SyCiTEK – Synthesis of Citric Acid Ester

Scientists at the University of Wuppertal developed a catalytic process for the direct esterification of citric acid. The primary carboxylic acid groups in positions 1 and 3 are esterified with alcohols. The symmetric diester and the asymmetric monoester were selectively obtained. The presented method SyCiTEK is particularly suitable for esterification of citric acid with fatty alcohols, polyethoxylated fatty alcohols, diols and monoglycerides

Application Citric acid esters are already common in the food and cosmetics industries, as well as in cleaning products as emulsifiers or surfactants. Esters are used with mono and diglycerides or polyethoxylated fatty alcohols. The conventional synthesis requires high reaction temperatures and delivers complex non-selective mixtures. Selective ester syntheses are known, but due to the need for protecting groups they are inconvenient and uneconomical. SyCiTEK allows easy and selective access to asymmetric citric acid mono ester and symmetric citric acid diester. These can each be prepared and isolated as main products, or can be directly used as mixtures. The procedure corresponds to the classical esterification. Due to the catalyst, the reaction temperature can be lowered to room temperature instead of the usual 140-160 °C. The primary carboxylic acid functions are esterified selectively. It is noteworthy that fatty alcohols, particularly long chain, such as palmityl and oleyl alcohol can be used. The result is a high-quality surfactant (monoester) or an emulsifier (mono-and diesters).

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