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WebSpectra: Online NMR and IR Spectra for Students Craig A. Merlic,* Barry C. Fam, and Michael M. Miller Department of Chemistry and Biochemistry, University of California at Los Angeles, Los Angeles, CA 90095-1569; *
[email protected] Structure is absolutely critical when teaching organic chemistry. It forms the basis of predicting and rationalizing reactivity on the molecular scale and physical properties at the macroscopic level. The standard approach for teaching organic structure begins with orbitals and progresses through conformations, stereochemistry, and functional groups. Then spectroscopy, in particular nuclear magnetic resonance (NMR) and infrared (IR) spectroscopies, is introduced as a means of determining organic structures (1). This is essential material, as NMR is the single most important structural tool for the modern organic chemist. Students find the discussion on spectroscopy intriguing, yet daunting (2). However, the real challenge for students learning to determine organic structures with spectroscopic data is not the concepts, but the limited number of spectra available with which to practice analyzing. Solving spectral problems is just not something that can be learned from reading; only practice interpreting real spectra suffices. Most organic textbooks have a very limited number of spectral problems, and while compilations of spectral problems exist, the cost per problem is often prohibitive for students. For schools with the resources of in-house spectrometers, one solution has been local acquisition of spectra followed by massive paper copying. The ultimate solution, of course, is free online spectral archives and this is now a reality. Computers and the World Wide Web (WWW) in particular have become important and powerful tools for teaching chemistry (3, 4). WebSpectra is a WWW site implemented at UCLA (http://www.chem.ucla.edu/webspectra).1 Through this site, students have convenient and free access to a library of problems in NMR and IR spectroscopy, ranging in difficulty from introductory to advanced. An important feature is that expansions of the high-resolution spectra can be controlled by the user. The site also includes instructional materials and tools to assist students in learning about NMR and IR spectroscopy. The design and capabilities of this Web-based interface are described in this paper. Capabilities The WebSpectra site was designed to be a convenient resource for students to practice and develop their spectral problem solving skills. Therefore, the main component of the home page is a list of links to individual spectral problems. In addition to these links, though, WebSpectra provides online instructional documents where students can learn or review basic NMR concepts including chemical shifts, splitting patterns (5), integration, and solvent effects; and IR concepts such as functional group absorptions, hydrogen bonding, and mass effects. There is a search engine that enables students to locate specific types of compounds on the basis of name, formula, or functional group. This can be an important feature, since most textbooks on organic chemistry present the field using a functional-group approach. Related to this is another instructional tool on the home page called WebSpectra IR Comparison. This feature provides the over118
lay of two IR spectra to allow direct comparison of spectral signals based on functional group (Fig. 1). Finally, there are links to other WWW sites that provide information on NMR or IR spectroscopy (6 ). An individual problem page displays the molecular formula for the unknown, the solvent used for the NMR spectra, a list of links to the spectra available for that problem, and a link to the answer. Regarding the last item, the site was constructed with the aim of its being a database of problems for students to learn about spectroscopy and not a testing site. To avoid nomenclature problems for the student, the answer page displays both the IUPAC chemical name and a structural drawing. Following a link to a spectrum, students are presented with a high-resolution spectrum of the unknown compound. Dynamic one-dimensional 1H and 13C NMR spectra (Fig. 2) are available for all problems and IR, DEPT NMR (7), and/or COSY NMR (8) spectra (Fig. 3) are available for some problems.2 The dynamic feature refers to the capability of online delivery of spectra with user-defined spectral windows for the NMR spectra. That is, users can request expansions of the spectra based on regions as defined in ppm, or zoom in to a 0.7-ppm window centered about a particular signal. The spectrum display includes a listing of the signal frequencies in both ppm and hertz to allow for the zoom feature and also coupling-constant analysis. When an expansion is presented, the complete spectrum is also presented in the upper right corner of the display to aid analysis. Since more complex problems can involve interpretation of complex coupling patterns, the expansion feature is a critical component. Some of what was just described, such as document display and lists of problem links, is routine for someone versed in HTML3 (9). However, spectral display is another matter and some of the issues are described in this paper. Full technical details employed in the creation of WebSpectra are posted on the WebSpectra site (10). We point this out because others may wish to create their own WWW sites for presentation of a variety of spectral and other data for educational or research uses. The Display Problem Given the digital nature of modern spectroscopic data, it would seem obvious to use the WWW to present this information. However, while posting of documents and most graphics on the WWW is now routine, presentation of highquality spectral data presents special problems. Principally, the use of the WWW as a distribution medium for spectral data has been hindered by the mutual exclusion of high resolution and format compatibility. Existing spectral Web sites chose to deliver spectra either at lower resolutions (6a), with static magnifications (11, 12), or by providing users with free induction decay (FID) data (13) or proprietary spectral formats (14). While the complex formats deliver high-resolution spectra, they require processing knowledge and programs and this makes them unsuitable for practice spectral problems aimed
Journal of Chemical Education • Vol. 78 No. 1 January 2001 • JChemEd.chem.wisc.edu
Information • Textbooks • Media • Resources
Figure 1. Sample WebSpectra IR comparison spectra.
