Reactions in Micelles, Monolayers, and Liquid Crystals

1991 
Measurement of product ratios from dediazoniation reactions in acidic aqueous solutions of cationic micelles provides a new method for determining the relative interfacial quantities of weak nucleophiles at the surface of association colloids. We determined product yields by HPLC from decomposition of hydrophobic derivatives of benzenediazonium salts in aqueous solutions of cetyltrimethyl-ammonium halide, CTAX (X =C1− and Br−) micelles and 0.1 M HX with added NaX at 40°C. Estimates of the ion exchange constant, Kcl Br≃3, obtained from product ratios in the presence of mixtures of the two ions are independent of added salt, but decrease to about 2 at high Br- mole ratio. Preliminary results in CTABr micelles show that the method can be used with microemulsions and that added BuOH reduces the quantity of interfacial Br− as expected, but surprisingly not interfacial water. Generous financial support was provided by NIH, NSF-U.S. Brazil Cooperative Program, PRF, Research Corporation and The Research Council and BRSG Fund of Rutgers University.
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