MONOMER-ISOMERIZATION OLIGOMERIZATION OF 2-ETHYL-1,3-BUTADIENE BY ACID CATALYSTS

Experimental data demonstrated that the cationic oligomerization of 2-ethyl-1,3-butadiene (2EBD) by a superacid (CF//3SO//3H) and a superacid derivative (CH//3COClO//4) accompanied monomer isomerization to 3-methyl-1,3-pentadiene (3MPD) before propagation to yield oligomers of the isomerized monomer as main products in benzene at 50 degree C. Detection of 3MPD in the reaction mixture and **1H-NMR structural analysis of the produced oligomers confirmed the occurrence of this ″monomer-isomerization oligomerization.″ On the other hand, in the presence of a metal halide catalyst (BF//3OEt//2) 2EBD reacted without isomerization and yielded oligomers that were different from those produced by the foregoing superacid catalysts. Monomer isomerization was suppressed in a polar solvent left bracket (CH//2Cl)//2 right bracket or at lower temperatures. The mechanism of the oligomerization with monomer isomerization was discussed.