Relative Reactivities of Nucleophiles Derived from Group 6A toward Aryl Radicals

Article abstract of DOI:10.1021/jo00177a020

Competition experiments have been carried out in liquid ammonia at reflux temperature to determine the relative rate constants for the coupling reactions of nucleophiles derived from group 6A of the periodic table toward aryl radicals.The nucleophiles studied were of type PhZ- (Z=S, Se, Te).It has been proposed that these nucleophiles react under photochemical stimulation with haloaromatic substrates through the S_RN1 mechanism of aromatic substitution.The experimental results suggest that the coupling reaction aryl radical-PhZ- anion can be reversible or irreversible depending on the nature of the aryl moiety and the PhZ- nucleophile.Relative rate constants have been determined under conditions of irreversible coupling of the nucleophiles PhZ- (Z=S, Se, Te) with 2-quinolyl radicals.Results here reported indicate an increasing reactivity as we go down the group: PhO- (0.0), PhS- (1.00), PhSe- (5.8), PhTe- (28).The relative rate constant when one of the coupling reactions is reversible supports our mechanistic suggestions.