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The relationship between 19 F substituent chemical shifts and electron densities: meta ‐ and para ‐substituted benzoyl fluorides
Author(s) -
Brownlee Robert T. C.,
Craik David J.
Publication year - 1980
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.1270140308
Subject(s) - substituent , chemistry , chemical shift , fluorine , electron density , atom (system on chip) , electron , density functional theory , crystallography , medicinal chemistry , computational chemistry , organic chemistry , physics , quantum mechanics , computer science , embedded system
The 19 F substituent chemical shifts (SCS) of meta ‐ and para ‐benzoyl fluorides are found to correlate well with substituent parameters using the dual substituent parameter (DSP) equation, indicating that they reflect electronic perturbations induced by the substituent. The direction of the SCS values is such that donating substituents cause upfield shifts whilst acceptors cause downfield shifts. STO‐3G calculations indicate that substituents induce only very small changes in π‐electron density about the fluorine atom, but that these changes correlate reasonably well with the observed SCS values. For the para series, the slope of the relationship between δq π Fand 19 F SCS is 5000 ppm/electron, indicating the great sensitivity of the flourine atom to small changes in electron density.