Figure 2. Sample WebSpectra 1H NMR spectrum.
Figure 3. Sample WebSpectra COSY spectrum.
at undergraduate students. In the WebSpectra site, spectra are presented in the graphic interchange format (GIF), a common format that is directly supported by WWW browsers, while maintaining spectral precision through a dynamic spectrum magnification feature. One important issue is that spectral magnification is principally a one-dimensional function, yet no WWW browser or plug-in supports this type of image manipulation. Dynamic presentation of spectra in the GIF format is made practical through the integration of a common gateway interface (CGI) program and JavaScript into the WWW site. This software addresses two related issues associated with the usage of the GIF image format: size and resolution. The delivery of a complete, high-resolution spectrum in GIF format is generally impractical because the size of the resulting image is unmanageable. On the other hand, presenting a smaller image results in loss of resolution, which may make spectral analysis very difficult. The WebSpectra CGI and JavaScript programs solve the problems of size and resolution by presenting “only what is needed” at any one time. Spectra are displayed at first in a low-resolution image. Students are then given the option to magnify any regions of interest to deliver the high-resolution data. For onedimensional spectra, there are two zoom modes: magnification to a selected region and maximum zoom about a signal of interest. Similarly, in two-dimensional spectra, students are able to choose regions of interest to be magnified. In this way, students may get a general overview of the spectrum before scrutinizing details such as splitting patterns. Implementation Issues The capabilities of the WebSpectra system described above were implemented through initial acquisition and processing of spectral data, and subsequent development of the WebSpectra interface software. The processing of NMR and IR spectra both include graphics format and layout conversions necessary to store the spectra in a format usable by the CGI and for presentation to the user. The WebSpectra CGI is capable of reading, processing, and displaying appropriate information based on the requests of the user as described earlier. JavaScript code is used in combination with CGI to display userrequested regions for subplots. In processing and storing spectra, the need to preserve the high-resolution data brings up immediate problems in the first step of processing: data acquisition. Whereas all IR data were acquired on a Nicolet 510P FT-IR4 and saved as raw XY-plot data, all the proton and carbon NMR spectra on the site were obtained using a Bruker ARX400 spectrometer.5 The acquisition and processing of these spectra, including Fourier transformation (15), phasing, baseline correction, and integration, were performed using Bruker’s proprietary xwinnmr software.6 Details of the subsequent data conversion to a WWW compatible format are available (10).
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The final image format, in which both types of spectra are stored on the WWW server, is a nonstandard, compressed image format designed specifically for WebSpectra. This “WebSpectra format”, designated as the SPC format, was implemented so that access by the CGI program is as fast as possible—about 5 times faster than GIF or uncompressed formats. This is an important point for student use, as slow access times leads to frustration and one problem may require examination and expansions of multiple spectra. Although the processed spectral images are the most important component of the WebSpectra database, there are several auxiliary files that were also generated during data processing to aid student use. These files are in plain text and contain necessary information relating to the corresponding spectra such as compound name and formula, solvent(s) used, and, for 1-D spectra, signal frequencies. These are displayed beside the spectrum and allow calculation of coupling constants as well as location of signals and magnification. The end result of a long series of processing steps is the pages that make up the WebSpectra site (e.g., Figs. 1–3). Although the steps of processing and presentation are complex (10), these go a long way toward making the student user’s life less complex. It is now possible to give students highquality but simple and manageable spectral images that allow them to focus on the most important issue—solving the problems at hand. Results The Web site has been in place since 1996 and has received glowing support from both students and faculty at various levels in the