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A Literature Exercise Using SciFinder Scholar for the Sophomore-Level Organic Chemistry Course Ian J. Rosenstein Department of Chemistry, Hamilton College, Clinton, NY 13323;
[email protected] The American Chemical Society’s Committee on Professional Training (CPT) has stated in its most recent guidelines for undergraduate professional education in chemistry that students “…must learn how to retrieve specific information from the enormous and rapidly expanding chemical literature” (1). The guidelines also state that “It is essential that students gain experience with online, interactive database searching.” The CPT has allowed for a great deal of latitude in how students are taught about the chemical literature. Surveys of chemistry departments show that some schools choose to teach a formal course in chemical information while others incorporate instruction on the use of the literature throughout the curriculum (2–4). Successful incorporation of chemical information instruction across the curriculum necessitates the availability of appropriate teaching tools, especially for introductory-level courses. Exercises designed to introduce students to Chemical Abstracts have been detailed in the literature (5–7) but reports of exercises using modern online searching techniques are lacking. Several recent articles in this Journal have addressed the use of SciFinder Scholar at the undergraduate level (8–10). However, none of these articles describe a stand-alone introduction to online searching of Chemical Abstracts using SciFinder Scholar. One of the articles discusses the use of SciFinder Scholar in a semester-long course on the chemical literature (8) while the others detail a series of related exercises to be used at the senior undergraduate level (9, 10). This article describes an exercise developed for use in the sophomore organic course that introduces students to the process of searching Chemical Abstracts with SciFinder Scholar using chiral auxiliaries as example compounds.
subject of the exercise is supplemental to, but built upon, what the students are learning in the lecture section of the course. The literature exercise has the following goals: • Acquaint students with the basic principles of searching Chemical Abstracts using SciFinder Scholar. • Expose students to the primary literature to familiarize them with the structure of an original research article and to show them that they are capable of reading and understanding the primary literature. • Introduce the concept of chiral auxiliaries, an important concept in modern organic chemistry that is not usually discussed at the introductory level. • Provide students with an opportunity to work on oral presentation skills.
The exercise is introduced during a one-hour prelab lecture in the 10th week of the second-semester organic course. Each student is given the structure of a compound that has been used as a chiral auxiliary. Examples of a few of the structures are shown in Figure 1; a collection of 24 structures can be found in the Supplemental Material.W The students’ goal for the exercise is to use SciFinder Scholar to do a structure search to find a reference to an article describing a synthesis of their assigned compound and to find a second article, if possible, reporting an application of the compound as a chiral auxiliary. The students present the results of their work to their classmates in a 10–15 minute oral presentation during their lab period in the 14th week of the semester.
The Exercise
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At Hamilton College, students get their first introduction to the chemical literature in the laboratory portion of the two-semester organic chemistry sequence, the second and third courses in our curriculum. They then do more extensive work with the literature in upper-level courses and in their senior thesis research projects. Most of the students’ exposure to the literature in the organic courses involves the use of reference sources containing data on chemical properties and both print and online spectral databases. However, students are also introduced to the primary literature by doing the exercise described in this article. This exercise familiarizes students with the basics of searching for information in Chemical Abstracts using SciFinder Scholar. It is done in conjunction with the laboratory portion of the course; the 652
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CH2O CH3
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H3C
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NH2
CH3
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Ph Ph HO
H Ph
Figure 1. Example of chiral auxiliaries.
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The introductory lecture begins with a brief overview of the concept of chiral auxiliaries. Then, with the use of a computer projection system, the lab instructor demonstrates for the students (a group of 14–18) the SciFinder Scholar search process using a sample compound. The students are shown how to access SciFinder Scholar, enter the structure search mode, draw a compound in SciFinder Scholar, initiate their search, assess the results of their search if multiple compounds are found, access and refine reference information, and read the reference information. Students are then familiarized with the general organization of an article in the primary literature. They are shown a copy of an article reporting the preparation of the sample compound and given an overview of how to find the information they will seek in the articles they find. With this introduction, students are given a handout with instructions on how to use SciFinder Scholar (see the Supplemental MaterialW) and asked to do their searches on their own time over the ensuing three weeks. Hamilton shares a two-user SciFinder Scholar account with two other colleges so students’ access to the database is somewhat limited. To minimize access problems, a maximum of two students are allowed to sign up for each one-hour period during the hours of 8 p.m. until midnight. Students are asked not to log on to SciFinder Scholar during these times if they are not signed up, giving the students signed up the greatest chance of getting access to the system. During any other hour of the day students are free to attempt to log on to SciFinder Scholar as they wish. Forty-five students are able to access the system over a three-week period with no difficulties.
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presentation. Students are told that their goal in making their oral presentation is to teach their classmates about the synthesis and use of their chiral auxiliary. Students are given the option of making their presentation in whatever format they like (PowerPoint, written overheads, chalk talk, etc.) as long as their visual aids are clear. The presentations first describe the synthesis of the chiral auxiliary with a written (or computer drawn) scheme showing the reactions used in the synthesis. Students are told that they do not need to show the mechanisms of all of the reactions but that they should describe in general terms (nucleophilic substitution, aldol condensation, etc.) what types of reactions are being done. They are also told that they should describe in detail the mechanism of any unfamiliar or unusual reactions. Students then describe an example of the use of their compound as a chiral auxiliary. They show a scheme with one or two particularly successful reactions, indicating the yield and stereoselectivity of the reactions. They are again told that they do not need to write out complete mechanisms of familiar reactions but should indicate what type of reaction is occurring. If possible, they should also describe how the chiral auxiliary controls the stereochemistry of the reaction. Students are reminded to include citations on the appropriate slides for the articles from which they have obtained their information. They are given an example of the proper citation format. To help students think about what is important in making an oral presentation, they are given a set of criteria by which their presentations are to be evaluated. These criteria are: • Quality of presentation style
Why Chiral Auxiliaries?
