Wilzbach Tritation studies. III. A study of physical variables affecting exchange in the polycyclic aromatics

Abstract

The effect of particle size of substrate and tritium gas pressure on the efficiency of Wilzbach tritiation of crystalline polycyclic hydrocarbons has been investigated. The hydrocarbons studied included naphthalene, biphenyl, phenanthrene, chrysene, pyrene, m- and p-terphenyls, and acridine. No simple relationship between ionization potential and tritium incorporation was observed. The effect of radical scavengers such as nitric oxide and moderators such as helium on the labelling process have been examined. Tritium incorporation in a polycyclic hydrocarbon is enhanced lf gas exposure occurs in the presence of benzoic acid. The results are discussed in terms of current theories proposed for tritium labelling based on gas-phase studies. In the condensed phase present data show that radical processes are important in Wilzbach labelling. This has been confirmed by a preliminary e.s.r. examination of naphthalene and anthracene in the presence of tritium gas.