A Problem-Based Approach to Organic Chemistry Karl De J e s u s Union College, Schenectady, NY 12308 For quite some time our department has been concerned with the seemingly decreased capacity of incoming undergraduates to think analytically. Some contend that this trend continues even with our colleze eraduates. This was revealed in a recent study by ~ o d n e (1) r where shortcomings in the conceptual understanding of entering graduate students were reported. We have observed that, whereas intellectual aptitudes of students in the sciences have continued a t about the same level, their ability to formulate strateeies for the solution of difficult problems and to synthesize arguments supporting a hypothesis has decreased. Our concern i s that, if these shortcomings are not addressed specifically in our courses, we will be producing graduates who are less equipped to deal scientifically with the difficult problems often found in graduate studies or industry. In an effort to make our organic curriculum more interesting maiors and. a t the same time. teach m to ootential . them to think more analytically, we decided to experiment with a oroblem-based aooroach to oreanic lecture. This is not a nivel concept. ~ r & i e msolving Gas been successfully incoroorated bv others in the laboratow ( 2 ) and lecture comGnents (3-5)of organic chemistry. Black (4) a n d Heeren ( 5 ) even suggest t h a t spending the majority . . of class time guiding stizents as they ~ o l v ~ ~ r o b l eisr nsupes rior a s a teaching approach when compared to the traditional lecture. What the latter reports did not address specifically were methods of ensuring that analytical thinking was developed during the course. We wanted to focus on this issue while keeping a lecture format. We are far from convinced that a lecture format is the best form of presentation. Nevertheless, we wanted to compare results from our experiment with those of a traditional lecture class and desired to keep variables a t a minimum. Our department was suited ideally for this project because we normallv run two small lectures, 4 0 4 5 students, within a given term and these have a common final exam. This made i t possible to use the final exam as a basis for comparison between an experimental group trained i n analytical reasoning and a traditionally taught control group by checking for differences in performance on a wide variety of test questions. The main focus of the experimental class was to teach students how to approach complicated, essay-type problems and to solve them in a logical, concise, and thorough fashion. For this nuroose., lectures were centered around chapter summary questions. We further encouraged their development by introducing alternate modes of testing such as essay test questions, team problems, and takehome oroblems. These are described below followed by our findings ~~
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Lecture Format As mentioned previously, there were two organic lecture classes taught simultaneously and these were taught by different professors. The control class was taught using the format so common to most texts nowadays. In a tvoical ". chapter, functional groups were introduced and properties were oresented followed bv"preparation methods and reac.. tions. In addition to lecture, several review sessions were 224
Journal of Chemical Education
held when difficult material was encountered. After allowing some time for the solution of homework nrohlems from the text, students were tested. There were-four such examinations followed bv the final exam. While lectures for the experimental group resembled those of the control moup. the framework for the class was different. Each chapter was begun with a summary question. This was a multiple step, essay question purposefully formulated to encompass the most important aspects of the chapter a t hand. Our goal was to encourage students to analyze the material a s i t was being presented and determine if it was applicable to answering the question. In doing so, we hoped they would view new material with a more curious light and not the indifference which traditionally accompanies new factual material destined for memorization. Once all the chapter material was presented, solutions of summary cluestions were discussed. In the initial chapters every efibri was made to develop strategies for the solhtiou of these questions. In addition, a lot of emphasis was placed on the written presentation of solutions. Here, the message was that a logical progression of statements or deductions needed to be developed that led to the final conclusion or answer. In order to guide students further in their analysis of cluestions. strategies, and new problems were discussed in session once a week. Half of the pean additional riod was dedicated to solving textbook problems while the other half introduced mar; complex problems t h a t targeted principles covered that week. Testing Methods Essay Test Questions Most traditional methods of student evaluation involve examinations with short answer questions. While these can be used to test knowledge of principles, mechanisms, or synthetic reactions, they usually place a premium on the abilitv to memorize and retain information rather than its application. While we believe that these types of questions are useful.. thev " do little to test the skills we were so intent in having students learn. For this purpose, we inserted into exams essay questions resembling the summary questions asked a t the beginning of every chapter. A typical question would have three or four parts and require students to explain why, for example, slightly different reaction conditions gave different results. Each part was designed to guide students through the solution by asking them to compare the mechanisms for each reaction and look a t electronic, conformational, andlor steric differences. Team Problems Several years ago the author needed a medium whereby some verv noor students could studv together without acsort of stigma. At tKe tyme, t h e solution quiring seemed to be forcing everyone i n the class to study together. The problem was finding a method that would challenge all those involved. Team problems seemed to be an ideal solution. Since then our department has found them
