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Influence of gauche interactions on the substituent effects on carbon-13 chemical shifts in six-membered ring compounds

✍ Scribed by K. Pandia Rajan; A. Manimekalai

Publisher
John Wiley and Sons
Year
1991
Tongue
English
Weight
487 KB
Volume
29
Category
Article
ISSN
0749-1581

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✦ Synopsis

Abstract

^13^C NMR spectra of six epimeric substituted 4‐hydroxypiperidines and two corresponding piperidines were recorded. Substituent parameters for equatorial methyl, gem‐dimethyl, equatorial hydroxy and axial hydroxy groups were calculated from the ^13^C chemical shifts of these compounds and several other six‐membered ring compounds. The effects of nearby substituents on these parameters were examined. It is concluded that the magnitude and even the sign of the α effect is modified by the presence of nearby substituents. It was found that gauche interactions play an important role in determining the magnitude of the α effect. However, the β effect is not influenced by the nearby substituents except for the gem‐dimethyl group. The magnitude of the γ effect is almost independent of the nearby substituents.

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