甲苯基重氮盐及其与冠醚络合物光解活泼自由基的ESR研究

ESR STUDY ON THE FREE RADICAL INTERMEDIATES FORMED DURING THE PHOTOLYSIS OF METHYL PHENYLDIAZONIUM SALTS AND THEIR CROWN ETHER COMPLEXES

本文以2,3,5,6-四甲基亚硝基苯(ND)和苯亚甲基叔丁基氮氧化物(PBN)作自由基捕捉剂研究了甲苯基重氮盐及共冠醚络合物光解的自由基历程。ESR结果表明光解可产生相应的甲苯基自由基,并能被ND或PBN所捕获。由共ESR谱可得到甲基取代苯环上的甲基质子通过超共轭作用产生的超精细裂分,共裂分值与苯环上相同位置质子与未偶电子间极化偶合作用引起的裂分值相近。即:α_(p-)~H≈α_(P-)^(CH):α_(o-)~H≈α_(o-)^(CH)3;α_(m-)~H≈α_(m-)^(CH)3.同时还存在下列关系式:α_(p-)~H≈α_(o-)~H>α_(m-)~H.

Active free radicals formed by the photolysis of methyl substituted phenyldiazonium and their crown ether complexes have been studied by current spin trapps nitrosodurene (ND) and phenyl-t-butyl nitrone (PBN).The ESR results reveal that the methyl substituted phenyl produced therein can be easily trapped by ND and PBN. The hyperfine splitting caused by hyperconjugation interaction of proton in substituted methyl group can be obtained from ESR spectra and their splitting constants are approximately equal to those caused by polarizing couple interaction between unpa(?)red electron and protons in the same ring position, that is to say, a (p-H)≈a (p-CH_3); a (o-H)≈a (o-CH_3); a (m-H)≈a (m-CH_3). For the different ring position, the constants a (H) are in the order of