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Application of NMR spectroscopy of chiral association complexes 11 —Rotation about the C(sp 2 )—C(aryl) Bond in 2,6‐Difluorobenzamides Studied by 19 F NMR
Author(s) -
Holǐk Miroslav,
Turečková Milena,
Mannschreck Albrecht,
Stühler Georgine
Publication year - 1982
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.1270190302
Subject(s) - chemistry , reagent , aryl , nuclear magnetic resonance spectroscopy , spectroscopy , coalescence (physics) , carbon 13 nmr satellite , fluorine 19 nmr , crystallography , analytical chemistry (journal) , stereochemistry , organic chemistry , physics , alkyl , quantum mechanics , astrobiology
The energy barrier to rotation about the C(sp 2 )C(aryl) single bond in non‐planar N , N ‐dimethyl‐, N , N ‐tetramethylene‐, N , N ‐diisopropyl‐2,6‐difluorobenzamides and in N , N ‐dimethyl‐2‐chloro‐6‐fluorobenzamide was investigated by 19 F{ 1 H} NMR in the presence of an optically active shift reagent. The free energy of activation was calculated from the coalescence temperature of the fluorine signals; the calculation was accomplished using the simple, approximative equation and, also, by the graphical procedure including the (eigen) line width, i.e. without the broadening caused by two‐site exchange. A distinct effect of the size of the N ‐substituents on the Δ G c ‡values was observed, in accordance with expectation.