The kinetic enhancement of polymer-supported reagents for use in organic synthesis and selective metal ion complexation.

摘要

Polymers can be designed with specific chemical properties for application in organic synthesis and selective metal ion complexation. The chemical properties of the polymer-supported reagent are influenced by the structure of the polymer backbone. The focus of this dissertation is to investigate this relationship in the attempt to optimize the kinetics of the polymer-supported reagent for its specific application.; The influence of the polymer structure on the kinetics of an SN 2 displacement mechanism was evaluated by the Hammett correlation. The initial rate of the reaction between the phenoxide resins and benzyl chloride in ethanol decreased with increasing strength of the electron withdrawing group of the substituted phenoxide. A non-linear Hammett correlation of the kinetic data determined a change in the rate limiting step to occur between sigma --0.17 and 1.27. It is proposed that a change in the rate limiting step from ion-pair dissociation to nucleophilic attack is the result of an increased delocalization of the phenoxide electron density. The influence of the microenvironment on the reaction kinetics paralleled that of the reported influence of solvents on the Williamson ether synthesis.; A series of polymer-supported phosphine resins were synthesized to evaluate the structural influence of the polymer on the Mitsunobu etherification of m-cresol with benzyl alcohol. Reaction rates and product yields were compared with the Mitsunobu esterification of benzoic acid with benzyl alcohol. The influence of the microenvironment on the reaction kinetics agreed with Hughes-Ingold theory of solvents effects.; The selective complexation of metal ions by a polymer-supported reagent is hindered in highly acidic solutions due to a collapse of the micropores. A series of phosphonic acid resins were synthesized with varying levels of crosslinking, and studied for their ability to complex Eu(III). The hydrophobicity of crosslink levels between 12% and 25% DVB was determined to increase the matrix sensitivity to the solution pH and decrease the amount of Eu(III) complexed. Pore collapse of the phosphonic acid resin was prevented by sulfonation of the ion-exchange resin.