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Chemistry International
Vol. 24, No. 6
November 2002

 

Highlights from Pure and Applied Chemistry


Definitions Relating to Stereochemically Asymmetric Polymerizations (IUPAC Recommendations 2001)

by K. Hatada, J. Kahovec, M. Barón, K. Horie, T. Kitayama, P. Kubisa, G. P. Moss, R. F. T. Stepto, and E. S. Wilks
Pure and Applied Chemistry, Vol. 74, No. 6, pp. 915-922 (2002)

Asymmetric polymerization has been of interest to many academic and industrial polymer scientists, but IUPAC has made no explicit reference to the classification and definitions of reactions involving the asymmetric synthesis of polymers. This document presents definitions concerned with asymmetric and related polymerizations, with examples included to clarify the meaning of the definitions.

Asymmetric polymerization is defined as "A polymerization that proceeds in an unsymmetrical manner in terms of chirality under the influence of chiral features present in one or more components of the reaction system." The asymmetric polymerizations embrace two main categories, "asymmetric chirogenic polymerizations" and "asymmetric enantiomer-differentiating polymerizations," which are defined as follows:

Asymmetric chirogenic polymerization: An asymmetric polymerization in which the polymer molecules formed contain one (or more) new type(s) of elements of chirality not existing in the starting monomer(s).

An example of asymmetric chirogenic polymerization: Polymerization of penta-1,3-diene by 1,4-addition with an optically active catalyst gives an optically active polymer comprising configurational repeating units with predominantly one type of chirality center.

 

Asymmetric enantiomer-differentiating polymerization: An asymmetric polymerization in which, starting from a mixture of enantiomeric monomer molecules, only one enantiomer is polymerized.

An example of asymmetric enantiomer-differentiating polymerization: Polymerization of racemic 3-methylpent-1-ene (MP) using an optically active catalyst may give an optically active polymer by a polymerization that is partially asymmetric; preferential consumption of one of the two enantiomers leaves a monomer mixture having optical activity.

 

Some asymmetric chirogenic polymerizations give helical polymer molecules of only one screw sense that usually show optical activity due to the helicity. These polymerizations are termed "asymmetric helix-chirogenic polymerizations."

www.iupac.org/publications/pac/2002/7406/7406x0915.html

 

 

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