In the Laboratory
On the Successful Use of Inquiry-Driven Experiments in the Organic Chemistry Laboratory Jerry R. Mohrig* Department of Chemistry, Carleton College, Northfield, MN 55057; *
[email protected] Christina Noring Hammond Department of Chemistry, Vassar College, Poughkeepsie, NY 12604 David A. Colby Department of Chemistry, University of California at Irvine, Irvine, CA 92697
The 2004 Commentary article published in this Journal by one of us (JRM) set forth the sterile nature of organic chemistry laboratory courses that utilize cookbook verification experiments (1). Although that paper discussed the problems with this type of teaching, it did not attempt to consider the possible solutions in any detail, beyond indicating the importance of question-driven, guided-inquiry experiments. A more thorough treatment of what can work to enliven the modern organic teaching laboratory in a variety of educational environments is the purpose of this article. Nomenclature Although Domin has proposed a taxonomy of laboratory instructional styles for inquiry-driven laboratory teaching (2), different authors use the same terms in different ways. Thus, it is helpful to consider the terms we will use in this article. Inquiry-driven experiments for the organic laboratory can be divided into three categories: (i) guided-inquiry experiments; (ii) design-based experiments; and (iii) open-ended inquiry experiments. Each of these teaching approaches allows students to participate in the process of science, in contrast to the experience of students enrolled in typical courses that use the verification approach. In inquiry-driven lab work students have the opportunity to think as they perform their experiments and as they draw conclusions from their results. Guided-inquiry or discovery experiments have been proposed by many chemists (1–7). Guided-inquiry experiments may or may not provide detailed experimental procedures, although they always pose questions worthy of investigation, which students answer by analyzing their experimental results. In designed-based and open-ended inquiry experiments students are asked to design their own procedures. Open-ended inquiry experiments are more ambitious, with students using primary and secondary chemical literature sources to find possible models that they can adapt, with faculty consultation, for their experimental work. Design-based experiments are used most often in the context of synthetic chemistry, where students adapt generic procedures in order to synthesize specific target compounds or carry out specific reactions. Using a mix of guided-inquiry and design-based experiments is feasible to do in introductory organic chemistry lab courses. This approach can provide students with experience in two of the most important parts of experimental chemistry—the significance and careful analysis of experimental data and the design of experiments. Both engage students in thinking about how to do experimental science. 992
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One example of the lack of a standard nomenclature is the term project. We suggest that project doesn’t have to imply any particular type of pedagogy. A project can simply refer to a series of related experiments that are carried out over 2–4 weeks’ duration. The use of multi-week related experiments has many advantages both when students are provided with experimental procedures and when they design their own procedures. Projects can be based on the guided-inquiry or discovery approach, on traditional multi-step organic syntheses, on design-based experiments, or on open-ended inquiry experiments. The traditional approach of having students complete a separate experiment each week is a straightjacket that often impedes effective learning. Multi-week sets of related experiments allow students to take more ownership of their lab work and become more engaged and self-regulating in their learning. In addition, multi-week projects have a flexibility that lets students repeat procedures successfully if they have made mistakes, a potent educational experience. This flexibility also allows for important post-laboratory discussions of student results and their interpretations. Examples of Guided-Inquiry Experiments In the past, qualitative organic analysis provided guidedinquiry lab teaching. It was always popular and was a good learning experience. Why did it work so well? A student experienced the process of science by deciding which classification tests would be helpful in solving the puzzle, thinking how to adapt them to particular compounds, and finally interpreting the evidence to find a compound’s structure. But organic chemists don’t use qualitative chemical tests anymore in determining the structures of compounds. We use modern spectroscopic methods—NMR, IR, and MS. Teaching the out-of-date techniques of “qual organic” becomes increasingly difficult to justify. Solving the structures of unknowns with modern spectroscopy alone removes much of the intrinsic pedagogical value of interpreting experimental results from chemical reactions. What we need are laboratory experiments and projects that provide the same kinds of experiences for our students as “qual organic” once did, yet in a modern setting. The following two examples may make it clearer what we mean by guided-inquiry experiments. They come from two published organic chemistry lab manuals that feature guided-inquiry or problem-solving experiments (8, 9). These examples ask students to use their previous experience to predict the outcome of an experiment and, after carrying out
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their laboratory work, to interpret their experimental results to answer the question posed. You will notice that the techniques of organic chemistry are imbedded in the experiments.
