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Carbon‐13 nuclear magnetic resonance spectroscopy—VII: para ‐substituted fluorobenzenes
Author(s) -
Miyajima Goh,
Akiyama Hiromichi,
Nishimoto Kichisuke
Publication year - 1972
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.1270040605
Subject(s) - chemical shift , coupling constant , chemistry , fluorine , atom (system on chip) , electron density , resonance (particle physics) , electron , carbon atom , atomic physics , spectral line , spectroscopy , carbon fibers , chemical bond , computational chemistry , physics , materials science , ring (chemistry) , organic chemistry , particle physics , quantum mechanics , astronomy , composite number , computer science , composite material , embedded system
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 (CF), is also considered to be the π‐electron densities on the carbon atoms. In the case of the direct couplings, 1 J (CF), the π‐bond orders are important.