Oligomeric rings

A much better agreement between theory and experiment is found in the closely-related field of macrocyclisation equilibria. Investigations of the cyclic populations in ring-chain equilibrates set up in typical polymeric systems such as polyesters, polyethers, polysiloxanes, and polyamides take a major advantage from the relative ease with which the cyclic fraction can be separated from the linear fraction and analysed for the relative abundance of the individual oligomeric rings. This is conveniently done by means of modern analytical techniques such as gas-liquid and gel-permeation chromatography (Semiyen, 1976). 

Peters, J.-M., Walsh, M. J., and Franke, W. W. An abundant and ubiquitous homo-oligomeric ring-shaped ATPase particle related to the putative vesicle fusion proteins Sec 18p and NSF. EMBOJ. 1990, 9, 1757-1767. 

The reaction of organic dithiols with dichlorosulfanes may result in the formation of rings, of oligomeric rings, or of polymers (equations 73-75). 

The authors favour reaction (ii), because they believe that steric hindrance would make the formation of oligomeric rings from a-methylvinyl compounds very difficult. 

Hspl04 is a member of the ClpB/HsplOO family of AAA + proteins (ATPases associated with various cellular activities) that characteristically form hexameric or oligomeric ring complexes involved in the energy dependent remodelling of... 

Now if we allow each chain to undergo a reversible ring closure, the final mixture will consist of a virtually infinite number of oligomeric rings, C and chains, M , in equiHbrium with each other (Scheme 3). 

Isopropoxy-4/f-l,3,2-benzodioxaborin (18) has been synthesized and found to react with a variety of hydroxy compounds to replace the isopropoxy group on boron. Aryl boric acids, RB(OH)2, reportedly condense with diols of the type HO(CH a)nOH to yield oligomeric rings (19) of varying size. The reaction of allenyl borates (20) with hydrogen bromide to yield alkenes and alkynes has been published. ... 

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