provocative opinion Provocative Replies: Two Organic Chemists Look at Organic Chemistry Lab Chemist I: "I believe they can learn problem-solving and 'cooking' together-it's situation."
not an eitherlor
Marjorie Kandei State University of New York at Stony Brook, Stony Brook, NY 11794 Well, Pickering, I'm glad you had a chance in midlife togo back to re-experience the pleasures of intro organic lab. I always look forward to reading your articles about pedagogy-you think clearly and you write entertainingly. But I believe you missed something when you turned your observations into a Provocative Opinion-"A Physical Chemist Looks a t Organic Chemistry Lab" (Pickering, M. J. Chem. Educ. 1987,65,143-144). There is a sharp divergence between organic chemistry as taught and organic chemistry as practiced.. ..Organic Labs have degenerated into cooking.. . .A cook is concerned only with the ereation of a product while an organic chemist wants the answer to a question. You missed how we are asking students to use their minds in lab, even when we are not asking them to identify an unknown compound. (I hope my students do learn some traditional and some modern techniques so that when they go out into the world they won't embarrass me. And I believe they can learn problem-solving and "cooking" together-it's not a n eitherlor situation.) ~. Although you champion assignments consisting of unknown identification, I believe you'd agree that the important goal of such assignments is that students formulate auestions and think of wavs to solve problems. The fault of many organic experiments seems to he that there are no questions asked and no thinking done, only instructions given to allow students t o obtain products whose properties are matched to known values. I'm not sure that even the most mundane experiments are as had as they seem; it's probably partly the way they are written, not what is actually going on when they are performed. I'd like to share with you what I believe is going on when a typical nonmajor nerforms a crvstallization experiment in the third week of our lab course. The student knows he will have to turn the product in for grading. Among other things, we will weigh i t and compare the vield to that obtained bv other students. We will determine its purity by appearance, and, if it looks good, we will further check it bv melting point. So he is trying to get a high yieldof pure product, and-heshould accomplish thftask in a single lab period. Even thouah directions are . exwrimentul . the student will not he successful without asking himself questions a t several points and from his conclusions deci&ng what to do next. Through such a feedback mechanism he can influence his results and consequently his grade. I t is our responsibility as teachers t o write and to grade our ~~
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experiments so that students come to act in this way. During the lab session, we have to resist the temptation to give orders. Look a t a single step in the crystallization experiment, a Norit decolorization. The Norit is supposed to be hot-filtered out, but the step is tricky, and often there is a little of the charcoal that gets into the collecting flask. Among other questions, the student should stop and ask himself, "Have I separated solid from liquid?" There are quite a few possible outcomes. (1) The solution is perfectly clear--the filtration was satisfactorily performed. (a) The student observes the desirable state of affairs and proceeds, happy in the knowledge that he has accomplished the task as quickly as pwsible. (b) The student proceeds mindlessly,not bothering to evaluate the result--it works this time hut there are lots of other steps to go in this and in other experiments; such a modus operandi will not generally pay oft (2) The solution is gray-the filtration was imperfectly performed. (a) The student immediately observes the undesirable state of affairs and immediately performs a second filtration more carefully. Almost as good as (I), but Losing a little more material and taking mare time. (b) The student doesn't observe the gray coloruntilthe crystals form. He has to reheat, refilter,and recool. Almost as good as (a),but taking more time. (c) The student doesn't observe the gray until the crystalshave been collected. He has to redissolve,reheat, ete. Losing the most material and taking the most time. The above example assumes the student will strive for purity, and that is in fact what we encourage by counting i t more in the grading. However, there is a point a t which yield and time considerations make trying for higher purity impractical; the student has t o determine this point. And of course some of the students never notice the gray. The process is one of question, observation, evaluation, and decision. Note that the process recurs a t other steps, so the entire experiment is ver; complicated. Although ail students have the same instructions, it's not an exaggeration t o say that each student i~ doing a unique expe&nent. T o appreriate the variety, you ihould see the 200 vials of products from the class. We get everything from rolorless to gray (from the Norit remaining) to yellow (from the colored material not removed bv the Norit). That's not even considering the crystal form (heedles, pokder, or mush) from good or poor decisions a t other stage@of the experiment.
"Technique" can he separated from prohlem-solving, hut thev're eraded toeether when we erade products. In the area of tkchnjque, lab like cooking, driviig, or playing tennis. I don't think this is had. They are all activities where the mind and body act together to convert ohservations into actions, sometimes unconsciously. I often try to overcome lab anxiety by asking astudent what she likestodo and then saying "Oh, you'll enioy lab and he good at i t i t . . organic . musthave a lot in common with hang-gliding." There is a further important area explored in depth in the organic lab--the philosophy of keeping a record in a notebook. Because of the size of the classes and the quantitative nature of the experiments, I believe many large schools don't emphasize the notebook in freshman lab. It's not even notehook-keeping as a skill, which we may take for granted hut has to he taught, so much as its importance we are teaching. We can motkate our students by giving experiments l o k and complicated enough to make a good written lab record aooreciated. A sinele exoeriment with multiole trials to find an appropriate crystallization solvent will make a convert. (We exoect and tolerate some backslidine.) When we teach the notebook as alah record instead of a convenient place to write UD renorts. we can also show the difference between an ohservitioi and'a conclusiou. We thus address the objection you had to "teaching lab experiments to 'illustrate' a me-
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chanism." Observations stand; make new ones if necessary, hut don't expurgate. Feel free to change conclusions, among which may he the worth of certain ohservations. I agree with you: "Let the student think about procedure in lab and theory after lab." What we have to do is insist on a good record in lab and thoughtful written conclusions at a later time. on a renort or auiz. ~ c t u a l l yfiickering, , experiments with unknowns are popular in oreanic lab. At the end of the course. identifvine an unknown-from its physical, chemical, and spectrbs&pic properties gives students the sense that they have acquired enormous power to solve a problem. However, the questions that thev are askim themselves as they work are the same as those appropriate in extraction, synthesis, and purification experiments: What is this stufr! Is it pure? What's going on here? What should I do now? From strairhtforward sinelepurpose experiments, the students have gained experience examining their prejudices and thinking on their feet. Major reasons for the popularity of unknowns among teachers are how easy the grading is and how easily students are convinced of its fairness. If we want to, we can grade other aspects of lab ~erformancebesides obtaining- the right - or wrong answer, and we can convince students of our ability to doso. Then thev miaht be able to appreciate the intellectual content of a cr&.a&.ation experih;ent as representing an important aspect of our discipline.
