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Exploring Chemistry Resources on the Internet Steven Murov Science, Mathematics and Engineering Division, Modesto Junior College, Modesto, CA 95350;
[email protected] The Internet has rapidly emerged as an important resource of chemistry information (1). Discovering the scope of information available and how to find it should be a part of the undergraduate education of every chemistry student (2). In today’s high tech society, Internet connections are often more readily available than chemistry reference books. In addition, Internet sites have information (such as collections of spectra and LD50 values) that is often not available in high school and community college libraries. The purpose of this article is to suggest some possible introductory Internet experiences and to present a few search challenges that use important chemistry sites on the Internet. There are several methods of searching for desired chemistryrelated information, including general and specific search engines (3), chemistry directories (4 ), and chemistry keyword search sites (see ref 4 for links). For a chemistry student, arguably the six most valuable chemistry sites on the Internet are Mark Winters’s WebElements (5), a periodic table with a plethora of information about elements; ChemFinder Web Server (6 ), ChemExper Chemical Directory (7), and ChemQuik (8) sites for properties of substances; the NIMC (National Institute of Materials and Chemical Research, Japan) Integrated Spectral Data Base System for Organic Compounds collection of IR, NMR, and mass spectra (9); and the NIST (National Institute of Standards and Technology) collection of gas-phase infrared spectra, mass spectra, and thermodynamic data (10).
This search reveals that meteorites have about 1000 times more iridium than the earth’s crustal rocks. This observation led a Berkeley team consisting of geologist Walter Alvarez, his late father, physicist and Nobelist Luis Alvarez, Frank Asaro, and Helen Michel to suggest that the high iridium content in a very thin layer in the earth’s crust was caused by a disastrous meteor impact. The postulated impact may have been responsible for the extinction of many life forms and some researchers have attributed dinosaur extinction to the event (11). To supplement this search, search engines can be used to find biographical information on the discovery team. There are also at least two sites dedicated to information about Nobel Prize winners (12). Sites that discuss the extinction event are also plentiful (suggest searches for extinction, 65 million, asteroid impact, iridium layer, etc.). WebElements can be used to search for interesting extremes of properties—for example, to find six stable elements with the highest melting point, density, mineralogical hardness, or superconductivity temperature. Searches can also be performed for elements that have desirable properties for items such as pots and pans, jewelry, or hammer heads. It should be pointed out to students that using WebElements limits the desirable properties search to elements, even though alloys should also be considered. Despite this weakness, the search does require the student to think about what kinds of properties (e.g., density, strength, hardness, cost) would be best for the application.
Properties of Elements and Isotopes
Properties and Hazards of Compounds
Of the many periodic table sites, WebElements (5) has the most information and is one of only a very few that contain graphs of periodic properties. Students can be asked to search for physical, chemical, and nuclear properties, uses, abundance, and history of the elements. When covering atomic masses and isotopes early in chemistry courses, it is common practice to demonstrate how the atomic masses in the periodic table can be obtained from mass spectrometric data. Using WebElements under “Nuclear Properties” and “Naturally Occurring Isotopes”, students can be asked to calculate the average atomic mass of an element from isotopic abundances and masses. Elements such as chlorine, bromine, and copper are ideally suited for this calculation. For instructors who want students to use mass spectra that are probably closer to the originals, the NIST site (10) includes expandable mass spectra of argon, krypton, and xenon. It is possible to do approximate calculations using whole-number isotopic masses on argon, krypton, and xenon directly with the site, and improved calculations can be made by using the isotopic masses to four places after the decimal from a source such as WebElements (5). One interesting search using WebElements (select the professional edition, WebElements Pro) pertains to the asteroid impact with the earth 65,000,000 years ago. Students can be asked to search for the abundance of iridium (under its geology heading) in the earth’s crustal rocks and in meteorites.
