CHEMOSPECIFICITY OF THE AGGREGATED LITHIUM ISOPRENYL ACTIVE-CENTERS

The microstructure of isoprene oligomers prepared by the use of organolithium initiation both in homogeneous (hydrocarbon solvents) and heterogeneous conditions was investigated with Bruker AM-500 instrument. In case of homogeneous process the content of 3,4-units in the oligomers may be increased at high initiator concentrations and by the use of nonsolvating media. In contrast to these patterns, the heterogeneously produced oligoisoprenes involve 1,2-units and are substantially enriched in 3,4-structures. The results obtained reveal rather high chemospecificity of lithium isoprenyl active centers incorporated in mixed aggregates.