An infrared-spectroscopic study of reversed micellar solutions of sodium n-octanoate and water in n-decanol

The association process to reversed micelles in the system water/sodium n-octanoate/n-decanol is studied by means of wave number shifts in the fundamental infrared region. It is found that the antisymmetric vibration band (σ3), and the scissors vibration band (σ2) of water, together with the antisymmetric stretching vibration band of the ionised carboxylic groups (σCOO-) are capable of detecting and visualising changes in the micellar association equilibria. The information is primarily qualitative, but some rough quantitative estimations are also made. A comparison between the intensities of the narrow σ3-line corresponding to unassociated water OH-oscillators discernible at high dilutions in decanol, and the broad σ3-band of the associated species reveals that the fraction of unassociated OH-groups in water is low, perhaps only a few percent. © 1982.