In the Classroom
Organic Chemistry Lab as a Research Experience Thomas R. Ruttledge Department of Chemistry, Earlham College, Richmond, IN 47374
For years, chemists have debated how to make chemistry lab more like a research experience and less like cooking (1). This debate has centered around how to avoid giving students a simple task to complete, giving them instead an experiment to perform. Various proposals have included using problem-solving approaches (2), puzzles (3), and most recently, multitasking (4). While all these methods have benefits, they also all suffer from the fact that every student is doing essentially the same tasks and employing minimal creativity. Little exposure is given to the scientific method and the establishment of proper controls. These methods also suffer from the fact that relatively little, if any, use is made of the product beyond what the traditional synthetic chemist might do and no interdisciplinary work is encouraged. The scientific process depends on creativity and ingenuity. It also depends on the ability of a researcher to use the literature effectively, communicate with
peers, gather procedures for desired tasks and evaluate them, and modify these procedures if necessary for the task at hand. Yet these are exactly the qualities that are lacking from most lab courses. There have been attempts to introduce more ingenuity into labs, but these approaches have not been specifically applied to organic labs (5) or have been applied only to special students (6 ). We decided here at Earlham to take some advice from a group of chemical engineers who advanced the idea for student-designed projects years ago; and we wanted this opportunity to be offered to a greater range of students (7). The method we developed to introduce student creativity and ingenuity into a lab course combines certain aspects of the multitasking approach, because it teaches time- and resource-management techniques, with giving students a real opportunity to design their own experiments. This approach was first attempted in an advanced organic course (spectrosContinued on page 1576
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In the Classroom
copy) and later in our sophomore-level organic laboratory course. The results in both classes were very good indeed, with perhaps the most compelling results coming in the sophomore-level class. The sophomore-level organic class is a fairly typical one at a liberal arts college. The lecture portion of the class contains 70–80 students and the lab class enrolls 40 or so people each semester. The lab class is a two-credit-hour singlesemester course and is offered both semesters; thus most, if not all, of the 70–80 students will enroll in the lab. The lab is designed as a free standing course. Each section will meet twice per week for 3 hours each day. The class typically enrolls slightly more than 50% women (reflective of our college as a whole), predominantly biology majors (both cellular and field biologists). Ot is staffed by one or two professors per semester over the course of the academic year, with daily assistance in the lab of a upper level undergraduate assistant. Description At the beginning of the semester, students are given two sets of experiments to complete. One set, usually consisting of 4–5 experiments (see Table 1 for recent examples), is composed of more routine lab experiments designed to highlight techniques used in organic chemistry (e.g., TLC, meltingpoint determination), reactions studied in class, and, most importantly, any instruments (FTIR, GC–MS, UV–vis, CW NMR) that it will be necessary to become familiar with for the various projects. The second set consists of four broadly defined experiments (Table 1). The only experimental guideline they are given is that they are to attempt to complete each project as efficiently as possible and they must fully characterize all products (including intermediates). The starting materials, pathways, methods, spectral characterizations, etc. are left for the students to discover. The students form lab groups of 2–4, based on their preference, to facilitate peer learning and to enable multiple tasks to be worked on simultaneously. As a source of extra credit points, students are encouraged to show that their product (e.g., DEET or a pharmaceutical), once chemically characterized, is bioactive, with the strict limitation that no human testing be involved. Most groups begin doing the “canned” experiments because these are better mapped out and more familiar. At the same time, they begin using the library for ideas on how to accomplish the other “project-based” experiments, a use of the literature more in keeping with how a typical scientist routinely uses it. We offer extensive bibliographic instruction related to the use of several online databases, including Beilstein, Analytical Abstracts, and Chemical Abstracts. After searching the literature, students often find several procedures for synthesizing the target molecule. This requires that they be able to choose the “best” synthesis, incorporating considerations of cost, safety,