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to be a very useful tool for teaching the most complicated principles in chemistry. The format involves splitting the class into groups of students having equal proficiency i n t h e subject. These groups, or teams, usually range from four to seven people with four being a critical mass. Each team is given a problem which, individually, is extremely challenging but can he solved a s a a o u u . The solution is oresented as a oanel outside of class in which every individual is responsible for all facets of the solution. During this panel discussion the instructor takes turns asking questions of every student. The final score is a com~ositeof all individual answers and is given to all team members. Because our institution runs under a 10-week term it is usually not possible to do more than one or two team prohlems a term. Therefore, these are reserved for the most difficult subjects. As such this is usually done in the second half of the term, thus allowing plenty of time for previous student evaluation. Once individual proficiencies are established, the a r t comes in designing the problems properly. Typically, the problems are built around a set of principles or questions that the instructor wants to deal with durine all nanel discussions. As a result. most team aues, tions are multistep and interweave many principles. The better students get very sophisticated applications of these principles. In the past we have experimented with having the panel discussions during class and welcoming questions from the class. This approach was not as successful because students rarely asked difficult enough questions to ascertain student understanding in depth. "
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Take-Home Problems One of the downfalls of grading solely by examinations is that this evaluation process does not provide alternative measures of progress for individuals with poor testing skills. Most of us have witnessed the intuitive laboratory student who continually underachieves i n formal examinations. Take-home problems provide a n additional venue to gauge performance while, a t the same time, presenting instructors with a mechanism to ask essay-type questions without any time restraints. This seemed to be a perfect way to probe total understanding. One problem that quickly arose was the inherent conflict in uhiloso~hiesbetween team oroblems and take-home problems. In one case we encouraged teamwork while in the other we expected individual effort. We recognized that they would inevitably work together and so we allowed it, provided groups did not exceed eight members. Students were, therefore, encouraged to work in small groups of their choosing and required to hand in one paper with all participant signatures. Curiously, groups never approached the limit and papers were rarely identical. Joint Final Examination The final examination provided the only source of comoarison between the control aouD . and the ~roblem-solving class with both instructors contributing material. To avoid anv unnecessarv burdening of the control class. the format wis 85 percent short answer questions a n d l 5 percent Ionper The latter portion was com~osedof a n - auestious. . essay question and a mechanistic question. In the essay question they were asked to rationalize the regioselectivity df an electroihilic aromatic substitution, compare its rate with that of another aromatic compound and, finally, explain the source of the difference in rate. The second question was more traditional in nature and simply asked for the mechanism of a specific carbonyl addition reaction. Results from each of these questions were tabulated for each class and compared.
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Discussion As our experiment proceeded we were able not only to gauge student progress in their analysis of complicated questions but also to evaluate the different facets of our program. For example, our observations during private consultations and problem sessions were t h a t chapter summary questions in lecture, while valuable examples of possible test questions, rarely were used by students a s the study guide we intended. Rather, students would wait until the answer was oresented in lecture and studv that for
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of information &at is characteristic df a scientik On the other hand, students responded favorably to the optional studv sessions with a remlar 30-50% class attendance. Here, participants found the time spent on strategy and approaches to problem solving more useful than simply going through questions in the text. This seems to indicate that formal lectures may not be the best format to achieve our goals. Perhaps a n adaptation to t h e approaches of lkahanovsky ( 3 )and Shearer ( 6 )would be appropriate. In this case, study aids could be used to open up class time for problem-solving sessions. As we examined the different testing methods we found several drawbacks. This was es~eciallvthe case for the essay questions found in examinations. As expected, students were apprehensive about tests and found these questions intimidating. Their lack of familiarity and resulting discomfort toward these types of problems only underscored our tenet concerning'the lack of trainingin scientific reasoning for most introductory science courses today. Nevertheless, the major disadvantage found in these types of questions was an increase in grading time of 50 to 100% when compared to short-answer questions. This was alleviated to some extent by continuing to ask short-answer questions for half of the exam. Even so, it is quite clear that this approach will be difficult to implement in large classes where hundreds of papers must be graded. Increased time commitment also was a concern with the team problems because several out of class panels must be scheduled and these usuallv last about an hour. It was a lesser obstacle with take-home problems because groups were allowed to hand in a common paper. While there is no denying that many of the testing methods increase instructor time, we still have found their implementation meritorious. This is backed up by a dramatic improvement in student performance on examinations given during the term. In the later examinations their answers were better supported and organized. The team and take-home problems catalyzed the formation of several study groups and those who took full advantage of these saw a marked improvement in performance. Team problems were particularly useful because they targeted the difficult chapters on carbonyl chemistry. As a whole, the class had a better grasp of this chemistry than previous ones whose team problems did not cover this section. Enthusiasm for team problems was shared by the students who often commented in student evaluations that team problems were helpful as learning tools. Although there were indications that student's analytical reasoning was improving as the term progressed, i t was possible that this was the result of maturation in the subject matter. Because one would expect both the experimental and control erouns to mature a t the same rate. the final examination gave a clearer indication of the effectiveness of the Droeram. As we comoared the final examination results f& bGth classes there here two issues that we wanted to look at. The first. of course. was to see if there was a clear trend indimring that t h r prohlm-wlvin;: class had i dcnlandcd logl1r:irnmd 10 ptdrrrn 11t.tterat q u c i t ~ o nthat -
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Volume 72 Number 3 March 1995
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Final Examination Results Subject (points)
Experimental Class
Std. Dev. Control Class Std. Dev.
