Monomer polymerizations of the

Finally, in a recent study by Walling and El-Taliawi (216) it was shown that solvolytically generated vinyl cations may be reduced by Fe ions in solution to the corresponding vinyl radical. When 2-buten-2-yl triflate was solvolyzed in concentrated ferrous perchlorate solution in the presence of acrylonitrile monomer, polymerization of the acrylonitrile was observed. No such polymerization occurred under identical conditions in the absence of Fe ions. It seems that the polymerization of acrylonitrile was initiated by the vinyl radicals formed by reduction of the intermediate vinyl cation by Fe as follows (216) ... 

While exo/endo isomerization of the substituted monomers had been found to be comparable to that of the parent monomer, polymerization of the substituted monomers was much faster. Under the conditions indicated above for <20% polymer formation in neat samples of PN or PX, both the phenyl and carbomethoxy monomers show >80% polymer formation. This greatly complicates any attempt to dissect isomerization from polymerization in these neat samples. Nevertheless, we were able to establish that, in the lower temperature (195 C) polymerization, the isomeric mixture undergoing polymerization was the same (for the carbomethoxy system) whether we started from CBN or from CVN (195 , 1 hr 71% VN, 23% VX, 6% BN + BX). A similar result was obtained by comparing the polymerization of < >VN and <)>BN. 

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