5-MEMBERED RING ROTATIONS, PSEUDOROTATIONS, AND HYDROGEN-BOND EXCHANGE DYNAMICS IN THE SOLID-STATE STUDIED BY NMR-SPECTROSCOPY

C-13 CP/MAS NMR studies were carried out on trans-1,2-cyclopentanediol , on 4,4-dimethyl-trans-1,2-cyclopentanediol, and on sulfolane at vari able temperatures. The spectra showed evidence of three dynamic solid- state processes: hydrogen bond exchange, ring pseudorotation, and whol e molecule rotations about local C-2 axes. Fitting of T-1 rho data to calculated values of the C-13-H-1 dipolar interactions allowed differe ntiation between ring pseudorotations and whole molecule C-2 reorienta tions. Isotopic H-1/H-2 substitution demonstrated the existence of hyd rogen bond exchange processes in the diols. Activation parameters for these processes were derived from both coalescence measurements and th e T-1 rho measurements.