Indirect nuclear Overhauser enhancements through 19F have been determined for the three‐spin systems 1H‐19F‐1H and 1H‐19F‐13C by steady‐state presaturation of the appropriate proton, and applied to the conformational analysis of 5‐bromo‐2‐fluoro‐4‐nitroacetanilide. The 1H NOE difference spectra at 400 MHz showed antiphase doublets for protons undergoing simultaneous dipolar relaxation with, and scalar coupling to, 19F. Similarly, in the 13C 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. Copyright © 1987 John Wiley & Sons Ltd.
|Journal||Magnetic Resonance in Chemistry|
|Publication status||Published - 1 Jan 1987|
- 1 19 1 1 19 13 H‐ F‐ H and H‐ F‐ C systems
- Anomalous intensity effects
- Conformational analysis
- Indirect heteronuclear NOEs
- Three‐spin effects