These model system studies with pyrene can be translated to the real polymerization systems and explain the anomalous results obtained in some of the block copolymer syntheses. Addition of 1-vinylpyrene monomer to a solution of living polybutadiene, ~vB-, results in normal block copolymer formation. Apparently, the diene anion reacts more rapidly by addition to the vinyl function (eq 5) than with the pyrene nucleus (eq 6). Once all the diene anions have been convertedto BVtt-, the polymerization of the 1-vinylpyrene segment proceeds in a normal manner.~vB~+ CH2=CH ->--CH. CH-In the reverse addition sequence, i.e., addition of butadiene monomer to ^V^-, it appears that the expected crossover reaction occurs and the polybutadiene anion is formed. However, this anion can either continue to polymerize any available butadiene monomer or react with the high local concentration of pyrene rings in the polyvinylpyrene segment of the copolymer. The reaction sequence is illustrated in eq 7-9, where (7r)" refers to a pyrene ring on the PVt segment of the copolymer chain.-Vi-+ CH2=CH-CH=CH2--Vir-B~(7)Reactions 7 and 8 will result in block copolymers of welldefined structure and composition, whereas reactions 9a and 9b will yield ill-defined copolymer materials. The electron-transfer reaction products shown in reaction 9a lead to chain termination and chain coupling, whereas pseudotermination and branching occur as a result of the addition reaction shown in eq 9b. Our model studies with pyrene indicate, however, that block copolymer formation (eq 8) is the preferred reaction mode in nonpolar solvents at moderate or low temperatures.Acknowledgments. The authors gratefully acknowledge Mr. W. J. Stauffer for his fine technical assistance during this study, Dr. D. J. Williams for the esr measurements, and Dr. E. Vanzo for several fruitful discussions.

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gel, eluting the isomerically pure product with 20% acetonehexane: yield 1.833 g (61%); IR (neat) 1670,1645 (C=0) cm™1.The compound should be handled as 12a. Isomerization of Substituted Allylbenzenes (15a-c).Isomerization on 15a-c was effected in boiling toluene by using 2 as a catalyst and a substrate to catalyst ratio of 200.

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