Theoretical study of PhCH2O4CH2Ph: intermediate in the PhCH2O2 self-reaction

Abstract

As a possible important intermediate during the oxidation of toluene in gas phase, the PhCH2O4CH2Ph molecule has been invested on the structural parameters at CAM-B3LYP/6-311+g(df,pd) level, the vibrational frequencies at B3LYP-D3(BJ)/6-311+g(df,pd) level, and the potential energy surface of isomerization between main isomers at CCSD(T)-F12/cc-pVDZ-F12 level of theory. Ten PhCH2O4CH2Ph isomers were located, in which the structural parameters of C-O4-C skeleton are close to those in HO4H and C2H5O4C2H5. However, due to larger steric hindrance of aromatic groups, PhCH2O4CH2Ph has a more open geometry with larger bond angles and dihedral angles in individual isomers. Meanwhile, it seems that the hyperconjugation appears to be stronger between the O-O bonds and aromatic groups, since the O-O bond lengths are slightly shorter than those found in HO4H and C2H5O4C2H5. Harmonic vibrational frequencies of PhCH2O4CH2Ph isomers were first reported here and we found that the frequencies of O4 torsion and O-O/C-O stretches in PhCH2O4CH2Ph are consistent with those of CH3O4CH3 and C2H5O4C2H5. In the progress of isomerization, three transition states were located and a thermodynamic equilibrium between three main isomers may achieve at ambient temperature concerning the characters of energy barrier.