Chemical Education Today
NSF Highlights Projects Supported by the NSF Division of Undergraduate Education
The Influence of Modern NMR Spectroscopy on Undergraduate Organic, Inorganic, and Physical Chemistry at Florida State University by Joseph B. Vaughn, Jr.
Our proposal “Nuclear Magnetic Resonance Instrumentation for Undergraduate Chemistry Laboratory: Development and Implementation” was funded by the Instrumentation and Laboratory Improvement (ILI) program in 1999. Prior to that, NMR instruction in the undergraduate chemistry laboratories at Florida State University was very primitive and of minimal NMR educational value. Instruction consisted of a presentation of NMR simulations on Macintosh SE computers available to the organic chemistry labs and two physical chemistry lab experiments taken from “Pulse and Fourier Transform NMR” (1). The physical chemistry (pchem) lab experiments were the determination of keto-enol equilibrium constants, and longitudinal and transverse relaxation times. The organic lab program, NMR Simulator (2), simulated a Varian EM360, a 1975 vintage 60 MHz continuous wave spectrometer. It was as equally frustrating to operate as that spectrometer. Although the program gave the students the opportunity to plot data and identify a “paper unknown”, it was significantly removed from the actual content of the organic laboratory course. It provided the students with no feedback about structure and purity of their own synthetic efforts. The physical chemistry labs used data acquired by the NMR facility staff using a 300 MHz spectrometer to determine the keto-enol equilibrium constants. The pchem lab also used a very low field electromagnet with controls purchased from Teach Spin (3) to determine longitudinal and transverse relaxation times of an aqueous CuSO4 sample using the inversion-recovery pulse sequence and the Hahn spin-echo pulse sequence (4). It was a situation that desperately needed to be remedied. Integrating an NMR Spectrometer into the Curriculum The remedy has been provided by the purchase of a Varian Inova 300 MHz NMR spectrometer that was installed in November 1999 and began acquiring data for the organic, physical, and inorganic chemistry labs in the spring semester of 2000. It is configured with two full band (15N–1H) radio frequency (rf ) channels, z-axis pulsed field gradient (PFG), waveform generator on one rf channel, phase modulator, automatic 2H gradient shimming, variable temperature (VT) control and a 5 mm four channel (1H, 13C, 15N, 31P) z-axis PFG probe. The probe can be used in a broad band configuration (15N–31P) by use of external capacitors. It is also configured with an automatic robot sample handler. The robot was chosen over the proposed flow probe after viewing two demonstration sites. Although the flow probe performed extremely well in those well-controlled environments, it was felt that the flow lines presented a great potential for frequent 306
clogging due to unpredictable quality of sample preparation. In fact after several weeks of operation, it was clear that this was a legitimate concern. Students in the organic chemistry labs have submitted many samples with solid materials that would certainly clog the flow probe lines. Initial results from the implementation of this project have been presented at several seminars (5). One of these PowerPoint slide presentations can be found on the Web page of the Undergraduate NMR Facility (6). A teaching assistant (TA) has been assigned to this project and operates the spectrometer for the samples submitted by students in the undergraduate organic and inorganic laboratories. The organic labs consist of four to six sections of sixteen students. The students access their NMR data via the 46 NT workstations in the Undergraduate Computer Lab.1 The UNIX server2 running Varian NMR software is remotemounted on the spectrometer host computer, and data are stored automatically in the student’s account. I present the instruction for processing the data via a LCD overhead projector, and I distribute a step-by-step tutorial prior to that instruction. Additionally, the entire tutorial is presented on the Undergraduate NMR Facility Web site (6). The inorganic lab students submit samples and receive spectra plotted with expansions and integrals. Because they will have learned to do so in organic lab, we will have them process their own data in the spring 2002 semester. Thus far we have observed only protons for the organic and pchem labs. We may include 13C in the future for the organic labs. For the inorganic labs we have observed 1H, 13C, 31P, and 19 F in a variety of transition metal complexes. The TA provides assistance to the pchem students. Those students are provided hands-on access to the spectrometer to perform their NMR experiments. I present the instruction for their use of the spectrometer. I have prepared automation macros and distribute a complete step-by-step tutorial prior to that instruction. This tutorial is also presented on the Undergraduate NMR Facility Web site (6 ). Those students determine the keto-enol equilibrium constants of acetylacetonate in C6D6 and ethylacetylacetonate in CD3OD by doing a VT experiment and using the integral ratios of appropriate resonances in the spectra. We have now completed nearly six semesters (two calendar years) of operation. There have been very few hardware problems, and these did not adversely impact the spectra provided to the students. Impact of the Project The stated goal in the proposal reads: “The excitement of working with state-of-the-art equipment is a very impor-
