W. Wang et al., THE USE OF ANISOTROPIC C-13 CHEMICAL-SHIFTS TO STUDY THE SIDE-CHAIN CONFORMATION OF POLYCRYSTALLINE 2-METHOXYDIBENZOFURAN, Journal of the American Chemical Society, 117(48), 1995, pp. 11984-11988
Using the recently-developed 2D PHORMAT experiment, we have measured a
ccurately and assigned the principal values of the thirteen C-13 chemi
cal shift tensors in 2-methoxydibenzofuran, for which there is no publ
ished diffraction structure. A prediction of the conformation of the m
ethoxy group, obtained by comparing the experimental principal values
with the corresponding shieldings from ab initio calculations, agrees
with a prediction based on the principal values of the unsubstituted p
arent compound dibenzofuran as modified with empirical methoxy substit
uent parameters. Both approaches indicate that the methoxy group has a
cis conformation relative to the C-1 position, showing the potential
of using chemical shift principal values to identify certain structura
l features of polycrystalline organic samples.