Applications of benchtop NMR in the organic chemistry instructional laboratory

Abstract

The instructional organic chemistry laboratory has been substantially improved through the implementation of benchtop NMR analysis. When used in conjunction with unknown reaction components in multi-outcome experiments, NMR analysis transforms the laboratory exercise into an investigative inquiry wherein students elucidate structures for their products and thereby deduce their unknown reaction components. This analytical approach closely models the research laboratory and is a valuable preparatory tool for undergraduate researchers. Three newly developed multi-outcome experiments based upon the Diels-Alder cycloaddition, the synthesis of carboxylic amides, and the Friedel-Crafts alkylation are herein described to illustrate the utility of benchtop NMR analysis in the instructional laboratory.

Toward the Development of Rapid, Automated Identification Tests for Neat Organic Liquids Using Benchtop NMR Instrumentation

“…The large 13 C chemical shift range drastically reduces the signal dispersion problems frequently observed in 1D 1 H NMR data (see Figure 2 and additional examples in the Supporting Information). The main drawback of 13 C NMR spectroscopy is its inherently low sensitivity. However, the use of neat samples in this study allowed for short experimental times, with 1D 1 H-decoupled 13 C ( 13 C{ 1 H}) NMR experiments recorded in a few minutes.…”

“…However, the use of neat samples in this study allowed for short experimental times, with 1D 1 H-decoupled 13 C ( 13 C{ 1 H}) NMR experiments recorded in a few minutes. The signal patterns observed in 13 C{ 1 H} NMR experiments enabled the use of simplified data analysis workflows. With a suitable chemical shift referencing strategy in place (in which one of the analyte signals is automatically set as reference and the positions of the remaining signals are used as part of the acceptance criteria), only an automatic peak picking protocol is needed to establish proof of chemical identity against a reference database entry.…”

“…The test sample in neat form was added to the outer thin-wall NMR tube, whereas the inner coaxial insert was filled with the chemical shift reference material for the nuclide to be detected (or vice versa). In accordance with IUPAC recommendations, 25,26 the following reference materials were used: 1 vol % tetramethylsilane (TMS) in deuterochloroform (CDCl 3 ) for 1 H and 13 C measurements, and neat trichlorofluoromethane (CFCl 3 ) for 19 F measurements. CFCl 3 is a class I ozonedepleting substance that must be handled, stored, and disposed of in accordance with applicable regulations and laws.…”

The rise of continuous flow biocatalysis – fundamentals, very recent developments and future perspectives

“…A benchtop-NMR enables to run experiments in flow mode and it is based on the presence of permanents magnets and its main advantages are a small floor space requirement, almost zero maintenance and an easy to perform operation. [218][219][220][221][222] Often, it is used as an online detector in preparative chromatography allowing to monitor and quantify substances in an easy and rapid way. 223 5.3.2 Flow assisted synthesis technology (FAST) as industrial set-up.…”

Incorporating Benchtop NMR Spectrometers in the Undergraduate Lab: Understanding Resolution and Circumventing Second-Order Effects

“…The emergence of benchtop NMR spectrometers in the early 2010s was well-received by undergraduate laboratory instructors, as evidenced by a sharp increase in the number of academic publications which showcase feasible experiments for hands-on instrument usage − as well as within academic and industrial research. − Additionally it allowed NMR spectroscopy to be included in teaching and outreach initiatives including the Royal Society of Chemistry’s (RSC) Spectroscopy in a Suitcase (SIAS) program and the Scottish NMR User’s Group (SNUG) . Notably, Morrison and co-workers have also published several works highlighting the option for inclusion of multioutcome experiments through the use of hands-on NMR spectroscopy. , While the size, cost, and maintenance characteristics of benchtop NMR address the accessibility issues, the low-field aspect of these magnets introduces new concerns: sensitivity, resolution, dispersion, and spectral complexity.…”