A high-pressure proton nuclear magnetic resonance (NMR) probe for a stopped-flow method has been developed, which enables us to follow fast reactions at various pressures up to 200 MPa. The high-pressure stopped-flow NMR (HP-SF-NMR) method has been applied to the study of several reactions at high pressures: the reaction of tetramethyltin with iodine in chloroform and the solvent exchange reaction on aluminum(III) ion in N, N-dimethylformamide. The volumes of activation for the iodomerization of tin and the solvent exchange reaction on aluminum(III) were determined to be -24.9±3.8 cm3 mol-1 and -2.2±0.8 cm3 mol-1, respectively. The apparatus permits measurement of activation volumes for reactions with half lives longer than a few seconds if the nuclear relaxation time of the measured proton is short enough. Several requirements for the applicability of HP-SF-NMR are discussed.
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