waste disposal, and the level of experimental detail in the journal source. These considerations require that they consult with classmates, the instructor, and other members of the department, and this helps to foster good discussions about chemistry. Progressively, each group chooses a method for each of the student-designed labs. Some (60% or so) modify basic methods in an attempt to improve yield or quality, whereas some (about 40%) simply repeat published methods. We do allow the use of texts containing similar experiments, but the identification requirements at each step add a new level of work to even these approaches. In addition, the extra-credit enticement of demonstrating the utility of the product motivates most of the students (more than 80%) to design these related experiments. With the quality of our library and bibliographic instruction, the vast majority of students use synthetic method monographs or the literature and few use traditional texts. Few, if any, students devise their own syntheses at the sophomore level (students in the advanced organic course do). The groups, all the while, are still doing other experiments and most have begun to divide responsibilities so that they can function more effectively. Productivity in the lab is far higher than with traditional formats—so much so that upper limits must be placed on how much students are allowed to do. The independent syntheses quickly become a passion for most groups. It is a chance to show their stuff and they tend to spend much of their time on them. The students become concerned with product yield and quality, since most have ideas about using the product for the extra-credit demonstration of effectiveness. Some groups do small-scale reactions and then scale up the reaction, much like typical organic chemists. They have ownership of the project and this drives them to succeed at it. A look into how the approaches of students vary in the DEET experiment is instructive. This is the student-designed experiment that is most similar among the groups, as the end target is specified and the literature is readily accessible. The first students to do the experiment generally follow or modify a recent microscale procedure (8). This procedure often presents difficulties in recovery for our students, and the later students often follow or modify an older procedure (9). About onethird of the students make the acid chloride and about twothirds purchase it. We only require that a minimum of one synthetic step occur (with an eye toward safety and cost, of course). The primary modifications a group will make are to molar ratios of starting reagents (after their preliminary reaction shows problems with an unreacted reagent) and to the number and volume of washings and extractions (generally going down in volume and up in number). In a typical section of 7 lab groups, you will see 5 or 6 “different” procedures in
Table 1. Project-Based Organic Laboratory Experiments Pre-planned Experiments
Student-Designed Experiments
TLC of analgesics
Extraction of caffeine from a series of commercial products
Diels-–Alder reaction: reaction of maleic anhydride and cyclobutadiene
Synthesis and characterization of ethyl cinnamate
A puzzle-solving experiment utilizing a Grignard reagent (10 )
Synthesis and characterization of N,N-diethyl-m-toluamide (DEET)
Synthesis of 2'-bromostyrene (11 )
Synthesis and characterization of a pharmaceutical
The addition of HBr to unsymmetrical alkenes (12 )
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use. As an example of the extra-credit projects, one group, who synthesized DEET to high purity (by GC–MS), used two shoe boxes containing lady bugs and covered with clear plastic wrap to demonstrate that DEET does indeed repel ladybugs, although the literature is quiet as to any effects on this species. Another group used fruit flies and a pair of connected bottles (one with DEET, one without). They allowed the flies to “equilibrate” between the two and counted populations. Another example was with the sulfa-based antibiotic, Sulfanilamide. The students, in consultation with a microbiologist in our biology department, designed an experiment to show it inhibited the growth of bacteria on agar plates. Methods The planning for this type of lab is more involved from several standpoints. The instructor must be better organized and be able to give the students all the lab objectives at the beginning of the semester. As I have learned, a well-organized ordering system must be used and it must place the clerical responsibilities of ordering with the students. I have made progress in this area by requiring written proposals for the reactions they are about to attempt, including any literature citations. In addition, all students are given forms to fill out, specifying the quantity on hand of a required chemical (and the