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Chemist II: ". . . an equilibrium between theoretical and practical aspects of organic chemistry should be established." Raphael lkan The Hebrew Universlty of Jerusalem, Jerusalem 91904, Israel
I have read with interest the personal reflections of Miles Pickering entitled: "A Physical Chemist Looks at Organic Chemistry Lab" (J.Chem. Educ. 1988,65,143). He certainly provoked me to reply to some of the ideas put forward in that article. It was indeed a pleasure to read that a physical chemist had the guts and the courage to venture into the world of an organic chemistry laboratory with five students and a black cat instead of having a good time by theseashore. I have been wondering about the origin of the black cat's name "Steroid". In mv ooinion it mieht be the late L. Fieser's (from Harvard university) symbol of Siamese cats, which he ~ossessedand which he used on the front . page - of his populh books on steroids and natural products.. . . I should like to inform I'irkerine that during his lapse of two decades from organic chemistri, it has undkrgone-revolutionarv changes in various aspects of this science. Pickering claims that "The lab is not a good way to illustrate abstractions. . .".The organicchemistry lab and the modern organic chemist now uses organ-physical techniques such as 'H, 13C nuclear magnetic resonance spectroscopic, mass spectrometric, X-ray, and electron microscopic methods ( I ) . Thus, today, minute quantities are sufficient for GC/MS techniaues to reveal the constituents of natural ~roducts. For example, 700 different organic compounds weie detected in oil of coffee and 800 in beer. Another fact stressed by Pickering was "Our lahs show what oreanic chemists do with their fingers, hut not what they do with their hrains. . .".This approach might fit every lab work that involves, of course, some practical dirty. finger. work. The students are now requested by their instructors to understand the theoretical background of the practical work. Furthermore, a series of experiments on an advanced level have been, and still are, being introduced into the organic chemistry lahs. These include various interdisciplinary fields such as, for example, natural product chemistry
(2),biochemistry, and geochemistry. The students are also asked to design series of experiments as synthetically feasible routes to certain products. The student would have to give considerable thought and would involve literature and patent searches. Kozma (3)has shown that the recipes lab is preferred by students. However, in our organic lab (for chemists, biologists, as well as the medicinal scientists) we have waived the lahel of cookiue from the lah, since the students have to pass a brief exam involving theoretical and practical aspects of the particular area of the lab subiect rollowed h y a 3040-mindiscussion. After the lab workthe students are reassembled to discuss further the results of their practical work. The compromise of "let the student think about procedure in the lab and theory after the lab" contradicts our experience in teaching practical organic chemistry, which supports a "sandwich" approach, that is, theory-lab-theory. Thus the lab work is "sandwiched" between two theory lessons and a discussion. Our grading system is focused principally on the understanding of the subject matter. Overemphasizing the theoretical aspects and minimizing the practical work may lead to a situation where a student will he an expert on drawing mechanistic arrows of reaction pathways and not being able to perform effectively the practical work in the lab. The conclusion is that an "equilihrium" between the theoretical and practical aspects of organic chemistry should he estahlished. The claim of "why not keep the identitv of the white powder unknown" d&s not ex& in our lahssince the isolation and identification of unknowns is as integral part of the analytical organic chemistry lab experiments. It is proposed that a micro-, semimicro-, and macroscale of organic practical experiments involving purification and sep&atioi techniques together with modern and tandem spectroscopic Volume 66
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methods will attract the students to the wonderful world of organic chemistry. This approach has, indeed, been used in our labs in recent years ( 4 ) and bas proved to be highly successful. The microlab approach has also been offered by Ma (5),Pickering (fi), and others. In conclusion' I like to cite the late David Bergmann in that "Despite the growth of theoretical chemistry, organic chemistry will remain an art for a long time to come." Many life scientists do agree that organic chemistry has a charm of its own and is tightly associated with many
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scientific fields such as pharmacy, biochemistry, botany, zoology, medicine, and biotechnology. Literature Clted I. lksn, R.;crammer, B. - ~ ~ i ~ c h c ~ i . t compund ry: ~eteetion:in~ne~~~opedio of Physical Seienea and Technology; Academic: 1987;Vol 10, p p 4 M 9 . 2. Ikan, R. Noturd F?oducts,A Laboratory Guide. 2nd ed.: Aeademic: 1976. 3. K ~ R.8.~II R . ~. .SC;. T P ~ C ~1982.19.261, . 4. Ikan, R.Chromntogrophyin Organic Microomlysir.A Lobomtag. Guido:Aurdemie: 1982. 1976. Ma,T.S. Mi croaca lPMonipvlofiiiii Chemielry; 6 pickerins, M.: L.Prsde, J. E.J. Cham. Educ 1986.61,535.
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