Lipase catalysed conversion of triglycerides to amides in liquid ammonia†. (25th May 2016)

• Record Type: Journal Article
• Authors: Griffin, Joseph M.; Atherton, John H.; Page, Michael I.; Powles, Nicholas T.
• Other Names: Herges Rainer guestEditor.
• Is Part Of: Journal of physical organic chemistry. Volume 29:Number 12(2016)
• Page Start: 768
• Page End: 772
• Publication Date: 2016-05-25
• Subjects: catalysis -- enzymes -- liquid ammonia; Chemistry, Physical organic -- Periodicals; 547.1
• DOI: 10.1002/poc.3583
• Languages: English
• ISSNs: 0894-3230

Abstract

Abstract: Immobilised lipase B ( Candida antarctica lipase B) is, perhaps unexpectedly, catalytically active in liquid ammonia and exhibits chain length selectivity in the ammonolysis of triglycerides. Using glycerol triacetate as the substrate, the ammonolysis of only the first ester linkage is catalysed by the enzyme, whereas for glycerol tributyrate, the cleavage of all three ester groups is catalysed and converted to the corresponding amide. These observations represent the first example of the use of enzymes in pure liquid ammonia, exemplifying bothcatalysis and selectivity. Glycerol trioleate is relatively stable in liquid ammonia but, with Candida antarctica lipase B present, readily undergoes ammonolysis to give oleamide and glycerol even at 25 °C. There is no enzyme‐catalysed ammonolysis with the native lipase as it is insoluble in liquid ammonia. Thesolvolysis of triglycerides in liquid ammonia occurs by a stepwise conversion of the triester to diester to monoester to glycerol with one equivalent of carboxylic acid amide produced at each stage. The pseudo first‐order rate constants for each of the three steps of the uncatalysed ammonolysis of triglycerides in liquid ammonia decrease with increasing alkyl chain length in the carboxyl residue as expected from a small steric effect. Copyright © 2016 John Wiley & Sons, Ltd. Abstract : The image shows the use of enzymes in pure liquid ammonia, exemplifying both catalysis and selectivity.