REACTIONS OF H-RADICALS WITH AROMATIC HALOGENO COMPOUNDS IN AQUEOUS-SOLUTIONS

The spectroscopic and kinetic data of the short lived intermediates obtained by the attack of H-radicals on fluoro-, chloro-, bromobenzene, benzylchloride and phenethylchloride in aqueous solutions were studied by pulse radiolysis technique. The first three yield cyclohexadienylradicals (k=1-1.5×109 dm3 mol-1 s-1) with characteristic absorption maxima in the region 220-330 nm. In the case of benzylchloride a quantitative abstraction of chlorine by the H-atoms is observed (k=9.5×108 dm3 mol-1 s-1) leading to the formation of the benzylradical (λmax=257, 303, 317.5nm). The attack of H-atoms on phenethylchloride can occur on the aromatic ring forming also a cyclohexadienylradical (k=2.0×109 dm3 mol-1 s-1, λmax=317, 323nm) as well as on the side chain (k=1.5×108 dm3 mol-1 s-1) yielding H2. The intermediates decay according to a second order reaction with k=2 to 4.6×109 dm3 mol-1 s-1. To elucidate reaction mechanisms, steady state radiolysis experiments on the same systems were performed. © 1979 Springer-Verlag.