Polymer reagents, polymeric

Other reasons for a wide propagation of polymerization in water include (1) reduction of energy consumed to separate the initial monomer in crystal form (acrylamide is produced and used in the aqueous solution form), which, in addition, is associated with the probability of its spontaneous polymerization, and (2) recovery of the organic solvents, which results in less environmental pollution and the elimination of the stage of solution of polymer reagents used, as a rule, in the form of the aqueous solutions. 

Another important application of the polymer reagent method is in the synthesis of cyclic peptides. In this approach, the amino-protected linear peptide (7(5) is converted into the corresponding polymeric active ester (17) by coupling it to a cross-linked hydroxyl function containing polymer (eg. 12) on deprotection of the amino group and subsequent neutralization, the cyclic peptide (18) is obtained in good yields 109 110> ... 

Thus, in this method the stepwise synthesis proceeds on the soluble polymer, as in the liquid phase method the only difference is in the coupling step where the carboxyl component is an insoluble polymeric active ester. The use of the solubilizing C-terminal macromolecular protecting group overcomes the limitations encountered in the original application of the polymer reagent method of peptide synthesis. However, due to the steric limitations characteristic of the polymer-polymer interactions, the attainment of quantitative coupling in each step of the synthesis can be difficult in this method. 

F. J. Waller, Catalysis with a Perfluorinated Ion-Exchange Polymer, in Polymeric Reagents and Catalysts (ed. W. T. Ford), American Chemical Society Symposium Series (ACS), 308, Washington DC, 1986, Chap. 3, p. 42. 

Mixtures of Ni and Co salts with organoaluminum reagents catalyze the polymerization of 1,3-butadiene, whereas these catalysts are not effective for alkene polymerization due to facile chain transfer by /1-hydrogen elimination of the growing polymer. The polymerization of 1,3-butadiene usually proceeds via the intermediate n-allyl complexes, which are more stable than the alkyl metal complexes and hardly cause any /1-hydrogen elimination [56]. The late transition metal compounds polymerize 1,3-butadiene even in... 

I. Chemical tests and reagents—Congresses. 2. Catalysts—Congresses. 3. Polymers and polymerization—Congresses. 

Polymers and polymerization. 2. Chemical tests and reagents. 3. Chemistry, Organic. I. Narang,... 

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