Chapter 9 - Correlations Through Space: The Nuclear Overhauser Effect

Abstract

This chapter is subdivided into two parts which separate the theoretical description of the nuclear Overhauser effect (NOE) from the practicalities of its observation. Part I begins by introducing the physical basis of the NOE, progressing from a simple two-spin up to multi-spin system. It explains the concepts of transient, steady-state and rotating frame NOEs and defines where these measurements are most appropriate. Part II describes experimental techniques that may be employed in the observation and measurement of the NOE, including 1D and 2D NOE spectroscopy (NOESY) and rotating frame NOE spectroscopy (ROESY) methods for homonuclear spin systems, and heteronuclear Overhauser effect spectroscopy (HOESY) techniques for the measurement of heteronuclear NOEs. It briefly considers how 2D methods closely related to NOESY may be used to study slow chemical exchange spectroscopy (EXSY) processes. Finally, it describes the use of residual dipolar couplings to determine the relative orientations of bond vectors in molecules, as a complementary route to stereochemical definition.