2-苯基苯并噁唑的光解反应

聚对苯撑苯并二噁唑(PBO)纤维对光较为敏感,在紫外光照射下会发生降解.本文研究了该纤维的单体2-苯基苯并噁唑(PO)的初级光化学反应机理.当PO分子吸收一个光子而跃迁到第一激发态后,克服25.59kJ·mol-1能垒而越过过渡态,此时噁唑环打开,且两个苯环形成大约90°的二面角而得到产物,该产物可进一步与空气中的水发生次级反应.计算结果表明在第一激发态上噁唑开环反应很容易,但在基态势能面并没有发现噁唑的开环路径.分子中的原子(AIM)的计算结果与上述分析过程相吻合.

Photolysis Reaction of 2-Phenylbenzo[d]oxazole

The temperature-resilient,high tensile-strength fiber polyp-phenylene benzobisoxazole](PBO)is light-unstable and it degrades under ultraviolet radiation.In this paper we study the photolytic mechanism of the PBO monomer,2-phenylbenzod]oxazole(PO).Following absorption of a photon and excitation into the first excited state(S 1),the molecule overcomes an energy barrier of 25.59 kJ·mol-1 to enter the transition state;the oxazole ring is then opened and both benzene rings form a dihedral angle of about 90°to obtain the product,which undergoes further addition reaction with water.Calculations reveal that ring-opening is easily achieved in the potential surface of S 1.However,the pathway through which the oxazole ring opens in the ground state remains obscure.The topological properties of these compounds are in good agreement with the expected bond orders and the photolytic mechanism.