Esterification of fatty acids at room temperature by chloroform-methanolic HCl-cupric acetate

A new procedure for the preparation of methyl esters from free fatty acids under mild conditions was investigated. Free fatty acids are dissolved in a mixture of chloroform-methanolic HCl-cupric acetate and kept at room temperature for 30 min for complete esterification. The method is suitable for esterification of long-chain acids, such as 18:0, and for very long chain acids, such as 24:0. Fatty acids from brain glycerophosphatides, which included a high concentration of polyenes such as 20:4 (n - 6), 22:4 (n - 6), and 22:6 (n - 3), were also esterified by the same procedure, and neither artifact formation nor loss of unsaturated acids was observed.