对-二氮杂萘 N,N′-二氧化物光解产物的 ESR 研究

STUDIES ON THE PHOTOLYSIS OF HETEROCYCLIC N,N'-DIOXIDES BY ELECTRON SPIN RFSONANCE

芳香 N-氧化物在光激发下发生脱氧、重排、环扩大和环缩小等反应.但 N-氧化物的初级光化学反应是否涉及自由基中间体的过程却未见文献报道.本文利用电子自旋共振技术研究两种对-二氮杂萘 N,N′-二氧化物(1,2)在光解过程中所生成的自由基中间体.

The radicals generated photolytically from heterocyclic N,N′-dioxides have beenstudied by ESR,It is shown that the two C=N double bonds in the N,N′-dioxidesundergo a photochemical transfer,leading to the formation of nitroxide biradicals frombinitrones and the biradicals so formed may abstract hydrogen from the solvent CHCl_3giving monoradicals.The transfer of C=N bond occurs only through irradiation.The temperaturedependences show that the intensities of spectra which corresponding to radical concen-tration did not increase with increasing temperature up to 80℃.It is suggested thatthe first step in photoinduced rearrangement of heterocyclic N,N′-dioxides is theformation of the dioxide biradical from binitrones.