A%
Class Average (235)
146.5
32.3
125.2
37.2
Essay Question (20)
12.9
5.2
6.1
5.8
110
8.0
2.0
5.3
3.4
53
Mechanism Question (10) Shot1Answer (205)
125.6
113.6
17.0
10.6
t h a t they would have done a s well bad another instructor written the essay questions for the final. Nevertheless, the disparity i n performance shows conclusively t h a t t h e experimental class was more adept a t answering essay-type questions.
Conclusion Although we are not optimistic t h a t a prohlem-solving lecture format infused s t u d e n t s with added curiosity while learning class material. our results show cal analysis and had improved their ability to defend a sothat a problem- based approach to organic chemistry will lution on paper. The second, more subtle issue, was to deimprove the ability of students to tackle complex questions termine if the prohlem-solving class ahility to answer in the science. Judging from the quality of their solutions short-answer questions had suffered a s a result of their we also can conclude that analytical reasoning skills also training. I n order to address both of these questions avermust have improved. Furthermore, as shown by the sucages were tabulated for total score, essay questions, and cess in short answer questions, the continual effort to anashort-answer questions. The results are summarized i n lyze problems i n depth did not come a t the sacrifice of the table. breadth in the field. As the averages show, the experimental class showed a As mentioned previously this approach has its limita110 percent increase in performance over the control class tions. The main one is the time commitment exacted from in the multiple-step essay question and a 53 percent inthe instructorisi. We believe this a ~ ~ r o a can c h be i m d e crease in the mechanism question. Moreover, the standard mented with good results in smalf ;nstitutious with'ordeviations for each of these questions indicate a bit more eanic lectures of less than 50 students. This was the case clustering for the experimental class. We were not able to in our institution with a class of 45 students. We predict, calculate standard deviations for short-answer question however, that a s lecture classes approach 100 students or scores but class averages show a slight, 10 percent, inmore test grading will become unmanageable, and i t will crease in performance for the experimental group. be more difficult to schedule team problems. In such cases perhaps greater emphasis can be given to group projects We believe t h e first two figures a r e significant and such a s the team problems. We stronelv clearly show t h a t students i n t h e experimental class -. encourage - their use, whether in recitation sections or a s special projects learned how to approach complex questions more effecgraded by teaching assistants. We believe they will intivelv. I t was gratifvine - - to find t h a t the same students crease camaraderie within the class a s students find the wereable to reproduce mechanisms more effectively than atmosphere more conducive to group work. the control class. Usually, mechanism questions are low Our own students admitted that the added effort exscoring affairs but, by requiring constant consideration of pended during this project allowed them to learn the submechanistic factors in their reasoning, students improved ject matter more effectively. their learning of specific mechanisms. Finally, while it might not be desirable to devote a whole Of less significance a r e the figures for short-answer course to the development of analytical thinking, i t is questions. Clearly, t h e problem-solving class fared no equally undesirable to teach one devoid of it. We suggest worse than the control group. Nevertheless, one should not a n occasional. in-deoth aualvsis of a vroblem in lecture. be quick to conclude that they generally will fare better. accompanied by a n equally complex graded question, Because the population of our lectures is not totally uniwould go a lone wav in helpina our maduates think more form, i t is not unusual t h a t average final examination scores will differ by as much as 10 percent between two classes. Acknowledgment At this time i t is only fair to qualify the significance of Special acknowledgement should be given to J . Sowa for our results. I t should be noted that the exverimental class his patient contribution as instructor of the traditional had many advantages over the traditional class. For examclass a s well as to C. Scaife and L. Hull of the chemistry ple, while the traditional class did have review sessions, department for their support of this project and their valuthere was no formal training on how to answer complex, able comments. multivle-steo questions. The experimental class also had additional o;t-&lass contact time in the form of a team Literature Cited problem vanel and there was no effort made to compensate 1. Bodne~G.M.J. Chrm. Edur 1991.68.38MRR. kor this. Moreover, essay questions in the final exam were 2. Cooky.J. H. J. C h e m Educ. 1991.68,503-504. 3. Trahanovskv. W.S. J. Chrm. Educ. 196845.536. written by the experimental class instructor. Obviously, 4. Black.K.A,> Cltrm. Edue 1993.70,140-144. students in this class were familiar with the instructor's 5. Heeren, J. K.J. Chem E d u r 1990.67,330331. 6. Shearer,W R. J ChamEduc. 1988.65,133-136. questioning style giving them an advantage. I t is not clear Joint Average = 137.1 Final examination results for both the Exoerimental and Control classes.
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