Syntheses and Surface Active Properties of Amphoteric Surfactants from Pyridinemonocarboxylic Acids

N-alkylpyridinium-3-carboxylate (3) and N-alkylpyridinium-4-carboxylate (6), where alkyl groups are n-C8H17, n-C10H21, and n-C12H25, were synthesized and their structures were confirmed by IR and NMR spectra. Krafft point (Kp), critical micelle concentration (cmc), area/molecule at air/water interface, dye solubilizatian, and catalitic activity on the reaction of octyl bromide with saturated aqueous potassium iodide were determined for (3) and (6).The Kp of (3) was much lower than that of (6), and the cmc of (3) was slightly higher than that of (6). The relation between the logarithm of cmc and the number(n) of carbon atons in the alkyl chain of (3) was as follows;log cmc=-0.50n+3.20 by surface tension at 30°C. The slope of log cmc plotted against(n) was nearly equal to that obtained for other amphoteric surfactants such as alkylthiobetaine and N-alkylbetaine. The area/molecule of (3) was quite equal to that of (6), and the solubilizing power of (3) for orange OT was slightly lower than that of (6). The catalitic efficiency of (3) and (6) were fairly good and increased with the increasing alkyl chain length.