E2 Dehydrobromination of 2-Bromoheptane The question in this example concerns the effect that the bulkiness of the base has on the product composition in the E2 dehydrobromination of 2-bromoheptane (8). Before experimental work begins, students use their understanding of E2 reactions to predict the product composition, where product stabilities, as well as steric factors, need to be considered. After running the reaction, they use GC to separate
the products and determine their distribution. Finally, the students interpret their experimental results. This one-lab period experiment works well with a two-student team, each student studying one of the alkoxide bases. If a programmable GC is used for the product analysis, a peak for 2-methoxyheptane can also be observed, providing the opportunity for discussing competition of E2 and SN2 pathways. (See Figure 1.)
Reacting Iodoethane with Sodium Saccharin In this lab students experiment to find what product is formed in the reaction of iodoethane with sodium saccharin (9). (See Figure 2.) The conjugate base of saccharin is an
Figure 1. The E2 product mixture in a guided-inquiry experiment reacting 2-bromoheptane with a base.
Figure 2. Possible products in a guided-inquiry SN2 reaction of sodium saccharin.
Figure 3. Possible products in a guidedinquiry experiment on the diacetylation of ferrocene.
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ambident anion, with charge delocalized over the nitrogen and oxygen atoms of the amide functional group. Therefore, either the nitrogen or oxygen atom can be the nucleophile in the SN2 reaction. NMR chemical shift and integration data or HPLC analysis can be used to determine the product composition. Change of the cation from sodium to potassium is reported to produce a substantial change in the composition of the product mixture (10). Recasting Conventional Experiments How does one recast a traditional verification experiment into a guided-inquiry or design-based project that gives students the opportunity to become actively engaged in scientific problem solving? The following two examples illustrate the general approach.
Diacetylation of Ferrocene The acetylation of ferrocene is a popular experiment that demonstrates electrophilic aromatic substitution and has brightly colored substrates and products. It provides an excellent opportunity to introduce students to the techniques of liquid chromatography and thin-layer chromatography. Especially appealing is the fact that the progress of the chromatograms can be followed visually. Recasting the experiment as the diacetylation of ferrocene produces a guided-inquiry experiment with an interesting question, in which students can use their knowledge of electronic effects in electrophilic aromatic substitution to predict the product(s) of the reaction (8). (See Figure 3.) The identity of the major diacetyl product is relatively straightforward to predict using a basic understanding of the relationship of electronic effects and the rate of electrophilic substitution. At least, it is straightforward if biphenyl is the substrate. Do the same rules apply to ferrocene? Students can find the answer from their experimental data. In addition, there is a minor product whose identity is much more difficult to predict. Liquid chromatography provides an easy separation of the mixture of acetylation products, and their identity can be determined by NMR spectroscopy or melting points. An interesting aspect of this two-week project is that, even with the power of modern chemical theory, it is not at all straightforward to rationalize why one possible minor product forms rather than the other. Students come to realize that organic chemistry is not a closed book, that challenges remain.
Figure 4. A traditional Grignard project.
Grignard Synthesis as a Design-Based Project Grignard chemistry is the traditional example of using an organometallic reagent in organic synthesis and is typically encountered as a verification lab experiment. One common variation is combining Grignard methodology with an SN2 synthesis of a bromoalkane, thereby creating a 2–3 week project. (See Figure 4.) A conventional multi-step synthesis may be difficult to recast into a question-driven, guided-inquiry experiment, yet it is relatively easy to recast into a design-based project where students have the opportunity to adapt generic procedures to synthesize specific target compounds. This type of synthesis project is particularly effective when robust reactions, such as SN2 and Grignard reactions, are used. (See Figure 5.)
Figure 5. A design-based Grignard project.