organic chemistry curriculum. Access has been an important feature for users. Being accessible through the Web, it is available without time or location restrictions; and since spectra are displayed in GIF format, they can be viewed by simple browsers without special plug-ins or applets. Clearly, students prefer the free access to the spectral problems to purchasing books, but they also comment on the range of problems and the detail of the spectra. In terms of the allimportant pedagogical impact, it has definitely helped the students who have used the system, but since use has been voluntary to date, an accurate determination of measured improvement is not yet feasible. Finally, not only have students found extra practice material to hone their spectral problem solving abilities, but faculty have integrated this technology into stimulating visual presentations in the classroom. Conclusion WebSpectra has been developed as a powerful resource for delivering NMR and IR spectra online for students to practice their spectral problem solving abilities. Making use of the global Internet, WebSpectra provides students with an accessible learning tool for the study of spectroscopy. WebSpectra opens up new pathways of learning for chemistry students and of teaching for faculty.7 Acknowledgments We thank Jane Strouse, Max Kopelevich, Orville Chapman, and Arlene Russell for helpful discussions. Support from Cambridge Isotope Laboratories is gratefully acknowledged. C.A.M. was a National Science Foundation Young Investigator, 1992–1997 and Camille Dreyfus Teacher-Scholar, 1994– 120
1999. B.C.F. was partially supported by NSF DUE95-55605. Notes 1. WebSpectra can be viewed at http://www.chem.ucla.edu/ webspectra and does not have access restrictions at this time. 2. DEPT stands for Distortionless Enhanced Polarization Transfer. COSY stands for COrrelation SpectroscopY. 3. HTML stands for HyperText Markup Language, which is the file format for a Web page. 4. Nicolet Instruments Corporation. http://www.nicolet.com/. 5. Bruker Instruments. http://www.bruker.com/. 6. xwinnmr, version 1.1; Bruker Instruments Inc., 1997. 7. WebSpectra was awarded a Top 5% Chemistry Site Award in September 1999 (http://www.claessen.net/chemistry/award_en. html) and a StudyWeb Excellence Award in November 1999 (http:// www.studyweb.com/).
Literature Cited 1. This order of topics is not necessarily ideal. See: Chapman, O. L.; Russell, A. A. J. Chem. Educ. 1992, 69, 779. Reeves, P. C.; Chaney, C. P. J. Chem. Educ. 1998, 75, 1006. 2. For a compilation of educational NMR software, see: Lundberg, P. J. Chem. Educ. 1997, 74, 1489. 3. Smith, S. G. J. Chem. Educ. 1998, 75, 1080. Kantardjieff, K. A.; Hardinger, S. A.; Willis, W. V. J. Chem. Educ. 1999, 76, 694. 4. Merlic, C. A.; Walker, M. J. Int. J. Educ. Telecommun. 1997, 3, 261. Glaser; R. E.; Poole, M. J. J. Chem. Educ. 1999, 76, 699. Paulisse, K. W.; Polik, W. F. J. Chem. Educ. 1999, 76, 704. 5. Hoye, T. R.; Hanson, P. R.; Vyvyan, J. R. J. Org. Chem. 1994, 59, 4096. Mann, B. E. J. Chem. Educ. 1995, 72, 614. Thoben, D. A.; Lowry, T. H. J. Chem. Educ. 1997, 74, 68. 6. Two interesting WWW sites retrieve spectra based upon userdefined input data. (a) Hayamizu, K.; Yanagisawa, M.; Yamamoto, O.; Wasada, N.; Horiuchi, Y. Integrated Spectral Data Base System for Organic Compounds; National Institute of Materials and Chemical Research, Japan; http://www.aist.go. jp/RIODB/SDBS/menu-e.html (accessed Sep 2000). (b) Spectroscopic Tools; http://www.chem.uni-potsdam.de/tools/index.html (accessed Sep 2000). 7. Furst, J. E. J. Chem. Educ. 1994, 71, 234. 8. For laboratory experiments using COSY, see: Mills, N. S. J. Chem. Educ. 1996, 73, 1190. Branz, S. E.; Miele, R. G.; Okuda, R. K.; Straus, D. A. J. Chem. Educ. 1995, 72, 659. 9. Hofstetter, F. T. Internet Literacy; McGraw-Hill: New York, 1998. 10. For technical details on the actual processing of data, see: http:// www.chem.ucla.edu/~webspectra/WebSpectra_TD.html (accessed Nov 2000). 11. Van Bramer, S. NMR at Widener University; http://science. widener.edu/svb/nmr/nmr.html (accessed Sep 2000). 12. Smith, B. D.; Boggess, B.; Zajicek, J. Organic Structure Elucidation Workbook; http://www.nd.edu/~smithgrp/structure/ workbook.html (accessed Sep 2000). 13. The FTNMR Free Induction Decay Archive; Department of Chemistry, Pacific Lutheran University: Tacoma, WA; http:// rainier.chem.plu.edu/fid_archive.html (accessed Sep 2000). 14. Dransfeld, A.; Ihlenfeld, W. NMR–SHARC Homepage; http:// www.ccc.uni-erlangen.de/sharc/index.html (accessed Sep 2000). 15. Iannone, M. J. Chem. Educ. 1999, 76, 286.
Journal of Chemical Education • Vol. 78 No. 1 January 2001 • JChemEd.chem.wisc.edu
