Gemini Pyridinium Surfactants:  Synthesis and Conductometric Study of a Novel Class of Amphiphiles¹

A new series of pyridinium cationic gemini surfactants was prepared by quaternization of the 2,2'-(alpha,omega-alkanediyl)bispyridines with N-alkylating agents, whose reactivity is briefly discussed. Particularly useful was the use of long-chain alkyl triflates (trifluoromethanesulfonates) for both overcoming the sterical hindrance in the pyridines and obtaining higher synthetic yields. Well-known 4,4'-(alpha,omega-alkanediyl)bis(1-alkylpyridinium) structures showed narrow temperature ranges for practical applications, due to their high Krafft points, while the new 2,2'-(alpha,omega-alkanediyl)bis(1-alkylpyridinium) series, accounted for good surface active properties. Due to the Krafft points below 0 degrees C, they could be exploited as solutions in water at any temperature. The characterization of the behavior of the series was performed by conductivity measurements. Some of the proposed structures exhibited unusual surface active behavior, which was interpreted in terms of particular conformational arrangements.