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Carbon-13 nuclear magnetic resonance spectroscopy—VII:para-substituted fluorobenzenes

✍ Scribed by Goh Miyajima; Hiromichi Akiyama; Kichisuke Nishimoto

Publisher
John Wiley and Sons
Year
1972
Tongue
English
Weight
598 KB
Volume
4
Category
Article
ISSN
0749-1581

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✦ Synopsis

Abstract

C‐13 and F‐19 NMR spectra of seventeen para‐substituted fluorobenzenes were measured and the chemical shifts as well as coupling constants with respect to substituents were analysed. The chemical shifts of the fluorine, the C~1~ and the C~2~ atoms were found to depend on the total electron densities. In the case of the C~3~ atom, the chemical shifts seem to depend on π‐electron densities rather than the total electron densities. The present calculations also indicate that the chemical shift of the C~4~ atom depends mainly on σ‐electron densities due to the inductive effects of substituents. The strongest factor influencing the coupling constant, ^n^J(CF), is also considered to be the π‐electron densities on the carbon atoms. In the case of the direct couplings, ^1^J(CF), the π‐bond orders are important.

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