Improved sustainable ionic liquid catalyzed production of symmetrical and non‐symmetrical biological wax monoesters

Abstract

Biological wax esters are important commercial products used in various industrial and medicinal fields. These valuable compounds can be synthesized via several chemical and enzymatic reactions which have some advantages and more disadvantages. In particular, many strong acid catalysts cause undesirable structural changes in unsaturated fatty acids molecules. In the present study easily accessible 1‐hexadecyl‐3‐sulfoimidazolium chloride as ionic liquid was screened as a mild Brønsted acid metal free catalyst for the chemical esterification or transesterification of equimolar amounts of long chain fatty acids or fatty acid methyl esters respectively with fatty alcohols in solventless medium. The various parameters affecting the yield of the wax ester were optimized, catalyst reuse studies and large scale synthesis were also carried out. According to this alternative practical and green process, a series of wax esters (17 examples) were produced readily in good to excellent yields. There was no undesirable geometric cis‐trans isomerization in unsaturated fatty acids under the reaction conditions used. The catalyst is also quite effective when triglycerides are converted directly to the wax esters via transesterification reaction. In the present study, we present effective and green methods for the preparation and characterization a series of wax esters.

Practical applications: With effortlessly and environmentally friendly method developed in this study, various wax esters can be synthesized as valuable industrial materials. In order to synthesis these esters, there is no any restriction for starting compounds. The most important aspect of the developed procedures is that metallic or strong aggressive acidic catalysts are not used compared to existing procedures. It is possible to carry out large‐scale syntheses of esters with high yields.

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