Substituent effects in hot replacement by recoil halogens. Pt. III. Bromine replacement by recoil and photolytic chlorine atoms

The substituent effect on aromatic bromine replacement by recoil 38Cl and by photolytic Cl atoms has been studied by means of intermolecular competition experiments. Correlation of the results using the Hammett relation has shown that in the presence of I2 scavenger 38Cl → Br replacement occurs essentially via the same mechanism as described for high energy chlorine replacement by 38Cl, 125I and 211At [1]. In the absence of I2 scavenger, however, the substituent effect shows closer similarity to that observed for the replacement by photolytic - thermal - Cl atoms, indicating that the majority of the recoil atoms originating in 37Cl(n, γ)38Cl nuclear process react with benzene derivatives in the liquid phase after slowing down to the thermal energy region. (orig.)