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Indirect 1H19F1H and 1H19F13C nuclear overhauser enhancements: Anomalous intensity effects and applications in conformational analysis

✍ Scribed by Francisco Sánchez-Ferrando; Jeremy K. M. Sanders

Publisher: John Wiley and Sons
Year: 1987
Tongue: English
Weight: 389 KB
Volume: 25
Category: Article
ISSN: 0749-1581
DOI: 10.1002/mrc.1260250617

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✦ Synopsis

Indirect nuclear Overhauser enhancements through 19F have been determined for the three-spin systems 'H-I9F-'H and 1H-'9F-'3C by steady-state presaturation of the appropriate proton, and applied to the conformational analysis of 5-bromo-2-fluoro-4-nitroacetanilide. The 'H NOE difference spectra at 400 MHz showed antiphase doublets for protons undergoing simultaneous dipolar relaxation with, and scalar coupling to, I9F. 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.

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