N.M.R. Measurements of Reaction Velocities and Equilibrium Constants as a Function of Temperature

Abstract

Publisher Summary This chapter reviews the information obtained about organic molecules from the temperature dependence of their nuclear magnetic resonance (NMR) spectra. The parameters obtained from the study of NMR spectra include chemical shifts, nuclear spin–spin coupling constants via electrons, and nuclear relaxation times. The chapter also describes the connection between reaction velocities and NMR spectra. NMR methods can be applied to study all atoms that make up organic molecules, such as H 1 , H 2 , H 3 , and F 19 . Many of these nuclei are present in low natural abundance and some have, apart from a nuclear magnetic moment, a nuclear electric quadrupole moment. The nuclei of chlorine, bromine, and iodine occur in good natural abundance with a favorable nuclear magnetic moment, but they are less popular, because the signals are broad owing to the effects of nuclear electric quadrupole moments. The electric-field gradients near a halogen nucleus are invariably large in organic molecules, because they occur at the periphery of the molecule in a univalent state, leading to short relaxation times and consequent broad signals.