current exact location) and what chemicals need to be ordered, with the catalog numbers, cost, and amounts needed, and any hazards of the reagents. We will allow the use of most chemicals that are typically used by undergraduates and where safety is a particular issue, the faculty member will assist them directly in lab with this reagent. Consultation with the students about the proposed method occurs before project approval. A chemical sign-out sheet in the stockroom is mandatory to keep track of chemicals and prevent a free-for-all stockroom attack. Another approach would be to have students requisition supplies from the stockroom. These management techniques, strictly applied, make this type of lab possible. It is critical to impose limits in this type of lab class. Limits that are desirable emphasize materials control (rationing the amount of starting material), and time control (limiting the times when they can be in the lab). Of these, the former is beneficial on its own as it also encourages proper use of other resources and does not penalize students who work more slowly. Grading a course such as this is possible in a variety of ways. We prefer to use formal journal-style laboratory reports from the groups, with a mix from the canned labs and the student-designed experiments. Students are assessed primarily on the quality of their analyses of the data and on the neatness and clarity of the written report. The analyses typically contain the raw visual and physical data during the course of the reactions, all spectral and experimental data relating to the identification of the product(s) (including major side products), and the student’s interpretation of these data. We also expect students to realize weaknesses in their data and suggest ways of improvement if they were to repeat the experiment. We have never graded students on yields or purity here at Earlham, but with the requirement that they identify major side products, there is motivation for them to improve
yields and purity. We also do not directly grade on efficiency, number of steps, or cost, but we work with them before they start to avoid obvious problems in these areas. Conclusion What has happened with this type of lab is significant. Students are given ownership of their projects and are aided in completing them. They start to explore the literature, talk to classmates about chemistry, and involve the faculty from the chemistry department and other departments in their work—and they are excited about lab. They are encouraged to be creative, efficient, and cost-effective, things not often learned in a typical lab setting. They start to really “do” science. Encouraging them to demonstrate the effectiveness of the product requires that they do interdisciplinary work, which is typical of today’s organic chemist and more importantly, tomorrow’s organic chemist. They learn much more in terms of designing experiments and analyzing data, with the possible loss of being exposed to a myriad of organic techniques. The feedback on evaluation forms has been overwhelmingly positive; most students advocate getting rid of the “canned” experiments completely. This does not seem advantageous at this point because of the exposure to instrumentation that these labs give, as well as their being a place to start. Although this type of lab will not be enormously different from the typical lab for weaker students, it offers a degree of challenge and a chance to personalize experiments for the stronger students, who are the students that rate the typical lab experience as dull. I can say as an instructor that I have been amazed and excited by the experiments they have planned, and that has not happened often in a laboratory class. Any further skepticism should be discarded when it is noted that two students here have developed independent research projects based on “their” projects. When is the last time this happened in a traditional lab? Acknowledgments I am indebted to my colleagues here at Earlham, whose constant search for better ways to teach chemistry inspired me to undertake this change. I am also indebted to the students whose willingness to try new ideas made this possible. Literature Cited 1. Venkatachelam, C.; Rudolph, R.W. J. Chem. Educ. 1974, 51, 479–482. 2. Wilson, H. J. Chem. Educ. 1987, 64, 895–896. 3. Pickering, M. J. Chem. Educ. 1991, 68, 232–234. 4. Alty, L. T. J. Chem. Educ. 1993, 70, 663–665. 5. Dutzler, M. A.; Ricci, R.W. J. Chem. Educ. 1994, 71, 685–688. 6. Wilson, L. R. J. Chem. Educ. 1969, 46, 447–450. 7. Macias-Machin, A.; Zhang, G.; Levenspiel, O. Chem. Eng. Educ. 1990, 78–79, 116. 8. LeFevre, J. W. J. Chem. Educ. 1990, 67, A278–A279. 9. Wang, B. J.-S. J. Chem. Educ. 1974, 51, 631. 10. Silversmith, E. F. J. Chem. Educ. 1991, 68, 688–690. 11. Corvari, L.; McKee, J. R.; Zanger, M. J. Chem. Educ. 1991, 68, 161–162. 12. Brown, T. M.; Dronsfield, A. T.; Ellis, R. J. Chem. Educ. 1990, 67, 518.
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