Rotation about the Carbonyl Carbon-Nitrogen Bond in Micelles of N-(Dodecyloxycarbonyl)sarcosinate

Article abstract of DOI:10.1021/ja00383a006

The sodium salt of the title compound forms micelles readily, exhibiting a critical micelle concentration of 6 * 10^-4 M at 25 deg C.Quasi-elastic light scattering shows that most of the micelles are approximately 6.0 nm in diameter, although indications of larger aggregates (ca.170 nm diameter) were also observed.These diameters do not change beyond experimental error over the temperature range 25-50 deg C.Proton NMR experiments were used to determine the kinetics of rotation about the carbonyl carbon-nitrogen bond of the detergent both in micelles and in the monomer.While ΔG<*> for rotation was found to be independent of aggregation state, ΔH<*> and ΔS<*> for the process are substantially larger in the micelle.Variations in the activation parameters as the identity of the counterion is changed suggest that disruption of ionic interactions as the surface of the micelle is a part of the rotational process.