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17 O, 13 C and 1 H NMR and IR spectral study of crowded ketones: possible intramolecular C—H···O interactions
Author(s) -
Qin Xurong,
Ishizuka Yasuko,
Lomas John S.,
Tezuka Takahiro,
Nakanishi Hiroshi
Publication year - 2002
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/mrc.1056
Subject(s) - chemistry , intramolecular force , alkyl , carbon 13 nmr , chemical shift , substituent , carbon 13 nmr satellite , proton nmr , nmr spectra database , stereochemistry , crystallography , spectral line , nuclear magnetic resonance spectroscopy , medicinal chemistry , fluorine 19 nmr , organic chemistry , physics , astronomy
Unusual behaviour was observed in the study of the 17 O, 13 C and 1 H NMR and IR spectra of crowded (1‐adamantyl)alkyl ketones. As the size of the alkyl substituent is increased, abnormal upfield chemical shifts in the 13 C NMR and downfield shifts in the 17 O NMR of the carbonyl group, as well as downfield shifts in the 1 H NMR of the adamantyl γ'‐protons, are found. In the IR spectrum, the ν CO stretching frequencies of the ketones with bulky substituents show considerable red shifts. Correlation of the NMR shifts with the number of γ‐carbon atoms of the alkyl substituents and comparison with the IR results indicated that there is an intramolecular through‐space CH···O interaction in crowded ketones. This was supported by the results of ab initio calculations. Copyright © 2002 John Wiley & Sons, Ltd.