Inversion of Configuration and Stereoselectivity

In the large mqority of the cationic polymerizations of heterocycles the propaption step proceeds with complete inversion of conf uration. Ihis vras diown for the first time by Vandenberg in the polymerization of ds- and trans-2,3-butene oxides as 

Price cationically polymerized cis- and trans-didmiteroethylene oxides and analyzed the prepared polymCTs by IR spectra This work has recentty been repeated and the microstructure of the chains was studied by the C-NMR method ( C satellitesj ) 

The polymerization of cis- and trans-monomers leads to the followii chain configurations, depending on retention or inversion of configuration  

When a 70/30 mixture of cis- and trans-monomers is used, a 70/30 mixture of threo- to eiythro-diads is obtained. 

in agreement with the results observed by Price, who obtained polymars with a microstructure depending exclusively on the configuration of the monomers C-NMR studies of polymers reveal that polymerizatfon of ethylene oxide almost entirely proceeds through inversion of configuration at the carbon atom attacked by a monomer molecule 

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