Radical-anion intermediates. Part VI. The effect of a crown ether on the 4H-cyclopenta[def]phenanthrene system

Abstract

The effect of the addition of dibenzo-18-crown-6-ether on the decay of the 4H-cyclopenta[def]phenanthrene radical anion has been examined. In contrast to the second-order kinetics observed in the absence of a crown ether, the decay of radical anion is first order for each of the counterions studied when the crown ether is present in an approximately equimolar quantity. The radical anion is also considerably more stable in the presence of the crown ether, particularly when either K⁺ or Na⁺ is the counterion. The crown ether also markedly influences the position of the contact–solvent separated ion pair equilibrium for the 4H-cyclopenta[def]phenanthryl anion, the selectivity being in the sequence Na⁺ > K⁺ > Li⁺.