"NMR Spectroscopy"

J. W. Rathke, R. J. Klingler, R. E. Gerald II, D. E. Fremgen, K. Woelk, and C. J. Elsevier, in "Chemical Synthesis Using Supercritical Fluids", P. G. Jessop and W. Leitner (Eds.), 165-194, Wiley-VCH, Weinheim (1999).

• This section describes high-pressure NMR studies conducted in supercritical fluid reaction media.

• Most of this research was performed in the various research programs of the several authors of this review, namely, the Fluid Catalysis and Ion Transport Programs at Argonne National Laboratory, the In Situ NMR Spectroscopy and Rotating-Frame Microscopy Program at the University of Bonn, and the NMR and Catalysis in Supercritical Media Program at the University of Amsterdam.

• Although much of the described research was performed with metal toroid probes, or with single-crystal sapphire high-pressure NMR cells, which even together represent only a small subset of the available probe designs, the cited experiments are intended to provide at least a representative sampling of the great diversity of measurements that have already been attempted in supercritical media.

• It should also be noted that this review is less focused on probe design (for which a number of high-quality reviews have recently appeared), but instead it concentrates on design for only two device types (namely, toroid probes and sapphire NMR cells) and then focusses more on the type of measurements and observations that a synthetic chemist might encounter if he chooses to use NMR to explore reaction chemistry or to measure reaction parameters in supercritical fluids.

• The unusual properties of supercritical fluids that make them attractive reaction media can sometimes also manifest themselves in unusual (and surprising) NMR effects that can be extremely useful in the hands of the wary, and confounding in the hands of the unwary researcher.

K. Woelk, September 25, 2000