• Organization of presentation
Chiral auxiliaries make an excellent set of compounds for an exercise of this sort for many reasons. First, many chiral auxiliaries have been reported in the literature (11, 12). This makes it easy to find a unique compound for each member of a group of 16–24 students. Second, the syntheses of most chiral auxiliaries are complicated enough that the students have to work a bit to understand them. At the same time, the syntheses usually use fairly standard reaction chemistry so that the students should recognize most of the reactions that they encounter. Finally, chiral auxiliaries are often used to control the stereochemistry of reaction types covered in a standard introductory organic sequence, such as enolate and Diels–Alder reactions. Learning about the use of chiral auxiliaries teaches students about current applications of reactions that they have encountered in their coursework and demonstrates to them that their knowledge has practical applications. Oral Presentations The CPT Guidelines state that “Effective…oral communication skills…are no less essential to the well-trained scientist than to the humanist” (1). The guidelines go on to say that “Frequent exercises in…speaking should be a part of the chemistry curriculum.” This literature exercise gives students a perfect opportunity to practice their critical-speaking skills. Since each student in a lab section is assigned a different compound, each student is able to make a completely different www.JCE.DivCHED.org
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• Quality of visual aids • Thoroughness of information • Explanation of the chemistry
In the instructions for the exercise, specific points to consider are given for each of the criteria (see Supplemental Material).W Student Performance Students have very little trouble finding a list of appropriate references using SciFinder Scholar. The only difficulty that students occasionally encounter is in figuring out how to deal with structure search answer sets with multiple structures. Depending on the number of chiral centers in a molecule, a SciFinder Scholar answer set might contain several specific stereoisomers and also structures with defined relative but not absolute stereochemistry and structures with completely undefined stereochemistry. Students are told that they can find information on either enantiomeric form of their assigned compound but that it is important that they look for the correct diastereomeric form. Once students have a list of potential articles, finding an article with a synthesis and one with an application is the next goal. For compounds whose use has been reported sparingly in the literature, this is a fairly simple matter. For other compounds, however, sorting through a list of a couple hundred references on a popular auxiliary is a challenge. Students
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are advised to look near the chronological beginning of the reference list for a synthesis of their compound since each compound would initially have to be made before it could be used. They are also told to look carefully at titles and to skim through the abstracts for mention of the synthesis of their compound. For finding articles reporting an application of their auxiliary, they are again advised to look carefully at titles and abstracts. The assigned chiral auxiliaries are ones whose syntheses have been reported in the most common journals so availability of journal articles is not an issue. Students’ success in reading and interpreting the articles varies with the complexity of the chemistry reported and with the students’ abilities. Many of the auxiliary syntheses are straightforward, one- or two-step processes utilizing reaction types familiar to the students. A few, however, require many steps and use chemistry that students have yet to encounter. The students, with occasional help, do a good job of interpreting and presenting the syntheses of their auxiliaries. Most students are able to find a second article describing an application of their compound, although for a few seldom-used auxiliaries the article describing the synthesis is also the only accessible article detailing an application. For most auxiliaries, students are able to find an application using a familiar reaction type. Those who cannot usually seek help in understanding the chemistry described and are able to understand and satisfactorily present their findings. Conclusion This exercise provides a directed introduction to the chemical literature for students at an early stage of their undergraduate training. At the same time, it exposes them to an aspect of organic chemistry not typically addressed in an introductory-level course and provides an excellent platform for student oral presentations. While the use of SciFinder
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Scholar is an integral part of this exercise as described here, a similar exercise can be carried out using other online databases or print versions of Chemical Abstracts to achieve many of the same pedagogical goals. W
Supplemental Material
A lab handout for the students, including a step-by-step procedure for carrying out a SciFinder search, and the structures of 24 chiral auxiliaries are available in this issue of JCE Online. Literature Cited 1. American Chemical Society, Committee on Professional Training. Undergraduate Professional Education in Chemistry: Guidelines and Evaluation Procedures; American Chemical Society: Washington, DC, 2003; p 14. 2. Somerville, A. N. J. Chem. Inf. Comput. Sci. 1998, 38, 1024– 30. 3. Lee, W. M.; Wiggins, G. Sci. Technol. Lib. 1997, 16, 31–43. 4. Ricker, A. S.; Thompson, R. Q. J. Chem. Educ. 1999, 76, 1590–1593. 5. Kline, E. A. J. Chem. Inf. Comput. Sci. 1984, 24, 190–192. 6. Epling, G. A.; Franck, R. W. J. Chem. Educ. 1979, 56, 388– 389. 7. Wubbels, G. G. J. Chem. Educ. 1972, 49, 496–497. 8. O’Reilly, S. A.; Wilson, A. M.; Howes, B. J. Chem. Educ. 2002, 79, 524–526. 9. Ridley, D. D. J. Chem. Educ. 2001, 78, 557–558. 10. Ridley, D. D. J. Chem. Educ. 2001, 78, 559–560. 11. Seyden-Penne, J. Chiral Auxiliaries and Ligands in Asymmetric Synthesis; Wiley: New York, 1995. 12. Roos, G. H. Compendium of Chiral Auxiliary Applications; Academic Press: Orlando, FL, 2001.
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