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 radical anion and the four substrates trimethylsulfonium iodide, methyl iodide, methyl bromide and methyl chloride in N,N-dimethylformamide has been investigated. By comparing the product distribution for the different methyl systems it is shown that a competition between an electron transfer and an S(N)2 mechanism exists. Normally aromatic radical anions 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 model is used to give a qualitative interpretation of the experimental results.