scholarly journals Fast ring-opening of an intermediary α-stannyl-β-cyclopropylvinyl radical does not support formation of an α-stannylvinyl cation in the O-directed free radical hydrostannation of dialkyl acetylenes

2019 ◽  
Vol 55 (96) ◽  
pp. 14454-14457 ◽  
Author(s):  
Hamish A. Watson ◽  
Soraya Manaviazar ◽  
Hannah G. Steeds ◽  
Karl J. Hale
Keyword(s):  
Free Radical ◽  
Ring Opening ◽  
Propargyl Alcohol

O-directed hydrostannation of β-cyclopropyl propargyl alcohol 22 with stannanes and cat. Et3B in THF/H2O or PhMe/MeOH fails to deliver any detectable products of α-stannylvinyl cation capture.

Free-radical ring-opening polymerization of 2-(o-chlorophenyl)-4-methylene-1,3-dioxolane

1993 ◽  
Vol 30 (1) ◽  
pp. 7-12 ◽  
Author(s):  
Simona Morariu ◽  
Emil C. Buruiana ◽  
Bogdan C. Simionescu
Keyword(s):  
Free Radical ◽  
Ring Opening ◽  
Ring Opening Polymerization ◽  
Radical Ring

Free-Radical Ring-Opening Polymerization of Cyclic Allylic Sulfides

1996 ◽  
Vol 29 (22) ◽  
pp. 6983-6989 ◽  
Author(s):  
Richard A. Evans ◽  
Ezio Rizzardo
Keyword(s):  
Free Radical ◽  
Ring Opening ◽  
Ring Opening Polymerization ◽  
Radical Ring

General procedures in chain-growth polymerization

2004 ◽  
Author(s):  
Najib Aragrag ◽  
Dario C. Castiglione
Keyword(s):  
Free Radical ◽  
Ring Opening ◽  
Point Of View ◽  
Polymerization Process ◽  
Undergraduate Teaching ◽  
Chain Growth ◽  
Reaction Conditions ◽  
Growth Processes ◽  
Reagent Purity ◽  
Step Growth

This chapter is intended to provide a general introduction to the laboratory techniques used in polymer synthesis, by focusing on some relatively well-known polymerizations that occur by chain-growth processes. In this way some of the more commonly used procedures in polymer chemistry are described. Due to the nature of the intermediates produced, such as free radicals, carbanions, carbocations, together with a range of organometallic species, the techniques often involve handling compounds in the complete absence of oxygen and moisture. Because of this the best results may require quite sophisticated equipment and glassware; however, it is our intention to show that the general procedures are accessible to any reasonably equipped laboratory, and indeed some of the techniques are suitable for use in an undergraduate teaching laboratory. Chain-growth polymerization involves the sequential step-wise addition of monomer to a growing chain. Usually, the monomer is unsaturated, almost always a derivative of ethene, and most commonly vinylic, that is, a monosubstituted ethane, 1 particularly where the growing chain is a free radical. For such monomers, the polymerization process is classified by the way in which polymerization is initiated and thus the nature of the propagating chain, namely anionic, cationic, or free radical; polymerization by coordination catalyst is generally considered separately as the nature of the growing chain-end may be less clear and coordination may bring about a substantial level of control not possible with other methods. Ring-opening polymerizations exhibit many of the features of chain-growth polymerization, but may also show some of the features expected from stepgrowth polymerizations. However, it is probably fair to say that from a practical point of view the techniques involved are rather similar or the same as those used in chain-growth processes and consequently some examples of ring-opening processes are provided here. It is particularly instructive to consider the requirements of chain-growth compared to step-growth processes in terms of the demands for reagent purity and reaction conditions.

Free Radical Reactions on Soluble Supports from Ring-Opening Metathesis

2001 ◽  
Vol 3 (21) ◽  
pp. 3397-3399 ◽  
Author(s):  
Eric J. Enholm ◽  
Maria E. Gallagher
Keyword(s):  
Free Radical ◽  
Ring Opening ◽  
Radical Reactions ◽  
Free Radical Reactions

Free-Radical Polymerization and Ring-Expansion of a Cubane Acrylate: a Unique Low-Shrink Polymer

2009 ◽  
Vol 62 (2) ◽  
pp. 145 ◽  
Author(s):  
Alison E. McGonagle ◽  
G. Paul Savage
Keyword(s):  
Free Radical ◽  
Radical Polymerization ◽  
Ring Opening ◽  
Free Radical Polymerization ◽  
Ring Expansion ◽  
Side Chain ◽  
Molecular Volume ◽  
Acrylate Polymer

A pendant cubane substituent has been incorporated into an acrylate polymer side chain to give poly[methyl 4-(acryloyloxymethyl)cubane carboxylate]. Treating this polymer with a rhodium(i) salt triggers a catalytic, ring-opening rearrangement of the cubane substructure to cyclooctatetraene, with a concomitant expansion in molecular volume. This system offers a unique opportunity to reverse the shrinkage associated with polymerization.

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