Solvent‐free enzymatic synthesis of fatty alkanolamides

Abstract

An environmentally benign and volume efficient process for enzymatic production of alkanolamides is described. Immobilized Candida antarctica lipase B, Novozym435, was used to catalyze the condensation of lauric acid with monoethanolamine. The reaction temperature of 90 degrees C was required to keep the reactants in a liquid state. Stepwise addition of the amine minimized problems caused by the formation of a highly viscous amine/fatty acid ion-pair. The enzyme was both very active and stable under the reaction conditions, with about half of the activity remaining after 2 weeks. The maximum amide yield obtained when using equimolar amounts of the reactants was 75%, which could be increased to 95% upon water removal. Special precautions to avoid co-distillation of the amine were required. Two different strategies to avoid the amine loss are presented.

Catalytic amide formation from non-activated carboxylic acids and amines

“…39 By running the reaction at 90 ºC and adding the ethanolamine in portions to keep it protonated at all times, water could be distilled off under vacuum to afford the surfactant amide in 95% yield. Surfactant ethanolamides were also synthesised by Plastina et al 40 Novozym® 435 was used as catalyst to afford six 50 different ethanolamides from fatty acids in yields ranging from 80-88%.…”

Synthesis of Linoleoyl Ethanolamide

“…Using native oils as acyl donor to synthesize fatty acid ethanolamide aims to obtain nonionic surfactants 19 , while vinyl linoleate is commercially unavailable thesis of fatty acid ethanolamides are more popular compared to other acyl donors. It has been reported that Novozym 435 lipase is an effective biocatalyst for the amidation reaction between free fatty acids and ethanolamine 14,20 and usually results in a better product s quality in color, yield and odor compared to other methods 21 . In addition, sodium methoxide can also be applied to catalyze the amidation reaction at low or high temperature 15,17 , while the amidation reaction conducted in absence of catalysts needs a higher temperature 2 and usually causes various problems in color and odor even though the addition of deodorizers and antioxidants to the process has been suggested to improve product s quality 21 .…”

“…It has been reported that Novozym 435 lipase is an effective biocatalyst for the amidation reaction between free fatty acids and ethanolamine 14,20 and usually results in a better product s quality in color, yield and odor compared to other methods 21 . In addition, sodium methoxide can also be applied to catalyze the amidation reaction at low or high temperature 15,17 , while the amidation reaction conducted in absence of catalysts needs a higher temperature 2 and usually causes various problems in color and odor even though the addition of deodorizers and antioxidants to the process has been suggested to improve product s quality 21 . The main disadvantage using free fatty acid as acyl donor to synthesize fatty acid ethanolamide is the formation of salt ion-pair from equivalent moles of ethanolamine and free fatty acid 21 .…”

“…In addition, sodium methoxide can also be applied to catalyze the amidation reaction at low or high temperature 15,17 , while the amidation reaction conducted in absence of catalysts needs a higher temperature 2 and usually causes various problems in color and odor even though the addition of deodorizers and antioxidants to the process has been suggested to improve product s quality 21 . The main disadvantage using free fatty acid as acyl donor to synthesize fatty acid ethanolamide is the formation of salt ion-pair from equivalent moles of ethanolamine and free fatty acid 21 . The salt is organic solvent insoluble, which may make the amidation reaction less effective in solvent system compared to solvent-free system 14 .…”

“…The salt is organic solvent insoluble, which may make the amidation reaction less effective in solvent system compared to solvent-free system 14 . However, synthesis of saturated fatty acid ethanolamides with more than 12 carbon fatty acid chain is not feasible in solvent-free system with lipase as catalyst since fatty acid ethanolamides have much high melting point, suggesting a high reaction temperature, which will result in the inactivation of enzyme 21 . Thus, based on these considerations, fatty acid methyl esters may be the better acyl donors to synthesize fatty acid ethanolamides compared to free fatty acids.…”