pathways and energetics for oxygen insertion into CH bond in benzene, aniline, and 3‐methylaniline by FeO+ in the gas phase were investigated by means of the DFT methodology with the B3LYP exchange‐correlation functional and 6‐311G** basis set. The main aim of this work was to elucidate the influence of substituents in phenyl ring on stationary points along the energy profile on sextet and quartet surfaces for the reaction of FeO+ with substituted benzenes. The studies show that the amino and methyl groups change the energetics of oxygen insertion by lowering the energy profile along the reaction pathway. The substituents studied in this work facilitate the insertion of oxygen into the aromatic CH bond by stabilizing the intermediate sigma complex (σ‐complex), the amino group being by far more effective. On the other hand, both functional groups increase the activation energy of the rate‐determining step in the gas phase, so that they have unfavorable influence on the kinetics. The comparison of the energy diagrams for the sextet and quartet spin states indicates the dominance of the low‐spin reactivity in oxygen insertion into aromatic CH bond. Aniline and 3‐methylaniline oxidation occurs via electrophilic addition while the conversion of benzene to phenol by FeO+ is mediated by a σ‐complex with mixed radical and cationic character. Present results are also discussed in the context of oxyferryl group reactivity. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008