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E.S.R. study of the free radicals produced by the γ-irradiation of pyridine

par David, Christiane ;Geuskens, Georges ;Verhasselt, A.;Jung, Peter;Oth, Jean Françcois Michael
Référence Molecular Physics, 11, 3, page (257-263)
Publication Publié, 1966

Article révisé par les pairs

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Résumé :

Pyridine and pyridine-d5 have been irradiated with gamma rays at 77°K and the E.S.R. spectra have been studied as a function of temperature up to the melting point of the compounds. The spectra show that at least two radicals are present at 77°K. The spectrum observed at that temperature with pyridine consists of a triplet (splitting 30 G) superimposed on a more complex signal. The same triplet is observed with pyridine-d5 and has been assigned to a radical cation formed by abstraction of an electron from the nitrogen lone pair. As the temperature is raised, the total intensity of the E.S.R. signal decreases and the triplet disappears leaving, in the case of pyridine, a spectrum consisting of eight equidistant lines (splitting 12 G). This spectrum has been assigned to a radical formed by the capture of a hydrogen atom by the nitrogen. It is concluded that the smaller radiochemical stability of pyridine as compared with that of benzene has to be related to the presence of the lone pair electrons of nitrogen. © 1966 Taylor and Francis Group, LLC.