Micellization-induced conformational change of a chiral proline surfactant.
A proline surfactant including two chiral carbons, sodium N-dodecanoyl-(4R)-hydroxy-L-prolinate (SDHP), has been synthesized, and its micellization behavior in aqueous solution has been investigated by 1H NMR spectroscopy. Two conformational isomers of SDHP, namely, Z and E, are discriminated in the NMR time scale, and critical micelle concentration is derived for each isomer separately. The transformation from E to Z is observed upon micellization, and the amount of Z isomer is approximately three times that of E isomer in the equilibrated system. Moreover, the variation in chemical shifts with the surfactant concentration reveals the shielding effect of the carboxyl group on the syn-side protons of the pyrrolidine ring, which implies that the pyrrolidine rings arrange in a side-to-side manner and lie parallel to the plane of the carboxyl bonds in the neighboring molecules. The difference in the directions of the carbonyl group between Z and E isomers essentially determines their different micellization abilities and molecular arrangements in the micellization process.
Deng
Manli
M
Beijing National Laboratory for Molecular Sciences, Key Laboratory of Colloid and Interface Science, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, People's Republic of China.
Huang
Xu
X
Wu
Rongliang
R
Wang
Yilin
Y
D000465:Algorithms; D006909:Hydroxyproline / Q000737:chemistry; D007850:Lauric Acids / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D008823:Micelles; D008958:Models, Molecular; D008968:Molecular Conformation; D015394:Molecular Structure; D011392:Proline / Q000737:chemistry*; D013237:Stereoisomerism; D013501:Surface-Active Agents / Q000138:chemical synthesis / Q000737:chemistry*
D007850:Lauric Acids; D008823:Micelles; D013501:Surface-Active Agents; C030358:lauric acid; D011392:Proline; D006909:Hydroxyproline