Thallation activation barriers

The linear free enogy relationship obsoved for arene donors relates the activation barrier AG for aromatic substitution directly to the CT transiticxi oiergy Aver of the EDA complex. Since Aver pertains to the energetics of the photoionizadons in equations (27) and (28), the correlation suggests that these arene contact ion pairs ate reasonable approximatims to the transition states for both mercuration and thallation, e.g. Scheme 6. 

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