Theoretical Studies on the Mechanism of Photocycloaddition Reaction Between 6 Azauracil and Acetone

作     者：Fang Decai and Fu Xiaoyuan (Department of Chemistry, Beijing Normal University, Beijing) 

出 版 物：《Chemical Research in Chinese Universities》 (高等学校化学研究（英文版）)

年 卷 期：1990年第6卷第1期

页      面：41-46页

核心收录：

学科分类：07[理学] 0703[理学-化学] 

主　　题：6-Azauracil Acetone Diradical intermediate the T1 state The mechanism of photocycloadditlon reaction Intersystem crossing. 

摘      要：The mechanism of photocycloaddition reaction between 6-azauracll and acetone was studied by using semiemptrical SCFMO AMI method. It was found that this reaction is not a concerted one. The calculated results are as follows:(1) A T1 state exciplex is on the T1 state energy surface; (2) T exciplex as a reactant will proceed along the energy surface of T1 state to form a diradical intermediate. The energy barrier of this reaction step is 63. 6 kJ/mol; (3) The T1 state diradical intermediate happens to be close in energy to the ground state intermediate with a similar geometry. Such a situation turns out to be very favorable for an intersystem crossing (jump from the T, state to the ground state) ; (4) The final product will be formed from the ground S0 state intermediate via an energy barrier 88. 2 kJ/mol.