INVESTIGATION OF THE COMPETITION BETWEEN ELECTRON-TRANSFER AND S(N)2 IN THE REACTION BETWEEN ANTHRACENE RADICAL-ANION AND THE METHYL HALIDES

The mechanism of the reaction between electrogenerated anthracene radi cal anion and the four substrates trimethylsulfonium iodide, methyl io dide, methyl bromide and methyl chloride in N,N-dimethylformamide has been investigated. By comparing the product distribution for the diffe rent methyl systems it is shown that a competition between an electron transfer and an S(N)2 mechanism exists. Normally aromatic radical ani ons are considered to be very strong electron donors, but in the cases presented the S(N)2 mechanism actually constitutes 0, 25, 77 and 97%, respectively, of the two reaction paths. The configuration mixing mod el is used to give a qualitative interpretation of the experimental re sults.