2,4.

In the reported program, spiro left bracket 2,4 right bracket hepta-4. 6-diene, a derivative of cyclopentadiene, was polymerized at minus 76 degree C with various triphenylmethyl salts as initiator. The polymer consists only of the 1,2- and 1,4-addition structures, and their contents can be determined by the relative area of the olefin proton peaks. The polymer structure changed characteristically with the polymerization conditions. The content of 1,4-structure decreased with increasing polarity of the medium from 45-70 in toluene to 25-30% in 7:3 CH//2Cl//2-CH//3CN. In 1:1 CH//2Cl//2-toluene, the 1,4-structure content decreased tom 70% to 40% with increasing radii of counteranions. These results were interpreted according to the model of the cationic propagation proposed earlier, as arising from the different tightness of the propagating ion pair.