A Modular Rapid-Injection NMR for Structure Elucidation and Kinetic Analysis

Abstract Rapid-injection nuclear magnetic resonance (RI-NMR) spectroscopy transforms a standard NMR tube into a reaction vessel within the NMR spectrometer, enabling kinetic and spectroscopic characterization of intermediates under synthetically relevant conditions. Despite its versatility as a tool for mechanistic analysis, the broad adoption of RI-NMR has been hindered by the lack of cost- and space-efficient instrument designs, which can be operated with negligible interference to the NMR facility. Herein, we describe an RI apparatus that is compatible with most NMR spectrometers, requires no modification of the NMR instrument or probe, and may be easily transported to and from the laboratory. Accurate reagent delivery is achieved across a range of solvents and temperatures, and samples can be mixed within seconds after injection. The utility of this apparatus is highlighted through four case studies chosen to illustrate different aspects of the instrument.