Synthesis and Investigation of Surface Tension Properties of Fatty Pyrimidinium Betaines

A novel series of fatty betaines containing a pyrimidine ring with different alky chain lengths were synthesized by condensation of fatty N,N'-diphenylalkylamidines with a specific highly reactive malonic ester derivative under mild conditions. The chemical structures of products were characterized by common spectroscopic analyses (FTIR, mass spectra, 1H NMR, and 13C NMR spectrometry). Equilibrium surface tension and conductivity as a function of concentration of dodecyl pyrimidinum betaine (betaine with a 12 -carbon alkyl chain) in ethanolic solutions were measured and the critical micelle concentration (CMC) was determined at 30 °C. The results showed that the critical micelle concentration (CMC) of dodecyl pyrimidinum betaine is 0.925 mmol/L and the corresponding surface tension (γCMC) is 25.38 mN/m respectively. These results revealed that the synthesized fatty pyrimidinium betaines are efficient amphoteric surfactants making them promising candidates for applications in a very large number of areas.