New amphoteric surfactants derived from lysine. I. Preparation and properties of N^ε-acyllysine derivatives-acyllysine derivatives

Abstract

New amphoteric surfactants were prepared from N^ε-acyllysine which was obtained by the thermal dehydration of a higher fatty acid salt of lysine and was not soluble in water. N^α,N^α-dimethyl-N^ε-acyllysine was prepared by the catalytic reductive condensation of N^ε-acyllysine ester with formaldehyde in good yield. N^α,N^α,N^α-trimethyl-N^ε-acyllysine was obtained from the reaction of N^α,N^α-dimethyl-N^ε-acyllysine ester with methyl iodide. Confirmation of the structure of these derivatives was obtained by spectrometric and spectroscopic analyses.

The solubility of N^ε-acyllysine was improved significantly by the introduction of N^α-methyl groups. Physicochemical and surface active properties of the derivatives were investigated in terms of isoelectric points, dissolution temperatures, surface tensions, critical micelle concentrations (cmc), foaming properties and wetting powers. N^α,N^α,N^α-trimethyl-N^ε-acyllysine had lower dissolution temperatures than N^α,N^α-dimethyl-N^ε-acyllysine. The latter showed lower surface tensions than the former at cmc. N^α,N^α-dimethyl-N^ε-lauroyllysine was best in wetting power and foaming property.