Essential Terminology Connects NMR and qNMR Spectroscopy to Its Theoretical Foundation


Classical 1D 1H NMR spectra are prototypic for NMR spectroscopy in that they represent a wealth of chemical information encoded into convoluted graphs or patterns that contain complex features (aka multiplets), even for seemingly simple molecules. Accordingly, the utility of NMR depends on the theoretical and visual skills required to extract all the physical parameters that represent usable structural and quantitative information. Moreover, it depends on the ability of the analyst to communicate them effectively and reproducibly. After decades of continuous development, NMR spectroscopy has reached a stage where its analytical capabilities have outgrown the typical level of detail of interpretation, especially of 1D NMR spectra. The quantum-mechanical (QM) foundation, history, evolution, and (in-)consistency of widely applied terminology calls for re-examination and recalibration. In order to develop new perspectives on solution-state NMR analysis, including the rapidly evolving quantitative NMR (qNMR), the present study draws on the well-established NMR model systems and molecules (AB2C2, strychnine, testosterone, α-santonin). Through well-documented key topics related to spectral acquisition and analysis, the study builds the foundation for a modular, coherent, and standardized nomenclature of NMR terminology. This is a necessary condition for a healthy research data lifecycle including their management and reuse. This work presents experimental evidence and connects with essential concepts of QM theory that clarify the distinct meaning of the primary terms: resonance, signal, pattern, peak, line, transition; as well as other widely used terms: splitting, multiplicity/multiplet, resolution, and dispersion. The proposed NMR terminology was built through a consensus-finding process that evolved from extended pharmacopoeial and research coordination efforts. It is supported by detailed figures and NMR data interpretation that employs QM-based full spin analysis.