Glycine surfactants derived from dodecenyl succinic anhydride

We report the synthesis and properties of two surfactants with a novel head group based on glycine. A monocarboxylic surfactant N-glycine methyl ester (2-dodecen-1-yl succinamic acid) (I) was prepared by ring opening of an n-alkyl succinic anhydride. Hydrolysis of the ester functionality yields a dicarboxylic acid II. The sodium salts of I and II were effective surfactants at neutral pH giving a low minimum surface tension (\30 mN m-1 at 20°C). At high pH (*12) the surface activity of both surfactants is reduced compared to neutral pH, indicating that at neutral pH an ‘acid soap’ is formed. The pKa of the acid form of the surfactants was determined. Addition of calcium ions reduced the CMC of II but did not reduce the surface tension above the CMC. The resistance of II to calcium ion precipitation was measured at pH 7.