利用ESR技术研究α-蒎烯,β-蒎烯光敏氧化反应机理

本文主要利用电子顺磁共振(ESR)自旋捕获技术研究9,10 二氰基蒽(DCA)敏化α-蒎烯(αP),β-蒎烯(βP)光氧化反应.提供了在乙腈中α-蒎烯和β-蒎烯的光氧化反应过程中存在超氧负离子基(O₂^-)和单重态氧(¹O₂)的直接证据;在四氯化碳溶剂中只捕获到¹O₂;在正己烷中没有捕获到O₂^-或¹O₂.ESR实验结果进一步证明在乙腈中光敏氧化反应的¹O₂可能来自O₂^-和反应底物α、β-蒎烯正离子自由基之间的电荷复合(CR).

STUDIES ON THE MECHANISM OF PHOTOSENSITIZED OXIDATION OF -PINENE,-PINENE BY MEANS OF ESR TECHNIQUE

In this work, the mechanism of sensitizedphotooxidations of pinene and pinene by 9,10dicyanoanthracene(DCA) were studied by means of electron spin resonance(ESR) spin trapping method, and 5,5dimethylpyrrolineNoxide(DMPO), 2,2,6,6tetramethylpiperidine(TMP) and tbutylNoxide (tBN) were respectively used as trapping media to trap O2- ,1O2 and carbon center radicals producted in reactions. In acetonitrile, the existence of O2-,1O2 and carboncenter radicals was directly confirmed in ESR experiments;1O2 was only detected in carbon tetrachloride solution; no ESR signals were detected in nhexane solution. The results of ESR experiments show that the sensitized photooxidations is competitive reactions among O2,1O2 and carboncenter radicals, and 1O2 comes from the charge recombination(CR) between O2 and or pinene cation radical in acetonitrile solution, and indicate that the photooxidation undergoes the mechanism of oxidation of 1O2 in carbon tetrachloride solution and 1O2 comes from different mechanism in acetonitrile and carbon tetrachloride, but no DCA sensitized oxidation occurs in nhexane solution.