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Chemical transformations on a weakly acidic catalyst studied by 15 N NMR: butanone oxime on silicalite‐1
Author(s) -
O’Neil Parker Wallace
Publication year - 1999
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/(sici)1097-458x(199906)37:6<433::aid-mrc465>3.0.co;2-1
Subject(s) - chemistry , oxime , molecular sieve , chemical shift , catalysis , beckmann rearrangement , amide , hydrolysis , heteronuclear single quantum coherence spectroscopy , nitrile , carbon 13 nmr , nuclear magnetic resonance spectroscopy , organic chemistry
The chemical species formed upon adsorption and subsequent heat treatment of 2‐butanone [ 15 N]oxime ( 1 ) on the dried molecular sieve silicalite‐1 were examined by 15 N NMR spectroscopy. The weak acidity of silicalite‐1, which provided weakly adsorbed organic species, facilitated detection without solid‐state methods. Based on chemical shifts, the predominant species at 25 °C was a physisorbed oxime (−48 ppm). An H‐bonded oxime (−71 ppm) form was detected at −25 °C. A sealed sample of 1 was heated off‐line to attempt catalytic conversion to an amide (Beckmann rearrangement). At 200 °C, 1 was hydrolyzed to an amine (−364 ppm). Higher temperatures (400–500 °C) caused fragmentation of 1 to a nitrile (−135 ppm). No amides were detected. The large chemical shift range of 15 N provides a powerful means for investigating chemical reactions in heterogeneous systems. Copyright © 1999 John Wiley & Sons, Ltd.