Premium
Indirect 1 H 19 F 1 H and 1 H 19 F 13 C nuclear overhauser enhancements: Anomalous intensity effects and applications in conformational analysis
Author(s) -
SánchezFerrando Francisco,
Sanders Jeremy K. M.
Publication year - 1987
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.1260250617
Subject(s) - chemistry , proton , nuclear overhauser effect , carbon 13 , spectral line , analytical chemistry (journal) , relaxation (psychology) , dipole , nuclear magnetic resonance , nuclear magnetic resonance spectroscopy , stereochemistry , physics , nuclear physics , psychology , social psychology , organic chemistry , chromatography , astronomy
Indirect nuclear Overhauser enhancements through 19 F have been determined for the three‐spin systems 1 H‐ 19 F‐ 1 H and 1 H‐ 19 F‐ 13 C by steady‐state presaturation of the appropriate proton, and applied to the conformational analysis of 5‐bromo‐2‐fluoro‐4‐nitroacetanilide. The 1 H NOE difference spectra at 400 MHz showed antiphase doublets for protons undergoing simultaneous dipolar relaxation with, and scalar coupling to, 19 F. Similarly, in the 13 C selective NOE difference spectrum at 100 MHz, the two lines of the fluorine‐bearing carbon showed negative enhancement factors of different magnitude on presaturation of the appropriate proton. The use of these anomalous intensity effects in conformational analysis is illustrated.