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The sodium salts of amino acids with hydrophobic fluorenyl methyloxy carbonyl (FMOC) group and short alkyl side chains are found to have surfactant properties. This was ascertained first through visual observation of concentration dependent solution behavior and then confirmed by tensiometry measurements. The critical micelle concentrations (CMCs) for the sodium salts of FMOC-l-valine, FMOC-L-leucine, and FMOC-L-isoleucine have been determined to be ~0.1 M. The sodium salt of FMOC-l-norleucine forms a gel at >0.2 M. Powder X-ray diffraction measurements indicated that these surfactants adopt bilayer structures. Three different chiroptical spectroscopic properties, namely optical rotation, electronic circular dichroism, and vibrational circular dichroism, are presented for these surfactants. The specific rotation is found to exhibit an unprecedented increase with concentration beyond CMC. This observation opens up a new area of research relating the concentration dependent increase in specific rotation to the size and shape of aggregates formed by the surfactants.

In this study, the conformation of the amphiphilic lauryl esters of L-tyrosine (LET) and L-phenylalanine (LEP) in water and dimethyl sulfoxide is established. The alkyl chain protons of LEP in D(2)O appear at δ 1.010-1.398 and show an upfield shift and large line width, suggesting the proximity of the phenyl ring to the alkyl chain in contrast to that of LET. Quite interestingly, in DMSO-d(6), the (1)H NMR spectra of LET and LEP show a strong similarity that is suggestive of an orientation that positions the aromatic ring and aliphatic chain away from each other. These results are substantiated with two-dimensional nuclear Overhauser enhancement spectroscopy (2D NOSEY). Theoretical molecular models of the conformation at the interface corroborate the experimental findings. Investigations of the solvent polarity and chemical structure-dependent conformation are discussed.

Three different chiroptical spectroscopic methods, namely, optical rotation, electronic circular dichroism (ECD), and vibrational circular dichroism (VCD) have been evaluated for studying the aggregation of sodium dodecylsulfate (SDS), an achiral surfactant, using garcinia acid disodium salt (GADNa) as a chiral probe. The specific rotation and ECD of GADNa are found to be altered by the aggregation of SDS, suggesting for the first time that achiral surfactants can be characterized with chiroptical spectroscopy using appropriate chiral probes. In addition, a chiral compound, fluorenyl methyloxy carbonyl l-leucine sodium salt (FLNa) is found for the first time to behave as a surfactant in water, with 205 Å(2) surface area per molecule at the air-water interface, critical micelle concentration (CMC) of 0.18 M, and Gibbs energy of micellization of -14 kJ/mol. The specific rotation of FLNa in water is found to increase with concentration beyond CMC, suggesting the formation of chiral aggregates. Different conformations of FLNa amenable to micellization have been identified using quantum chemical conformational analysis and their specific rotations calculated. The formation of lamellar aggregates of FLNa in water is suggested to be the cause for increase in specific rotation with concentration beyond CMC.