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Abstract: Here we provide examples that demonstrate the value of using properly designed and easily performed doping experiments to give insights about the nature of the analyte(s) present in a 1H NMR sample. Two mixtures, the first quite complex and the second far less so, have been chosen: (i) the crude pyrolysate from reaction of butyric acid in (supercritical) water at 600 °C and (ii) a mixture of two basic amines. In the former, 13 distinct carbonyl-containing compounds, ranging in relative concentration of nearly 2 orders of magnitude, were positively identified. The latter highlights the advantage of using a doping experiment as opposed to merely comparing the spectra from two separate samples containing the same analyte.
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Catalytic Reduction of Cinnamyl Alcohol and NMR Assessments of the Product(s)
The described laboratory experiment has been designed to introduce undergraduate students to multiple organic chemistry laboratory techniques by conducting catalytic hydrogenation of the E-isomer of cinnamyl alcohol, but without the use of compressed hydrogen gas. The combination of tetrahydroxydiboron (B2(OH)4, a solid), a tertiary amine (4-methylmorpholine, 4-MM), and 5% Pd/C allows the harvested hydrogen gas produced in situ to reduce the olefin. This protocol allows a demonstration of this powerful addition reaction that is taught early in sophomore organic chemistry, while eliminating the hazards associated with the storage and use of compressed hydrogen gas. The key laboratory techniques incorporated, besides the reaction setup, are development and visualization of thin-layer chromatograms, column chromatography over silica-gel, and solvent extraction. For product analysis, the 1H, 13C{1H}, and HMQC NMR spectra of cinnamyl and the hydrogenated hydrocinnamyl alcohols are obtained. Herein, we show two spectra of products obtained, one containing only product and the other containing an overreduction product. This provides an opportunity to discuss calculation of product ratios and to reinforce NMR spectroscopy concepts. The entire protocol would constitute activities associated with conducting a reaction, isolating, and evaluating the product. In our labs two undergraduate students, one with two semesters of undergraduate organic chemistry and the other with no prior organic chemistry laboratory experience performed the laboratory protocol and the collection and analysis of NMR data. At the end of the experiment, they were evaluated by a post-laboratory report.
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- Award ID(s):
- 1953574
- PAR ID:
- 10538647
- Publisher / Repository:
- The Chemical Educator
- Date Published:
- Journal Name:
- The Chemical Educator
- ISSN:
- 1430-4171
- Subject(s) / Keyword(s):
- catalytic reduction, hydrogen, tetrahydroxydiboron, palladium, hydrogenation
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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