NMR nomenclature. Nuclear spin properties and conventions for chemical shifts(IUPAC Recommendations 2001)

TLDR

Earlier recommendations on reporting chemical shifts are endorsed and the chemical shift δ is redefined to remove ambiguities while preserving practical use. The paper proposes a unified scale for reporting NMR chemical shifts of all nuclei relative to the 1 H resonance of tetramethylsilane (TMS). The unified scale defines a precise ratio Ξ between a nucleus’s resonance frequency and that of TMS in dilute chloroform, discusses referencing procedures, lists recommended reference samples and Ξ values for secondary references, relates the scale to aqueous‑solution and solid‑state magic‑angle‑spinning protocols, and tabulates standardized nuclear‑spin data (quantum numbers, abundances, magnetic moments, magnetogyric ratios, receptivities, quadrupole moments, and line‑width factors) for stable and some unstable isotopes. The authors issue nine new recommendations concerning chemical shifts.

Abstract

Abstract A unified scale is recommended for reporting the NMR chemical shifts of all nuclei relative to the 1 H resonance of tetramethylsilane (TMS). The unified scale is designed to provide a precise ratio, Ξ , of the resonance frequency of a given nuclide to that of the primary reference, the 1H resonance of TMS in dilute solution (volume fraction, φ < 1%) in chloroform. Referencing procedures are discussed, including matters of practical application of the unified scale. Special attention is paid to recommended reference samples, and values of Ξ for secondary references on the unified scale are listed, many of which are the results of new measurements. Some earlier recommendations relating to the reporting of chemical shifts are endorsed. The chemical shift, δ , is redefined to avoid previous ambiguities but to leave practical usage unchanged. Relations between the unified scale and recently published recommendations for referencing in aqueous solutions (for specific use in biochemical work) are discussed, as well as the special effects of working in the solid state with magic-angle spinning. In all, nine new recommendations relating to chemical shifts are made. Standardized nuclear spin data are also presented in tabular form for the stable (and some unstable) isotopes of all elements with nonzero quantum numbers. The information given includes quantum numbers, isotopic abundances, magnetic moments, magnetogyric ratios and receptivities, together with quadrupole moments and line-width factors where appropriate.