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Step-growth polymerization in which terminal diene groups undergo intermolecular olefin metathesis. Removing a volatile alkene coproduct can drive conversion.

A carbon fragment doubly bonded to a metal in the present organometallic usage. Metal–alkylidene exchange with an alkene underlies olefin metathesis.

A four-membered ring containing one metal and three carbon atoms. Its formation and alternate fragmentation exchange alkylidene groups during olefin metathesis.

The two terminal alkenes undergo olefin metathesis. Their terminal methylene groups combine to give U = ethene, $\mathrm{C}{\mathrm{H}}_2=\mathrm{C}{\mathrm{H}}_2$. Connecting the two internal alkene carbons of the same molecule gives Z, the unsaturated crown ether macrocycle. Following the drawn chain gives four oxygens, six carbons in the three internal ethylene links, two O-adjacent methylenes at the ends and two alkene carbons: a 14-membered ring containing four oxygens.

The ring connectivity is specified completely by the cyclic sequenceThe final methylene reconnects to the first alkene carbon. The examination does not fix alkene stereochemistry, so a single E/Z assignment is not required.

At high concentration, intermolecular encounters compete strongly with ring closure, giving Y, an unsaturated polyether formed by acyclic diene metathesis polymerization. Its repeat connectivity can be writtenFor a finite linear chain, terminal groups depend on conversion and work-up; its internal repeat is the relevant structural answer. Reduced pressure removes ethene and promotes metathesis conversion, while dilution reduces bimolecular chain growth relative to intramolecular closure. These competing routes are documented by the original authors' chemical study.^[ref]

Intramolecular olefin metathesis connecting two alkene sites into a ring. Terminal-alkene substrates can release ethene; concentration and preorganization influence competition with chain growth.

Chain growth by successive olefin metathesis steps that open cyclic alkenes. Relief of ring strain can offset the loss of monomer translational entropy.