| Abstract: | The polymerization in bulk of racemic tert-butyl thiirane with a chiral initiator resulting from the reaction between diethylzinc and (? )3,3-dimethyl-1,2-butanediol produces an optically active polymer by preferential consumption of R enantiomer. The unreacted monomer is enriched in S enantiomer. The relative rate r of consumption of R enantiomer versus S enantiomer is as high as 2.8. Obtained polymer could be separated into two crystalline fractions: an optically active fraction, formed from regular sequences of R type enantiomeric units, and an optically inactive fraction which corresponds to a racemate. Experimental results are consistent with a stereospecific mechanism of addition, the two enantiomers being chosen by two different type of sites. The stereoelective process is due to an unequal number of these two types of sites. |