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A generic procedure for this project could lead to 24 possible products. Students look up the properties of their particular substrates and then design procedures for their reactions. The four primary alcohols react at similar rates in the acid-catalyzed SN2 reaction, and rearrangement is not a major problem. Aldehydes and ketones react at substantially different rates that must be controlled by the rate of addition of the carbonyl substrate to the stirred Grignard solution. After the synthesis is complete, a student purifies the final product and determines its structure using a variety of physical and spectroscopic techniques. One could challenge stronger students by using a generic procedure at one scale and suggest that the reactions be done on a different scale. Implementation and Type of Institution Before we discuss implementation strategies for inquirydriven experiments and projects, it is worthwhile to consider the spectrum of colleges and universities where organic lab instruction takes place. There are four broad groups of institutions—research universities, comprehensive universities, small four-year colleges, and two-year community colleges. These groups often have very different environments, and their challenges in implementing guided-inquiry and designbased experiments may be quite different. Some experiments will undoubtedly work better at some institutions than at others: the best choices will depend on local factors. Our experience derives mainly from using this teaching approach at four-year, liberal arts colleges, where we have used guidedinquiry experiments for a number of years. They have been popular with our students and have provided effective student learning. We believe that the active learning inherent in inquiry-driven laboratory instruction will provide significant benefits across the board if it is implemented with thoughtfulness and care. The chemical education literature offers some support for this position (3, 11–14).1 In 2005 we organized a workshop—hosted by the University of California at Irvine and sponsored by the Center for Workshops in the Chemical Sciences (CWCS) (15)—that brought together a diverse group of 20 organic chemists from research universities, comprehensive universities, four-year liberal arts colleges, and community colleges. The workshop considered the value of inquiry-driven experiments, while also considering potential difficulties in implementing this style of lab teaching in a variety of educational environments. The workshop purposely employed graduate-student teaching assistants (TAs), one of whom is a coauthor of this article. The ideas on implementing inquiry-driven organic chemistry lab courses are ours; however, we are indebted to the workshop participants for effective discussions of the issues involved. We especially thank Angelica Stacy for presenting her findings on supporting TAs in the enactment of guided-inquiry. Implementing an Inquiry-Driven Organic Laboratory Two important questions should be addressed when considering any proposed instructional change: • Will the new program serve our students better than what we are currently doing? • How can we effectively implement the new program?
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Even if you are dissatisfied with the current situation, new ideas actually have to work in your local environment. Some teaching approaches, though very appealing, may not work in your teaching environment. A number of years ago one of us attended a management workshop where the instructor told a memorable story. Although one needs to treat with care the applicability of business models to education, this story seems directly applicable to changing a laboratory program. If you are considering changes in your program and have three options, the instructor asked, which would you choose? 1. Changes that will disrupt your program very little and will have a high probability of success. If they succeed, they will have little impact on the effectiveness of your program. 2. Changes that may cause short-term disruption, will involve new ways of doing things, and will have a fair chance of success. If they succeed, they will bring about substantial benefits to your program. 3. Changes that will almost bring your program to a stop while they are being brought about and are highly unlikely to succeed. If they do succeed, they will revolutionize your program.
The answer was option 2. Why bother with option 1, which won’t make any difference when it works? If option 3 fails, as is likely, many people will be highly displeased at the massive disruption for no apparent gain. Option 2 can clearly be worth the gamble and is likely to have substantial educational benefits. Moving toward a guided-inquiry and designdriven laboratory program is a feasible reform in the option 2 category. A number of factors affect implementation of inquirydriven experiments in an organic chemistry lab program: • Conveying the goals and methods to all concerned • Positive faculty participation • Appropriate TA training • Providing time for pre- and post-lab discussions • Availability of modern instrumentation • Availability of suitable written background materials
These factors play out differently in research universities, comprehensive universities, four-year colleges, and community colleges. Thus we have a matrix of six important factors that will affect success and four different types of environments, with a spectrum of diversity within each one. Naturally, the specific approach has to be compatible with the local environment. Conveying the Goals and Methods to All Concerned Once you have decided to adopt an inquiry-driven approach to organic chemistry laboratory teaching, the first important factor in its implementation is explaining to everyone why the change is being made, so that they can join in favoring the reforms. “Everyone” includes the faculty, the
