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17 O‐NMR Spectra of Cyclopropenones and Tropone. Oxygen Exchange with Water
Author(s) -
Dahn Hans,
UngTruong MyNgoc
Publication year - 1987
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19870700818
Subject(s) - tropone , chemistry , ketone , acetophenone , nucleophile , nmr spectra database , medicinal chemistry , proton nmr , spectral line , stereochemistry , organic chemistry , catalysis , physics , astronomy
Whereas tropone ( 2 ) and a cyclopropanone 5 show rather normal ketone signals in their 17 O‐NMR spectra, the two cyclopropenones 1a , and lb exhibit exceptionally high shielding, indicating a structure closer to a O − formula than to a ketone. For comparison, an enolate and several phenolates have been measured. In order to test the ketonic character, the nucleophilic addition of water was determined by the rate of isotopic O‐exchange between ketone and water: 2 exchanged ca. 20 times slower than acetophenone, whereas la reacted very much more slowly.