Specific optical rotation is a versatile tool for the identification of critical micelle concentration and micellar growth of tartaric acid–based diastereomeric amphiphiles

Abstract

Four novel tartaric acid-based diastereomeric chiral amphiphiles, two being enantiomers of the other two, have been synthesized and investigated using chiroptical spectroscopic methods, along with tensiometry and dynamic light scattering experiments. We found that an inflection point in specific optical rotation (SOR) values at ~0.32 mM corresponds to the critical micelle concentration (CMC). The increase in magnitude of SOR values beyond CMC corresponds to the growth of aggregates. For enantiomers, oppositely signed SOR values were observed, ruling out the possibility for the presence of aggregation size mediated artefacts. SOR values did not exhibit concentration dependence for a chiral tartaric acid based non-aggregating analogue further establishing the absence of artefacts or anomalous interaction of tartaric acid based head group with solvent. Electronic circular dichroism spectra showed no significant changes in band positions or intensities with concentration. Due to the requirement for higher concentrations (~200 mM) needed to obtain vibrational circular dichroism spectra, these measurements are not found to be useful for studying concentration dependent properties of chiral amphiphiles.

Amphiphilic Low-Molecular-Weight Gelators Bearing β-S-N-Acetylglucosamine Linked to a Tartaric Acid Scaffold: Synthesis, Self-Assembly and Wheat Germ Agglutinin Binding

“…Considering the excellent results previously obtained with the tartaric acid scaffold to promote chiral self-assembly [29,33], we synthesized β-S-(N-acetyl)glucosamine derivatives to obtain amphiphiles that would be recognized by WGA and could also potentially self-assemble to produce supramolecular gels. In order to modulate the solubility (and self-assembly) in water and other organic solvents, the two amphiphiles differed in the length of the alkyl chain of the fatty acids, i.e., octanoic acid (caprylic acid, amphiphile 1) and dodecanoic acid (lauric acid, amphiphile 2).…”

Computational methods and points for attention in absolute configuration determination

“…Some typical chiral molecules were used in the study (Egidi et al, 2019). As one of the simplest and cheapest tools in AC determination, calculating chiral molecular OR and then comparing it with the experimental value is a valid and effective method for OR values that are generally not less than 20 degrees (Raghavan and Polavarapu, 2017). OR and ORD have been widely used in the study of AC (Reinscheid and Reinscheid, 2016;Saito and Schreiner, 2020).…”

Determining the water solubility of difficult-to-test substances: A tutorial review

“…Several other methods have been developed for CMC determinations. Non-invasive physical methods include capillary electrophoresis [81][82][83], speed of sound measurements [84,85], resonance Rayleigh scattering [86], static and dynamic light scattering [74,87,88], potentiometry [89], nuclear magnetic resonance, NMR [90,91], diffusion ordered spectroscopy NMR [92,93], ultrasonic spectroscopy [94], fiber-optical measurements [95], induction current [96], chemiluminescence [97] and chiroptical spectroscopic methods [98].…”