A First Laboratory Utilizing NMR for Undergraduate Education: Characterization of Edible Fats and Oils by Quantitative ¹³C NMR

Abstract

Quantitative 13 C NMR provides a straightforward method of analyzing edible oils in undergraduate chemistry laboratories. 13 C spectra are relatively easy to understand, and are much simpler to analyze and workup than corresponding 1 H spectra. Average chain length, degree of saturation, and average polyunsaturated fatty acid content of common edible oils are obtained directly using integrals of the proper regions in the 13 C 1D spectra. These spectra segue to 2D 1 H− 13 C HSQC experiments that provide an excellent path for students to verify assignments, in particular those associated with polyunsaturated fatty acids. Data acquisition and analysis can be completed in one to two lab sections, although spectrometer scheduling may be necessary for groups of students greater than six. 13 C relaxation measurements of common oils are presented that enable accurate quantitative 13 C data to be obtained in reasonable amounts of time (30−40 min per sample) on modern 400 MHz NMR spectrometers.

Learning H-Coupled 13C NMR in the First Month of Sophomore Organic Lecture

“…While there has been much discussion [13][14][15][16][17][18][19][20][21][22][23][24][25][26] of the use of 13 C NMR in the sophomore organic course -Chamberlain 23 in particular nicely summarized the reasons to teach 13 C NMR before 1 H NMR -this has mostly focused on the laboratory portion of the course, or on advanced [27][28][29][30][31][32][33][34][35] coursework. Instruction in elementary 13 C NMR from the beginning of the lecture course can equip the student with the tools necessary to solve simple structural problems.…”

Brewing alcohol 101: An undergraduate experiment utilizing benchtop NMR for quantification and process monitoring

“…8 While accessible, benchtop NMR in undergraduate lab settings are still underutilized, and most often used for traditional structure elucidation. 9-13 A few experiments have been created that examine other facets of NMR spectroscopy, but most have focused on physical chemistry, [13][14][15][16][17][18][19] leaving experiments teaching proper analytical techniques somewhat lacking. In fact, only two experiments that explored quantitative NMR at low-field were found in the educational literature, one was specific to 13 C NMR and was a subset of a greater experiment focused on structure characterization, 14 the other was structure elucidation of a mixture with a small sub-component on quantification.…”

Capturing the Precise Structure of Liquids: The Crystalline Sponge Method for an Undergraduate Laboratory Course

“…The molecular structure of an organic compound is intrinsically related to its properties, making structural elucidation a vital aspect of chemical research and product development. As a result, many techniques are taught in undergraduate curricula for determining structures of organic compounds, such as MS, FTIR, and NMR. − These methods provide important structural information such as molecular formula and connectivity of atoms. However, the as-obtained molecular structures are, strictly speaking, speculative and may not always be reliable. − SC-XRD provides unambiguous and accurate 3D structural parameters and is the most reliable technique for molecular structure determination. , However, SC-XRD is intrinsically limited to molecules that are crystalline and, therefore, traditionally precludes the analysis of liquid compounds.…”