ISOTOPIC EXCHANGE INVOLVING THE [8]ANNULENE ANION-RADICAL AND ITS DIMERIZATION TO THE [16]ANNULENE ANION-RADICAL

The addition of D2O to hexamethylphosphoramide solutions of the potass ium salt of the [8] annulene anion radical results in the slow (days) formation of the monodeuteriated anion radical (C8H7D.-). However, sev eral days after a similar addition to the sodium salt solution, no C8H 7D- is present. Instead, the anion radical of [16]annulene is found. T hese observations led to EPR and NMR studies, which have revealed the mechanism of each process. The mechanisms are based upon the facts tha t ion association is necessary for the isotope exchange reaction and t he absence of ion association is required for the dimerization. Soluti ons of deuteriated [8]annulene anion radical, [8]annulene dianion, [16 ]annulene anion radical, and [16]annulene dianion can be readily gener ated from reduced solutions of [8]annulene for EPR, NMR, etc. studies by making use of the isotopic exchange and dimerization mentioned abov e.