RADICAL-CATION NUCLEOPHILE COMBINATION REACTIONS - DISPLACEMENT OF HALOGEN DURING IPSO ATTACK ON HALOANTHRACENE RADICAL CATIONS

Second-order rate constants for the reactions of radical cations of a number of haloanthracenes with pyridine and 2-substituted pyridines were determined in acetonitrile and dichloromethane using electrochemical techniques. Attack at the ipso positions was observed to be less favorable than attack at positions bearing hydrogen. The halo-substituents were observed to exert opposing electronic and steric effects on the second-order rate constants. The 10-positions of 9-haloanthracene radical cations were observed to be nearly 2 orders of magnitude more susceptible to nucleophilic attack by pyridine than the 9,10-positions of the parent radical cation.