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Substituent shielding parameters of fluorine‐19 NMR on polyfluoroaromatic compounds dissolved in dimethyl sulphoxide‐ d 6
Author(s) -
Ando Shinji,
Matsuura Tohru
Publication year - 1995
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.1260330805
Subject(s) - chemistry , substituent , fluorine , fluorine 19 nmr , deuterium , electromagnetic shielding , chloroform , nmr spectra database , organic chemistry , medicinal chemistry , nuclear magnetic resonance spectroscopy , spectral line , physics , quantum mechanics , astronomy , electrical engineering , engineering
High resolution fluorine‐19 NMR spectra of polyfluoroaromatic compounds dissolved in deuterated dimethyl sulphoxide were measured and substituent shielding parameters were derived. These parameters were compared with the values observed in deuterated chloroform solutions and used to identify fluoroaromatic compounds related to perfluorinated polyimides and poly(amic acids)s. Average differences of Δδ between the solvents are 1.1, 1.0 and 2.1 ppm for o ‐, m ‐ and p ‐fluorines of monosubstituted pentafluorobenzenes, respectively. The significant difference for p ‐fluorine of NH 2 is important in identifying perfluorinated diamines because they are source materials for perfluorinated polyimides. Substituent shielding parameters for meta and para substitution increase as the respective Hammett σ constants increase, which indicates that fluorine‐19 NMR chemical shift is primarily determined by electron density.