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Inhibition and enhancement of resonance as studied by 13C nuclear magnetic resonance spectroscopy

✍ Scribed by William Kitching; Ian De Jonge; William Adcock; Anil N. Abeywickrema

Publisher
John Wiley and Sons
Year
1980
Tongue
English
Weight
869 KB
Volume
14
Category
Article
ISSN
0749-1581

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✦ Synopsis

Abstract

^13^C chemical shifts are reported for a series of 2‐substituted 1,3‐dimethylbenzenes: comparisons of these values with those for the corresponding monosubstituted benzenes reveal, in some cases, large differences in the para‐carbon substituent chemical shifts, which are attributable to steric hindrance of resonance. The questions of steric enhancement of resonance, and methoxy group conformation in certain anisoles are also studied by the ^13^C NMR technique. Studies of selected 2‐substituted fluorenes are also reported, and substituent chemical shifts at carbon‐7 (traversing eight bonds) of greater than 2ppm are observed. These effects are consistently greater than those reported for the corresponding biphenyl compounds, and are associated with planarity‐enforced enhancement of resonance.

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