The reactions of radioactive chlorine atoms recoiling from two nuclear processes, "Cl(n, 2n)"'"a and "Cl(n, 7)"CI have been studied in different liquid halobenzenes. The ratio "Q-for-Cl vs.^'Cl-for-H yield for C^HjCl is dose-dependent, indicative for radiation-enhanced ^' Cl-for-Cl exchange. The Cl-for-Cl replacement yield is lowered on the addition of Ij, but much more for "CI than for It is suggested that the precursors to the exchange is a charge-transfer 7r-complex, rather than a a-complex. The fraction of the * Cl-for-Cl replacement yield not affected by Ij is ascribed to direct hot one-step processes. The behaviour of m-Cj H4 Clj is different to the extent that -as measured for 34 mQ _ thermal exchange seems to take place. Also, isomeric dichlorobenzenes irradiated in a mixture show differences among each other in exchange behaviour. Part of the unidentified products is attributed to an excited jr-complex subject to ring-opening and/or fragmentation. The ""'Cl vs."Cl isotope effect is not due to external radiation and is discussed in terms of differences in the recoil energy distribution and the life-time of lower levels of nuclear excitation.

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Recoil chlorine ¡Chlorotoluenes /Hot atom chemistry /Ipso attack AbstractThe chemical reactions of recoil 38 C1 atoms have been studied in liquid ortho, meta and para chlorotoluenes and in a 1 :1:1 mixture. In the pure liquids, the total organic yield is less in meta isomer compared to ortho and para isomers and is mainly due to a lower 3 * Cl-for-Cl substitution yield. In systems scavenged with 2 mol % I,, these substitution yields are about same for each of the three isomers. In a 1 :1 :1 mixture of the o : m : ρ isomers, containing 2 mol % I 2 , the ratios of the (hot) 38 Cl-for-Cl substitution yields are close to statistical. The distribution for thermal exchange reactions is however, selective. The 3, Cl-for-H substitution yield is less than 1 % per Η atom-aromatic and methylic-and is scavenger independent. The 3, Cl-for-CH 3 substitution yield is also about 1 %, whereas in a 1 :1 :1 mixture the o : m ; ρ ratio is not far from statistical.

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The reactions of recoil " C1 atoms (produced in a high flux nuclear reactor) with liquid chlorobenzenes were investigated. The yields of " CI-for-H and Q-replacement reactions, of inorganic Compounds and of polymers were measured in the presence of scavengers, by GLCtechniques and by gelfiltration over Sephadex. In unscavenged chlorobenzene, C^ Hj" C1 (52%) is formed via a direct hot replacement reaction (5%), via a thermal exchange reaction (28%) and via a radiation induced exchange reaction (19%). It is believed that hot H-abstraction leads to the inorganic yield, because this yield is not influenced by the addition of organic unsaturated Compounds. The total organic yield is not in-fluenced by the addition of organic scavengers, but the natura of the products depends considerably on the kind of scavenger used.Ophthalmie Research Institute (lOI)