Implementation of Earth’s Field NMR Spectroscopy in an Undergraduate Chemistry Laboratory

Abstract

Earth's field nuclear magnetic resonance (EFNMR) spectroscopy offers students a unique opportunity to consolidate their understanding of NMR spectroscopic theory through hands-on practice with a simple spectrometer. A comprehensive, six-hour experiment is presented for the introduction of lowfield NMR techniques, covering spectroscopy, relaxivity, and imaging experiments in the Earth's magnetic field. This multi-faceted practical session explored the concepts of free induction decay, pulse sequences, field homogeneity, relaxation times, J-coupling, and magnetic resonance imaging (MRI), reinforced through a series of experiments carried out within an undergraduate teaching laboratory. Students are required to alter parameters as they see fit in order to obtain data, ensuring their understanding of the theory behind NMR spectroscopy. The challenges overcome for the implementation of EFNMR spectroscopy in a modern undergraduate laboratory are also discussed and detailed instructions included for spectrometer set up.

Chemical Analysis of Fluorobenzenes via Multinuclear Detection in the Strong Heteronuclear J-Coupling Regime

“…Despite the wealth of information available in the strong heteronuclear J-coupling regime, the JCS of only 22 compounds have been published to the best of our knowledge, and a majority of these studies have focused on six different heteronuclear spin systems, such as 11 B- [19], 13 C- [15,16,24,25,43], 14 N- [19,26,36], 19 F- [17,18,21,23,25,[27][28][29][30][31][32][33][34][35][36], 29 Si- [16,17], and 31 P-1 H [15,22,[25][26][27]29,[37][38][39][40][41], and the majority of these compounds do not contain homonuclear J-couplings. The lack of systematic study and subsequent application may be a result of the decreased sensitivity of low-magnetic fields, even with modest prepolarization techniques, which require large spin densities and sample volumes (mL samples, neat concentrations).…”