Enzymatic synthesis of amide surfactants from ethanolamine

The condensation of a primary amine with fatty acids has been studied to de termine optimum conditions for selective formation of amide surfactants via enzymatic amidification. Monoacylated ethanolamide and the diacylated amid e-ester can be isolated from the reaction mixture, but the monoacylated est er cannot be isolated. The selectivity of the reaction depends on the solub ility of the intermediate amide. Continuous precipitation of this product d ecreases the amount of amide-ester produced. Solubility values of the desir ed product (amide) are reported for different conditions. In acetonitrile, the ethyl ester of the corresponding fatty acid has been u sed successfully to avoid formation/precipitation of the ion-pair of the pr ecursor reagents. In this medium, use of the transacylation reaction permit s one to accelerate the reaction without producing a significant change in the selectivity toward the intermediate amide. This strategy is not success ful in n-hexane where the solubilities of both ethanolamine and its ion-pai r with lauric acid are similar. Results obtained for high loadings of substrates have been analyzed. In n-h exane and acetonitrile, the kinetics of the direct acylation reactions are controlled by the limited solubility of the ion pair formed by the two prec ursor reagents For the transacylation reaction in acetonitrile, at a sustra te loading of 2 mol l(-1) selective production of as much as 92 mole percen t N-acyl ethanolamine was observed in only 1.5 h. (C) 2001 Elsevier Science Inc. All rights reserved.