8. NMR Chemical Shift Calculations
NMR spectroscopy is one of the most important analytical tools for solution phase chemistry. The significance of NMR spectroscopy is based on its ability to distinguish a particular nucleus with respect to its molecular environment. Key parameters obtained from experimental spectra are the chemical shifts of NMR active nuclei as well as their coupling parameters with the respective neighbours. In the following we will focus on the theoretical calculation of isotropic shielding values as a measure of different chemical environments (Calculation of NMR Isotropic Shieldings) and their correspondence with experimentally measured chemical shifts (Conversion of Isotropic Shieldings to Chemical Shifts and Positional Averaging of Shielding Values). The accuracy of NMR chemical shift predictions benefits substantially from selecting appropriate (that is: specifically optimized) basis sets and chemically related reference systems.