The Internet is also a very good resource for properties of compounds. Material Safety Data Sheets are numerous and generally easy to find. Physical properties are included in addition to the important safety and hazard information in the MSDSs. Chemfinder Web Server (6 ) has indexed links to information available on compounds. ChemExper Chemical Directory (7), ChemQuik (8), Vermont Safety Information Resources (13), Cornell University (14), and MSDSSearch (15) are among the other sites that quickly lead to the desired information. Usually included in the MSDSs are LD50 values, an important property that probably deserves more discussion in chemistry courses. Many interesting searches for properties and LD50 values can be assigned to students. One very sad but true example involves caffeine. Students can be asked to find the oral rat LD50 value for caffeine (192 mg/kg) (7) and to estimate the amount of caffeine needed to kill half the number of 65-kg people who consume this amount (12.5 g). It is probably valuable to discuss the assumptions and issues involved in making this estimate, such as species differences in metabolism and the argument that extrapolation from rats to humans should be based on surface area ratios rather than weight ratios.) From this number, assuming that there is 100 mg of caffeine in a cup of coffee, the number of cups of coffee that are potentially fatal can be calculated (125 cups). Now stu-
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dents can be told to read a paper (16 ) where they will find that a student on a dare took pills totaling 25 g of caffeine and died. While the calculations are crude, the reality of this story should deliver the lesson. Other LD50 searches of interest include a comparison of the values for ethylene glycol and propylene glycol, and noting the very low value for vitamin B12 and the low value for barium ion (even though barium sulfate “milk shakes” are administered prior to a series of gastrointestinal X-rays without lethal results). The NIST site (10) can be used to obtain data for Hess’s law calculations. For example, students can find the heat of formation of water and carbon dioxide as well as the heat of formation and combustion for methane (g), ethane (g), propane (g), and 2,2,4-trimethylpentane (ᐉ). Then the heat of formation can be used to calculate the heat of combustion (using Hess’s law) for hydrogen, methane, ethane, propane, and 2,2,4-trimethylpentane (ᐉ) and the heat of vaporization of water. The calculated values can be compared to the already located heats of combustion at the NIST site (10). The students should then be asked which of the hydrocarbons is the best source for heat and how it compares to hydrogen. Applied Chemistry The current controversy regarding the use of methyl tertbutyl ether (MTBE) is another good topic for a search. Students can be directed to the Chemical and Engineering News article (17) posted on the Web that shows the sharp increase in use of MTBE through 1996. Students can be asked to search for the reasons MTBE was put into use and why it is being phased out. This should make an interesting class discussion. Students can be asked to find the rather surprisingly high solubility of MTBE (5.1 g/100 mL) (6 ) in water, which is one of the reasons it is a threat to drinking supplies. However, its LD50 value (4g/kg) (18) does not seem to make MTBE a toxic threat. An inspection of chlorofluorocarbon production as a function of year in the same article can lead to a beneficial discussion of the ozone hole. Some fascinating history is revealed by the site called Nitrogen: Food or Flames (19). The site reveals a huge shift in the source of nitrogen for fertilizer between the years 1913 and 1934. Students can be referred to the site and asked to comment on the impact of chemistry on fertilizer production. Until shortly after 1913, bird guano from Chile was the world’s major source of fixed nitrogen. However, Fritz Haber’s development of ammonia production from nitrogen and hydrogen in 1908 led to a change. The need for nitrogen explosives during World War I led to construction of plants that used the Haber–Bosch ammonia synthesis, and the primary source of nitrogen changed from guano from Chile to industrial plants. It is also worthwhile to have students find out more about Haber at one of the Nobelist information sites (12) or by using a general search engine. Significant Figures and Unit Conversions It is often hard to convince students of the importance of significant figures and unit conversions. Real-world examples help to persuade students that these concepts and tools need to be mastered. A couple of classic papers by Rayleigh are available on the Internet and provide a meaningful reading 1430
adventure (20). Students can be asked to record Rayleigh’s measurements to three and five significant figures for the mass of “nitrogen” in a flask generated chemically and obtained by removal of the oxygen from the air. The values agree to three significant figures but are clearly different to five significant figures. This alert observation by Rayleigh led to the discovery of argon by Rayleigh and Ramsay. This event can also be used as an example of the importance of not overlooking even small differences in results (21). For those who want a more in-depth analysis of the Rayleigh discovery, it is possible to calculate the atomic mass of argon rather accurately from his nitrogen data and the abundances of nitrogen and argon in the atmosphere (available at WebElements [5] or more accurately at a meteorology site [22]). Another true story illustrates