苯并氧化呋咱稳定性和异构化的DFT和 ab initio研究

DFT and ab initio Studies on Stability and Isomerization of Benzofuroxan

运用Ｂ３ＬＹ／６—３１Ｇ（ｄ）密度泛函理论（ＤＦＴ）方法对苯并氧化呋咱、邻二亚硝基苯及其间的异构化反应进行了计算研究。结果表明，苯并氧化呋咱的分子总能量比邻二亚硝基苯的低；由苯并氧化呋咱异构为邻二亚硝基苯的正向反应活化能（Ｅａ＋＝５１.０ＫＪ／ｍｏｌ），与文献实测值（５８．６ｋＪ／ｍｏｌ）较接近，而其逆向反应活化能（Ｅａ＝４.６ｋＪ／ｍｏｌ）很小，从而揭示了苯并氧化呋咱比邻二亚硝基苯更稳定。此外，进行了ＨＦ／３－２１Ｇ、ＨＦ／６—３１Ｇ（ｄ）和ＭＰ２／６－３１Ｇ（ｄ）／／６—３１Ｇ（ｄ）水平下相应的计算，发现Ｂ３ＬＹＰ－ＤＦＴ的结果较ａｂｉｎｉｔｉｏ为优。谐振动频率的Ｂ３ＬＹＰ／６—３１Ｇ（ｄ）计算还支持了邻二亚硝基苯为苯并氧化吱咱“自－自”互变重排反应的中间体。

B3LYP/6-31G(d)-DFT (Density Functional Theory) method has been employed to study benzofuroxan,o-dinitrosobenzene and the isomerization between them. The calculated results with B3LYP/6-31G(d)-Dry show: (1) the molecular total energy of benzofuroxan is lower than that of o-dinitrosobenzene; (2) the activation energy (E_a+ = 51.0 kJ/mol) of forward reaction that benzofuroxan isomerises into o-dinitrosobenzene, is in agreement with the experimental (58.6kJ/mol) provided by reference, and the activation energy (E_a- =4.6kJ/mol) of backward reaction is very small. It is concluded thereby that beazofuroxan is more stable than o-dinitrosobenzene. In addition, the corresponding ah initio calculations at the level of HF/3 - 21G, HF/6 --31G(d) and MP2/6-- 31G(d)//6 - 31G(d) were completed, and it was found that the calculable results by B3LYP-DFT method are superior to those from ab initio calculation. The calculations of harmonic vibrational frequencies with B3LYP/6-31G (d) theoretically supports that o-dinitrosobezene is the intermediate of 'self-self' tautomeric rearrangement of benzofuroxan.