Journal of Chemical Education • Vol. 79 No. 3 March 2002 • JChemEd.chem.wisc.edu
Chemical Education Today edited by
Susan H. Hixson National Science Foundation Arlington, VA 22230
Richard F. Jones Sinclair Community College Dayton, OH 45402-1460
Strongly Agree
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Having state-of-the-art NMR spectra available 1. Improved my understanding of my synthetic efforts:
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2. Made a significant positive contribution to my experience with technology:
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3. Stimulated my interest in chemistry:
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5. Provided an excellent evaluation of the purity of my sample and thus the quality of my synthetic efforts in the laboratory:
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6. Challenged me intellectually:
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4. Was more stimulating than having to learn it from a book:
tant factor in attracting students to scientific careers. Providing that excitement and thereby attracting students to science is the primary goal of this project.” We have provided that experience to our undergraduate organic, inorganic, and pchem lab students. The pchem students get hands-on experience in acquiring their data. By having access to an NMR spectrum of an actual product, the organic and inorganic students learn how well they are performing at the bench. It provides an assessment of their technique and reinforces the NMR spectroscopic theory taught in the lecture of the class. By following the conversion of functional groups or the stepwise synthesis of a molecule, students strengthen their understanding of NMR spectroscopy and its intimate relationship to chemistry. I have developed and distributed evaluation questionnaires at the end of each semester. There has been a 100% response because we give 5 points on the final exam for those that are returned. Some statements and response totals are shown in the box at the top of the page. One of the best comments to the request to “Describe what you liked most about the NMR part of the course” was: “Pay no attention to those who complain. This is a great project.” The most common response to “Describe what you liked least about the NMR part of the course” was: “It takes too much time.” The results of the student surveys have shown that we have been successful in achieving our stated goal. In particular, the survey reveals that the large majority of students are more attracted to science because of the experience provided by this project. Next semester, access to this instrument will be extended to the organic chemistry laboratory at Tallahassee Community College. In the future we hope to use it to offer a new NMR Applications Laboratory course to advanced undergraduates.
Acknowledgments Partial funding for this project was provided by the National Science Foundation’s Division of Undergraduate Education, Instrumentation and Laboratory Improvement Program, Grant No. DUE-9972198. The Florida State University and the Department of Chemistry and Biochemistry provided matching funds. Notes 1. We acknowledge the support of NSF ILI grant DUE 9751465 for funding this project. 2. The UNIX server for the spectrometer is a SUN Enterprise 250 with two, 20-Gbyte drives and 2 Gbytes of RAM.
Literature Cited 1. Farrar, T. C.; Becker, E. D. Pulse and Fourier Transform NMR; Academic: New York, 1971. 2. Schatz, P. NMR Simulator, Macintosh Version 2.0.1, Trinity Software Publishing, 1988. 3. Teach Spin, Inc., 45 Penhurst Parkway, Buffalo, NY 14222. 4. Hahn, E. L. Phys. Rev., 1950, 80, 580–594. 5. Vaughn, J. B., Jr. Integration of a State-of-the-Art NMR Spectrometer into Undergraduate Chemistry Laboratories and Preliminary Project Evaluation, Seminar presentation, St. John’s University’s Symposium: NMR Spectroscopy: State-of-the-art Applications from Undergraduate Education, Graduate Education and Industry, November 7, 2000. 6. http://www.chem.fsu.edu/ungrad/NMR/ (accessed Jan 2002).
Joseph Vaughn is in the Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL 32306;
[email protected].
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