the significance of units and unit conversions. In 1983, an incorrect assignment of units to the density of gasoline caused Flight 143, bound from Montreal to Edmonton, to run out of gas (23). Fortunately the plane was able to make a safe emergency landing on an abandoned landing strip near Winnipeg. Students can be given the unit conversion with the incorrect and correct units along with the amount of fuel in the tank and the amount needed for the flight. They can calculate the shortage and understand why the plane ran out of fuel (exercises on this event are available in print [24] and on the Internet [25]). This experience should help develop an appreciation for the importance of units and unit conversions. Another true story about a unit mistake that led to a demoralizing time and financial loss involved a Mars lander that disappeared (26 ). Organic Spectroscopy For organic chemistry courses, one of the most important resources on the Internet is the large NIMC collection (9) of NMR, IR, and mass spectra. The NIST site (10) also contains a sizeable collection of IR spectra, but the spectra were run in the gas phase and the noticeable differences between solutionand gas-phase spectra can confuse students. The NIST site does contain an excellent library of expandable mass spectra. ChemExper contains 5000 useful IR spectra (7 ) and with Organic Compounds Data Base (27), NIMC (9) and Galactic (28) can assist with the identification of organic compounds from physical and spectroscopic data. To a limited extent, these sites can also help with the selection of materials with desired properties. While it is best to use the four sites above with data students obtain from unknowns, practice assignments can be given to familiarize students with the sites. For example, if a student is told that a compound has a refractive index of 1.526 ± 0.01, a boiling point of 218 ± 5 °C, and an IR absorption at 1690 ± 10 cm᎑1 as well as aromaticity absorptions, ChemExper (7) will provide a list of possible hits including 3-acetylpyridine, 2-methylacetophenone, methylsalicylate, propiophenone, and butyrophenone. Given the same information, the Organic Compounds Data Base (27) suggests propiophenone, 2-methylacetophenone, and 3-methylacetophenone. The data base of ChemExper (7 ) includes 3-methylacetophenone but the search does not locate it apparently because its refractive index is not included in the data base. Students need to be alerted to this potential problem. (As of this writing, the ChemExper instructions [7] would lead you to believe
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that it will accept NMR data. However, it does not currently have an NMR data base and NMR data should not be entered or no hits will result). The Organic Compounds Data Base (27) has a limited selection of compounds and obviously does not find compounds that are not included. With ChemExper (7), students can instantly check for an IR match if they have obtained or been provided with the IR. Otherwise, they can now be asked what information they need to eliminate possibilities, recognizing that the correct result may not be included in either data base. If NMR information is available, students should be able to analyze for consistency with the structures and they can check the NIMC (9) site for a possible match. Societal Issues and Biographical Searches Other possible Internet assignments include the use of search engines to find out more about societal issues such as the greenhouse effect, the ozone hole, nuclear fission, radon in homes, fluoridation of public water supplies, and nitrites. Biographical searches on people such as Karl Ziegler, Wallace Carothers, Carl Djerassi, Rosalind Franklin, Fritz Haber, Lise Meitner, and Stanley Pons can lead to provocative class discussions. Students might find glossaries of chemical terms to be handy (29). Other sites that might be worth a visit include a safety exercise (30) and chemical puns (31). The Internet is also an excellent source for tutorials on many chemistry topics. Students having difficulty with a topic might find one of the different approaches available in a tutorial helpful. Bob Jacobs maintains an up-to-date directory of tutorials on the Internet (32). Finally, the computer is at last coming of age by taking advantage of its interactive capability. One example is the set of exercises written for preparative and general chemistry level that is available on the Wiley server (33). Included among the multiple-choice questions with instant feedback are many conceptual questions. Conclusion The Internet is a valuable resource for many kinds of chemical information. There is no doubt that the amount of information available will continue to grow rapidly. Use of the Internet can save considerable library research time, yet students should be made aware that the authenticity of information on the Internet is not guaranteed and sites change addresses and sometimes even disappear. In addition, it is very important that original sources be consulted and cited in research papers. Despite these limitations, the Internet provides users with a very accessible and rapidly growing chemistry reference library. Literature Cited 1. For continuing articles on WWW sites, see articles in J. Chem. Educ. by C. S. Judd, J. L. Holmes, D. J. Wink; in Chem 13 News by E. Doadt; and in Educ. Chem. by P. Collie. 2. McGowan, C.; Sendall, P. J. Chem. Educ. 1997, 74, 391. Stevens, K. E.; Stevens, R. E. J. Chem. Educ. 1996, 73, 923. Mounts, R. D. J. Chem. Educ. 1996, 73, 68–71. Tissue, B. M. J. Chem. Educ. 1996, 73, 65–68. Holmes, C. O.; Warden, J. T.
