Complexation in the heptanoic acid-heptylamine system

The complexation between heptylamine and heptanoic acid has been elucidated at 298.15 K using spectroscopic methods and also by measuring macroscopic quantities such as viscosity, conductivity and surface tension. Fourier tra nsform IR and C-13 NMR measurements point towards the existence of a compou nd consisting of one amine molecule and one acid molecule in an equimolecul ar mixing ratio. These suggestions are supported by viscosity and surface t ension measurements. This compound is further able to interact with excess acid, but similar behaviour is not observed with excess amine. The equimole cular compound behaves like a catan-ionic surfactant: this is seen in the p hase diagram for the heptylamine-heptanoic acid-water system at 298.15 K, w here the dominating phase is the lamellar liquid-crystalline phase. This ph ase is in equilibrium with almost pure water. At low water content a soluti on phase extending from the binary heptylamine-heptanoic acid axis and cove ring all mixing ratios between the amine and the acid is also present.