Nuclear Overhauser effects arising from the interactions of spins of solvent molecules with spins of a solute should reveal the "exposure" of solute spins to collisions with solvent. Such intermolecular NOEs could, therefore, provide information regarding conformation or structure of the solute. Determinations of solute-solvent NOEs of 1,3-di-tert-butylbenzene in solvents composed of perfluoro-tert-butyl alcohol, tetramethylsilane, and carbon tetrachloride have been carried out. A crude, but apparently reliable, method for prediction of intermolecular solvent-solute NOEs based on hard (noninteracting) spheres was developed. Comparison of experimental to predicted NOEs indicates that tetramethylsilane interacts with the solute according to the model. By contrast, intermolecular NOE data indicate attractive interactions between the solute and perfluoro-tert-butyl alcohol. All NOE results and the corresponding predictions confirm that proton H2 of the solute is protected by the flanking tert-butyl groups from interactions with solvent molecules.

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Fluorine NMR spectroscopy has been used to identify and quantitate metabolites of profluralin appearing in the urine of rats postingestion of the herbicide. The chemical shift of the trifluoromethyl group was shown to be a useful indicator of the chemical type of metabolite, and the shifts for the classes of materials previously identified as metabolites have been determined. By use of chemical shift criteria this work provides evidence for several metabolites that have not been recognized in previous work; some of these remain incompletely characterized. Though the number and types of metabolites detected in the urine were consistent from animal to animal, the time course for appearance of metabolites was found to be animal dependent.

4-(Trifluoromethyl)-alpha-bromoacetanilide is structurally similar to a large number of compounds that inactivate alpha-chymotrypsin by alkylating the methionine-192 residue or occasionally serine-195. Fluorine nuclear magnetic resonance (NMR) experiments suggest that this material reacts with the enzyme at two distinct loci. One of these involves alkylation of methionine while reaction at a second site, which does not appear to be near the active site, diminishes the proclivity for reaction at methionine. Solvent effects (H2O/D2O) and fluorine-proton Overhauser experiments indicate that the reporter group attached to methionine closely contacts the protein surface and is thereby shielded from solvent while the CF3 group at the second site is more accessible to solvent.

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