`Watching' lipase-catalyzed acylations using 1H NMR: competing hydrolysis of vinyl acetate in dry organic solvents |
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| Institution: | 1. Pharmaceutical Chemistry Section, Van Yüzüncü Yil University, Van, Turkey;2. SAFF Chemical Reagent Research Laboratory, VAN-TEKNOKENT, Van, Turkey;1. Department of Chemistry, Bannari Amman Institute of Technology, Sathyamangalam 638 401, India;2. Department of Chemistry, Thiagarajar College of Engineering, Madurai 625 015, India;3. Institute of Chemistry, Academia Sinica, Taipei 115, Taiwan;4. School of Chemistry, Madurai Kamaraj University, Madurai 625 021, India;1. H. No. 749, G. B. S & D. C. Society, SEC. 48A, Chandigarh 160047, India;2. S.O.S. Chemistry, Jiwaji University, Gwalior, India;3. Sc. ‘F’ & HOD TIRC, DRDE, Gwalior, India |
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| Abstract: | Lipase-catalyzed acetylations of 1-phenylethanol with vinyl acetate were monitored in situ by 1H NMR spectroscopy. Surprisingly, even under dry conditions (no added water) the major reaction was hydrolysis of the vinyl acetate, not acetylation of the substrate. Because this competing hydrolysis consumes water and releases acetic acid, the reaction conditions in lipase-catalyzed acylations are not constant, but vary with the reaction time. Addition of a chiral shift reagent reveals the enantiomeric purity of the starting alcohol and allows calculation of the enantiomeric ratio, E, for the reaction. |
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