Binary freezing point behavior of some saturated and unsaturated fatty acid methyl esters with methyl heptadecanoate

Abstract

The binary freezing point behavior of methyl heptadecanoate with methyl laurate, methyl myristate, methyl palmitate, methyl stearate, methyl elaidate and methyl petroselaidate have been determined. Both stable and metastable polymorphic forms were observed. Methyl laurate formed a simple eutectic with a region of metastable equilibrium. Methyl myristate formed a simple eutectic of stable equifbrium and a soUd solution of metastable equilibrium. Methyl palmitate exhibited a solid solution of metastable equilibrium terminating in a eutectic and a region of discontinuous stable equilibrium. Methyl stearate formed a solid solution of metastable equilibrium and also continuous stable equilibrium which formed an incongruently melting molecular compound that terminated in a eutectic point. Methyl heptadecanonate with the unsaturated eighteen carbon atom acid methyl esters exhibited only simple eutectic points and a small region of metastable equilibrium. The binary freezing point behavior of the methyl esters in general resemble that of the corresponding ethyl esters. The limited results of mixtures of methyl esters of an odd carbon acid with unsaturated acids indicate an induced stabilizing effect caused by unsaturation in the carbon chain.