JCE_Accepted_Proof_11th_July_2019.pdf (2.12 MB)
Benchtop NMR spectroscopy and spectral analysis of the cis- and trans-stilbene products of the Wittig reaction
journal contribution
posted on 2019-10-10, 10:56 authored by Mark Edgar, Benita C Percival, Miles Gibson, Jinit Masania, Ken Beresford, Philippe B Wilson, Martin GrootveldABSTRACT: Benchtop NMR spectrometers are now becoming more widely employed in university teaching laboratories. These low-field instruments are increasingly used in reaction monitoring and product purity applications. NMR spectra obtained using these spectrometers (40−80 MHz) tend to suffer from significant overlap of signals when compared to those obtained at 300−400 MHz or above, and therefore, some reactions may be less suited to analysis using such benchtop systems. While some reactions can be modified to make them more amenable to analysis on low-field benchtop spectrometers, the fact remains that many common undergraduate laboratory chemistry reactions remain as a stalwart of the university education system. Therefore, there is currently a major requirement for benchtop NMR analysis to improve in order to facilitate student understanding. Herein, it is demonstrated that a combination of spectral analysis and simulation at low-fields (40−80 MHz) allows the fine structure of second-order effects and overlapping spectra to be deduced, enabling an improved understanding of the low-field benchtop NMR technique within undergraduate student cohorts. The evolution of well-resolved and distinct multiplets at 400 MHz to complex, overlapping multiplets at 40−80 MHz also serves as a useful guide for laboratory demonstrators and academic staff when explaining the advantages of such benchtop systems. The Wittig reaction has been a standard reaction practical session in many university teaching laboratories since the 1980s, the products of which are a mixture of cis- and trans-stilbenes. This reaction serves as an ideal example of how benchtop NMR spectrometers and analysis can support chemistry teaching laboratories.
History
School
- Science
Department
- Chemistry
Published in
Journal of Chemical EducationVolume
96Issue
9Pages
1938 - 1947Publisher
American Chemical Society (ACS)Version
- AM (Accepted Manuscript)
Rights holder
© American Chemical SocietyPublisher statement
This document is the Accepted Manuscript version of a Published Work that appeared in final form in Journal of Chemical Education, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see https://doi.org/10.1021/acs.jchemed.8b00657Acceptance date
2019-07-16Publication date
2019-07-16Copyright date
2019ISSN
0021-9584eISSN
1938-1328Publisher version
Language
- en