Conformational behavior of aqueous micelles of sodium N-dodecanoyl-L-prolinate

In this paper we report the multinuclear NMR investigation of sodium N-dode canoyl-L-prolinate (1), in CD3OD and in D2O, at various concentrations. Due to the amide bond, this surfactant has two conformational isomers, l-E and 1-Z, and the ratio [1-E]/[1-Z] in micellized surfactant is different from that in CD3OD or in D2O at [1] < cmc (ca. 0.5 and 1.5, respectively). Under micellar aggregation conditions, the presence of the two isomers resulted in two signals for most of the nuclei. Because this feature is not observed under nonaggregating conditions, this indicates that the isomers micellize on the basis of a different stereochemical code in conformational domains that give two different H-1 and C-13 NMR spectra. Na-23 spin relaxation tim e shows that the counterion is highly bonded to the aggregate.