Association of fatty acids in the liquid phase

Using high paraffins as solvent the association of the fatty acids has been investigated in the liquid phase by an infra‐red spectrophotometric method. Firstly, the association of stearic acid was investigated at temperatures between 40° and 220° C and at concentrations from 0.02 mole/kg up to the pure acid. The degree of association and the equilibrium constants were calculated from the relative intensities. From the temperature dependence of the equilibrium constant a heat of dissociation of 13,400 cal/mole and a standard entropy change of 24 cal/mole × degree could be calculated. Measurements with other fatty acids showed that neither the chain length nor the presence of one or two double bonds, nor the branching of the chain influences the association. The relatively high heat of dissociation and entropy indicate that the high paraffins are very indifferent solvents for the polar parts of the molecular; little or no solvation of these parts occurs.