J. Chem. Educ. 1996, 73, 325. 3. For links to and discussions of general and topic specific search engines, visit: http://www.zdnet.com/searchiq/; http://www. searchengineshowdown.com/; http://nuevaschool.org/~debbie/ library/research/adviceengine.html; http://www.searchengines.com; http://searchenginewatch.com/; http://websearch.about.com/ internet/websearch/; http://dir.yahoo.com/computers_and_internet/ internet/world_wide_web/searching_the_web/search_engines/ index.html (all accessed Jul 2001). 4. For example, visit the Chemistry Webercises Directory and the list of directories contained therein; http://www.wiley.com/ college/webercises (accessed Jul 2001). 5. Winter, M. WebElements; http://www.webelements.com/ (accessed Jul 2001). 6. ChemFinder; http://www.chemfinder.com/ (accessed Jul 2001). 7. ChemExper Chemical Directory; http://www.chemexper.com/ccd/ power/index.shtml (accessed Jul 2001). 8. MSDS Public Service Library. ChemQuik; http://www4. chemquik.com/scripts/main.asp (accessed Jul 2001). 9. Hayamizu, K.; Yanagisawa, M.; Yamamoto, O.; Wasada, N.; Someno, K.; Tanabe, K.; Tamura, T.; Hiraishi, J. Integrated Spectral Data Base System for Organic Compounds (SDBS); http://www.aist.go.jp/RIODB/SDBS/menu-e.html (accessed Jul 2001). 10. NIST. Chemistry WebBook; http://webbook.nist.gov/chemistry/ (accessed Jul 2001). 11. See for example: Lingham-Soliar, T. Sci. Spectra 1999, No. 17; http://www.gbhap.com/Science_Spectra/17-article.htm (accessed Jul 2001). 12. Nobel Foundation; http://www.nobel.se/index.html. Nobel Prize Internet Archive; http://www.almaz.com/ (both accessed Jul 2001). 13. Vermont Safety Information Resources, Inc. (SIRI); http:// hazard.com/msds/index.html (accessed Jul 2001). 14. Cornell University Material Safety Data Sheets; http:// msds.pdc.cornell.edu/msdssrch.asp (accessed Jul 2001). 15. MSDS-Search; http://www.msdssearch.com/ (accessed Jul 2001). 16. Rosin, J. Caffeine Pills Can Have Fatal Effects; Dailey Free Press; http://www.dfpress.com/media/paper87/DFPArchive/science/ 1103981.html (accessed Jul 2001). 17. Production in the U.S. Chemical Industry; Chem. Eng. News 1996, 74 (Jun 24); http://pubs.acs.org/hotartcl/cenear/960624/ prod.html (accessed Jul 2001). 18. Mallinckrodt Baker. Methyl tert-Butyl Ether MSDS; http:// www.jtbaker.com/msds/b7222.htm (accessed Jul 2001). 19. Pafko, W. Nitrogen: Food or Flames; http://www3.cems.umn.edu/ orgs/aiche/archive/history/h_s_n2.html or http://www.che.boun. edu.tr/~che/akman/history/h_s_n2.html (accessed Jul 2001). 20. Giunta, C. J. Classic Chemistry; http://webserver.lemoyne.edu/ faculty/giunta/rayleigh0.html or http://webserver.lemoyne. edu/faculty/giunta/rayleigh.html (accessed Jul 2001). 21. Giunta, C. J. The Discovery of Argon: A Case Study in Scientific Method; http://webserver.lemoyne.edu/faculty/giunta/acspaper.html (accessed Jul 2001). 22. Pidwirny, M. J. Fundamentals of Physical Geography; Chapter 7; http://www.geog.ouc.bc.ca/physgeog/contents/7a.html (accessed Jul 2001). 23. Hoffer, W.; Mona, M. Freefall; St. Martin’s: New York, 1989. Banks, P. ChemMatters 1996, 14 (4),12–15. 24. Murov, S.; Stedjee, B. Experiments and Exercises in Basic Chemistry, 5th ed.; Wiley, New York, 2000.
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Information • Textbooks • Media • Resources 25. Banks, P. The Crash of Flight 143; American Chemical Society ChemCenter; http://www.acs.org/vc2/2my/my2_143.html. Chemical Engineers Resource Page; http://www.cheresources. com/flightzz.shtml (both accessed Jul 2001). 26. For example, see: CANOE (Canada’s Internet Network); http:// clive.canoe.ca/CNEWSHeyMartha9911/10_metric.html (accessed Jul 2001). 27. Bell, H. M. Organic Compounds Data Base; http://www.colby. edu/chemistry/cmp/cmp.html (accessed Jul 2001). 28. ThermoGalactic Spectra Online; http://spectra.galactic.com/ spconline/ (accessed Jul 2001). 29. Jacobs, B. Relevant (High School) Chemistry Resources on the Web; http://www.chemistrycoach.com/high.htm#definitions of chemical (accessed Jul 2001). All of the following: http://antoine. frostburg.edu/chem/senese/101/glossary.shtml; http://www.chem.qmw.
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30. 31. 32. 33.
ac.uk/iupac/; http://netaccess.on.ca/~dbc/cic_hamilton/dictionary/ a.html; http://www.harcourt.com/dictionary/; http://www. treasure-troves.com/chem/, http://www.chem.vt.edu/chem-ed/ scidex.html; http://www.wbaileynet.com/wldchem/home/refer/ aframe.htm, http://www.infoplease.com/; http://klbproductions. com/yogi/chemistry/dictionary/ (all accessed Jul 2001). Murov, S. The Chemistry Laboratory: A Lesson in Safety; http:// virtual.yosemite.cc.ca.us/smurov/remsen.htm (accessed Jul 2001). Murov, S. Chemical Puns; http://virtual.yosemite.cc.ca.us/smurov/ chempuns.htm (accessed Jul 2001). Jacobs, B. Tutorials; http://www.chemistrycoach.com/ tutorial.htm#tutorials (accessed Jul 2001). Murov, S. Supplementary exercises for Malone, L. J. Basic Concepts of Chemistry; http://college.wiley.com/Malone322474/ resources/malone_site/Malone.htm (accessed Jul 2001).
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