Glide planes, crystalline polymers

A very special case among optically active dienes is given by chiral allenes. Polymerization of (-)-(R)-2,3-pentadiene by organometallic transition metal derivatives [59] gives an optically active crystalline polymer to which the structure reported in Table XVI has been assigned. In fact that structure is the only linear structure not possessing symmetry planes or mirror glide planes. 

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