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laboratory director, graduate and undergraduate student TAs, and the students. Communicating effectively with the students why the rules have changed is crucial (16). They may only be familiar with the conventional verification approach and assume that the lab work in the organic chemistry course will be similar. Discussing the purpose and benefits of guided-inquiry or design-based labs makes a great topic for an opening lab lecture. It would also be useful for the faculty member who is teaching in the classroom to take a few minutes in an initial lecture to explain the goals of both the classroom and laboratory parts of organic chemistry and how the two parts fit together. Students need to know what to expect and what they will gain by doing these kinds of experiments. They will develop scientific critical-thinking skills and learn much more from their laboratory experiences. Students will have to do more thinking in the lab, and initially at least they will see this as more work. If the expectations are communicated effectively, most students will have a high probability of success, which will also show them the worth of their additional work. Faculty Participation If the teacher doesn’t care whether the curriculum works, it probably won’t work. If guided-inquiry lab teaching is to be adopted and succeed, the faculty members must care whether the undergraduate students learn effectively from their laboratory experiences. The entire organic chemistry faculty need to buy into the instructional change. Faculty members teaching the organic chemistry courses should be closely involved with the planning and implementation of inquiry-driven laboratories. At many four-year colleges and community colleges faculty members teach the laboratories as well as the lectures. This situation simplifies the implementation of inquirydriven experiments. The greater experience and deeper chemical understanding of the faculty allow them to guide students by drawing them out with strategic questions. Most research universities have laboratory directors or coordinators who plan the lab instruction and handle the dayto-day decisions. These staff members are often talented and vigorous teachers who want to promote an effective learning environment for undergraduate students. However, if the regular faculty are not also behind the concept of inquirydriven experiments and do not convey this support to the students and the TAs, it may be an uphill battle to make the change. All participants must become aware of the goals and methods of inquiry-driven lab teaching, including the faculty, laboratory directors, and teaching assistants, especially if TAs are the primary laboratory instructors and are not directly supervised by faculty members. Appropriate Training for Teaching Assistants It is important that graduate and undergraduate TAs understand what is expected of them, and they need to be supported in their teaching as inquiry-driven changes are implemented (17–23). If their teaching skills are not developed, the TA’s natural inclination will be to fall back into familiar patterns of instruction, and most likely the experi-
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ment will be conducted in a conventional cookbook fashion with the TAs reverting to the lecture, answer-giver mode they probably know well. However, with the appropriate training TAs can be effective teachers of guided-inquiry and designbased lab learning. Training graduate-student teaching assistants is nearly always a component of research university programs (18). For laboratory teaching, TA training often includes practicing the experiments that will be used so that they become familiar with what the undergraduates will be doing. This activity can be a springboard for the instructor to lead a discussion about ways to promote inquiry-driven learning goals and for considering the questions that students might ask during their lab sessions. The TAs need to understand their role of interacting with the students: giving assistance when needed, inviting questions, providing explanations—guiding students without giving the answers (24). TA training must help TAs think about their teaching and the many ways to be an effective teacher (19, 22). Providing some key articles describing the guided-inquiry approach and discussing these during training sessions or weekly lab instructor–TA meetings can reinforce the new teaching method (2, 13, 19, 23–25). Regular discussions and feedback on guided-inquiry and design-based approaches and the TA role in laboratory teaching will contribute to successful implementation. Teaching assistants must understand the goals and methods of inquiry-driven labs and they must support them, as well. This can be a challenge for TAs who are deeply engaged in their graduate programs and may wish to spend a minimal amount of time on their teaching obligations. Faculty research mentors may be in the best position to point out to the TAs that their thesis research might benefit by what they learn about the process of science from teaching inquiry-driven experiments and projects. The overall education of graduate students will certainly benefit from their teaching the skills of problem solving, data interpretation, and experimental design, which they also need to use in their research careers. Using inquiry-driven experiments could simultaneously strengthen both undergraduate and graduate education in organic chemistry. If TAs are the primary instructors in the organic laboratory and they are not directly supervised by faculty, openended inquiry experiments and projects present an additional challenge. For these projects to be successful, faculty members must stay in touch with the TAs throughout the experimental process. Open-ended inquiry experiments may be a step too far unless the faculty set up a reasonably elaborate process that can insure its success (26). Time for Pre- and Post-Laboratory Discussions Pre- and post-laboratory discussions are important parts of a student-focused, active learning paradigm (25). The prelaboratory lectures that most organic lab courses use to set the stage for experimental work will naturally become more discussion-driven to reflect the needs of inquiry-driven experiments. However, it seems more important here to focus on post-laboratory discussions, which are far rarer in occurence.
