A NEW MECHANISM FOR THE OXIDATIVE POLYMERIZATION OF 4-HALOPHENOLATES TO POLYPHENYLENE OXIDES

In order to elaborate a unitary theory and to explain many contradictory experimental results, a new and general mechanism for the polymerization of 4-halophenolates to polyphenylene oxides is proposed. In accordance with the proposed mechanism, the aromatic halogen atom in the para position, with very low reactivity, is transformed by ''single electron transfer'' from the phenolate anion to the catalyst [polycondensation activated by a ''single electron transfer'' (SET) mechanism] in an extremely reactive aliphatic halogen atom having an alpha-etheric and allylic structure. The ''key'' intermediate of this nonconventional polymerization reaction is assumed to be an intermediary quinol ether synthesized in situ by S(N)2 a simple aliphatic nucleophilic substitution of the reactive halogen by monomeric phenolate anions. The intermediary quinol ethers creates chain extension of the polyphenylene oxide by rearrangement and redistribution reactions. This elaborate mechanism explains a great many of experimental results (including the anomalies sometimes observed in the polymerization of 4-halophenolates) in a unitary way.