Pure Shift 2D NMR Spectroscopy

Abstract

This chapter introduces pure shift NMR spectroscopy and shows how it can be combined with 2D methods to simplify spectra and aid interpretation. Typically, pure shift NMR is used to produce a spectrum that contains only chemical shift information in the 1H dimension, with signal overlap caused by wide multiplets removed or greatly reduced. This simplification is achieved by removing the effects of homonuclear scalar coupling. Singlet peaks, reporting only chemical shifts, are present in the 1H dimension of the final spectrum. When incorporated into 2D NMR methods, pure shift NMR can provide unparalleled spectral simplicity, removing signal overlap from 2D traces that are already the gold standard for resolution. Pure shift 2D NMR spectroscopy will be introduced through the building blocks of the commonest experiments. Pure shift implementations that exist for variants of almost all standard 2D NMR experiments will be deconstructed. The resulting components will then be used to provide a description of the concepts, theory, and practical aspects required for setting up, acquiring and processing these advanced and useful methods. There are several pure shift approaches available to the spectroscopist, each of which will be introduced and their strengths and weaknesses discussed in the context of 2D NMR. Pure shift NMR methods are not intrinsically quick to acquire. However, as pure shift methods provide direct access to spectral information that might otherwise require much more time-consuming methods they warrant a position alongside fast 2D NMR methods.