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When scientists have finished research experiments and evaluated the data, they get together to discuss their results, to give their interpretations of what they have discovered and to learn what others think about them. In this light, it seems counterproductive that one would use inquiry-driven experiments and then tell the students to go off alone to write their reports. The contribution of guided-inquiry experiments to student learning can be significantly enhanced by post-laboratory discussions before the reports are written. Facilitating post-lab discussions can happen in a number of ways. If experiments are carried out by small teams of students, it is natural for the team members to get together to evaluate the significance of their results, since each student is dependent on the data of the other team members for his or her conclusions. The students can compile the data for an experiment as a group and analyze the results. This approach creates a positive atmosphere in the laboratory as well as developing an attitude of teamwork. When more than one team has done related experiments and the class discussion is held before student reports are due, interest in the discussion will be high. If teamwork is not part of an experiment, the class can be divided into small groups of students where they can discuss their results together. The only additional necessity is to set aside a time for all of the teams to present their experimental results and interpretations to their lab sections. This scheduling of postlab discussions poses a challenge to some universities and most community colleges, where students depart in many different directions after the laboratory period has concluded. A response to this challenge is to replace some laboratory lectures with post-lab discussions. If a multi-week project approach is used, a pre-lab session may not be necessary every week and can be replaced with discussions of experimental results from the preceding lab period. In addition, projects have the flexibility to allow a longer time for class discussions from time to time. The discussions will also provide useful guideposts for students in the middle of their projects. Availability of Modern Instrumentation The availability of instrumentation is an important factor in using guided-inquiry experiments. Spectroscopy and chromatography make it possible to obtain definitive experimental data within the time constraints of the instructional laboratory. Infrared and NMR spectroscopy, plus capillary GC, are particularly important. It is also important to have the appropriate number of instruments available, so that students do not have to wait an undue amount of time to run the necessary GC or IR analyses. Class size is not a major factor with regard to these instrumental needs, as large classes are commonly divided into small laboratory sections. Rarely does the size of a laboratory section exceed 24 students; 20–24 students is common and will be the basis for our discussion. Our experience and that from a number of other institutions suggest these guidelines for instrumentation: • One FTIR spectrometer should be available per lab room. They are fast: 15–30 samples can be run in an hour.
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• Three to four gas chromatographs with integrators should be available per laboratory room, preferably capillary GCs for good resolution and ease of changing experimental conditions. • One NMR spectrometer should be available for undergraduate student use per institution. A large university may also need an auto-sampler to increase the throughput. It is not necessary for students to run their own samples, although it is helpful if they can process their own FID data, which can easily be sent to a computer room and processed with one of a number of software programs.
Research universities that are willing to devote a share of their instrumental resources to undergraduate laboratories have a substantial advantage in the use of inquiry-driven experiments. Although a large number of undergraduate institutions are also well equipped, many four-year schools and community colleges cannot afford an adequate number of modern instruments. This situation makes it necessary to develop strategies for guided-inquiry and design-based experiments that have fewer instrumental demands. One attractive approach is the development of experiments that can utilize multiple means of analysis, for example GC or NMR, or perhaps IR or NMR. Another possibility for smaller schools is brokering ties to larger nearby institutions, allowing the sharing of modern instrumentation. With the ready availability of Internet resources and electronic transmission of spectroscopic data, one can envision that technological solutions may help to solve the problem of the high cost of instrumental resources. Availability of Suitable Written Background Materials The quality of student materials written for inquirydriven experiments is important for the success of these laboratories. Materials matter! A major goal of question-driven, guided-inquiry experiments is teaching students how to extract knowledge from experimental results. The background scenario for each guided-inquiry experiment needs to identify the question being asked, its context, and the experimental data that can be used to find the answer. The expectations for the required data analyses must be at the right level for second-year students. A discussion sheet for the first few postlab discussions will teach the students how to prepare their presentations to the class. In addition, a well-written manual on the techniques of organic chemistry is critical, as are carefully crafted and well-written procedures. For a design-based experiment, the generic procedures that are adapted by students for the synthesis of specific compounds need to be carefully written. Giving the students background material on how to go about adapting experimental procedures will help them to see the thinking process that is required. Many colleges and universities use in-house organic chemistry laboratory materials. Some of these materials offer only a few paragraphs of context and background plus an experimental procedure. They would have to be carefully rewritten to serve as the basis for inquiry-driven laboratory experiments.
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Conclusions Chemical educators who implement inquiry-driven experiments will encounter challenges, as with any important curricular transformation. However, breathing new life into the organic laboratory experience is important, and we are convinced that guided-inquiry and design-based experiments and projects are an effective way to bring this transformation about. Teaching the art and science of data interpretation and experimental design, thereby giving students the opportunity to learn directly how the science of organic chemistry is actually done, is a worthy and achievable goal in research universities, comprehensive universities, four-year colleges, and community colleges. Note 1. Most of these and the following references are written in the context of introductory chemistry courses. Only a few published articles have discussed implementation of inquiry-driven organic chemistry laboratories.
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