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Catalytic effect of supramolecular system based on cationic surfactant and monopodands in nucleophilic substitution of phosphorus esters
Authors:Valeeva  F G  Zakharov  A V  Voronin  M A  Zakharova  L Ya  Kudryavtseva  L A  Isaikina  O G  Kalinin  A A  Mamedov  V A
Institution:(1) A. E. Arbuzov Institute of Organic and Physical Chemistry, Kazan Research Center of the Russian Academy of Sciences, 8 ul. Akad. Arbuzova, 420088 Kazan, Russian Federation
Abstract:The data are presented on the synthesis of podands with terminal quinoxaline fragments of rings and their influence on both the micellization properties of cetyltrimethylammonium bromide in a water—DMF solution and kinetics of basic hydrolysis of O-p-nitrophenyl O-ethyl chloromethylphosphonate and O-p-nitrophenyl O-hexyl chloromethylphosphonate in the absence and presence of surfactants. The mechanism of the podand effect on the reaction rate depends on the structures of phosphonate and podand. 1,8-Bis(3-ethyl-1,2-dihydro-2-oxoquinoxalin-1-yl)-3,6-dioxaoctane inhibits the basic hydrolysis of the substrates to 3—4 times. In a micellar solution of the surfactant, an approximately 20-fold acceleration of the reaction rate constant is observed. The observed rate constant decreases when podand is added to a micellar solution. The catalytic effect of the polycomponent system is due to concentrating of the reactants. The micellar microenvironment can exert both positive and negative effects on the reactivity of phosphonates.
Keywords:podands  phosphorus acid esters  kinetics  hydrolysis  cetyltrimethylammonium bromide  micelles
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