A comparison of the conformation of micellar and non-micellar sodium octanoate and octanoic acid using 13C–1H and 1H–1H vicinal spin–spin coupling constants

Abstract

¹ H–¹H and ¹H–¹³C vicinal spin–spin coupling has been studied at 21 °C for micellar and non-micellar aqueous solutions of sodium octanoate, aqueous solutions of sodium butanoate and pentanoate, and CDCl₃ and CD₃OD solutions of octanoic acid. For the octanoyl subjects, there is no detectable variation in the proportion of trans conformer with solvent or degree of association except for the CH₂–CH₂ bond adjacent to the carboxy group which shows an increase in fractional trans content of ca. 0.1 on micellisation. In sodium butanoate, the trans fraction is ca. 0.1 lower than in sodium pentanoate owing to the absence of four-bond steric conflicts.