HIGH-PRESSURE STOPPED-FLOW NUCLEAR-MAGNETIC-RESONANCE APPARATUS FOR THE STUDY OF FAST REACTIONS IN SOLUTION

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.