Two‐stage synthesis of sorbitan esters, and physical properties of the products

Abstract A series of sorbitan‐fatty acid esters with various fatty acid/sorbitol ratios was prepared using a 2‐stage process. In the first stage, sorbitol was dehydrated to sorbitan at 180 °C (using phosphoric acid as catalyst), and in the second stage, the sorbitan was esterified with the fatty acid at 220 °C (sodium hydroxide as catalyst). The course of the reaction was monitored and the composition of final products was determined by thin‐layer chromatography using a flame‐ionisation detector (TLC‐FID). The properties (surface tension, melting points, viscosity) of prepared sorbitan esters depend on the molecular ratio of fatty acid and sorbitol. The described method is suitable for the preparation of sorbitan esters at industrial scale.