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1 H and 13 C NMR study of the effects exerted by an oxirane ring in the epoxybicyclo‐[2.2.2]octane series
Author(s) -
Christol H.,
Laffite C.,
Plénat F.,
Renard G.
Publication year - 1981
Publication title -
organic magnetic resonance
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0030-4921
DOI - 10.1002/mrc.1270170207
Subject(s) - chemistry , octane , dihedral angle , ring (chemistry) , bicyclic molecule , epoxide , proton nmr , molecule , stereochemistry , carbon 13 nmr , organic chemistry , hydrogen bond , catalysis
The 1 H and 13 C NMR spectra of 2,3‐disubstituted exo ‐5,6‐ and endo ‐5,6‐bicyclo[2.2.2]octanes, and the corresponding alkanes, have been investigated to determine the effects exerted by an oxirane ring. The 1 H NMR study showed that the anti protons, H‐7 a and H‐8 a , are significantly shielded and the syn protons, H‐7 s and H‐8 s , are deshielded, although to a smaller extent, by the exo ‐oxirane. An endo ‐oxirane has practically no effect on the same protons. The stereochemistry of epoxybicyclo[2.2.2]octanes is, thus, easily deduced from 1 H NMR data. The 13 C NMR study of the epoxy compounds provided an estimate of the value of α, β, γ syn and γ anti effects (to the epoxide oxygen) of an oxirane ring. In these rigid bicyclic molecules, of known geometry, the γ syn and the γ anti effects are of the same value, even though the dihedral angles are very different (0° and 120°).