Abstract

Hindered pyramidal inversion and restricted rotation in N-propyl-N-(4-pyridyl)-1-amino-1H-pyrazole were studied by dynamic NMR spectroscopy and molecular modelling. From lineshape analyses of two sets of signals by H-1 NMR, thermodynamic parameters were obtained (Delta G, Delta H, and Delta S). The molecular modelling studies allowed us to assign the contribution of both nitrogen inversion (12.3 kcal mol(-1)) and N-C rotation (2.7 kcal mol(-1)) to the enthalpy of the energetic barrier. (C) 2000 Elsevier Science Ltd. All rights reserved.