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.

中文翻译：

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PhCH2O4CH2Ph：PhCH2O2自反应中间体的理论研究

PhCH2O4CH2Ph 分子作为甲苯气相氧化过程中可能的重要中间体，其结构参数在 CAM-B3LYP/6-311+g(df,pd) 水平，振动频率在 B3LYP-D3(BJ )/6-311+g(df,pd) 能级，CCSD(T)-F12/cc-pVDZ-F12 理论水平下主要异构体之间异构化的势能面。找到了10种PhCH2O4CH2Ph异构体，其中C-O4-C骨架的结构参数与HO4H和C2H5O4C2H5的结构参数接近。然而，由于芳香基团的空间位阻较大，PhCH2O4CH2Ph 具有更开放的几何结构，单个异构体中的键角和二面角更大。同时，似乎OO键和芳基之间的超共轭似乎更强，因为 OO 键长比 HO4H 和 C2H5O4C2H5 中的键长略短。PhCH2O4CH2Ph 异构体的谐波振动频率在这里首次被报道，我们发现 PhCH2O4CH2Ph 中 O4 扭转和 OO/CO 拉伸的频率与 CH3O4CH3 和 C2H5O4C2H5 的频率一致。在异构化过程中，定位了三种过渡态，三种主要异构体之间的热力学平衡可能在环境温度下实现，这涉及能垒的特性。