DFT and ab initio Studies on Stability and Isomerization of Benzofuroxan

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)-DFT show:(1)the molecular total energy of benzofuroxan is lower than that of o-dinitrosobenzene;(2)the activation energy(Ea+=51.0kJ/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(Ea-=4.6kJ/mol)of back-ward reaction is very small.It is concluded thereby that benzofuroxan is more stable than o-dinitrosobenzene.In addition,the corresponding ab 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 calculated 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 supported that o-dinitrosobenzene is the intermediate of “self-self”tautomeric rearrangement of benzofuroxan.