Dynamic Organic laboratory Instruction
A
growing body of literature (1-8) indicates that there is widespread concern with the manner in which students are generally introduced to the study of organic chemistry. Lest it be argued-with reasonable justification-that this concern is misplaced because courses labeled "organic chemistry" will disappear from curricula in the not too distant future (9), I think it important to point out that the discussion has implications for the teaching of all fields of chemistry and other sciences at elementary levels. It may be that critics have singled out organic courses merely because there has been considerable uniformity in them throughout the country, and thus their glaring deficiencies lend themselves to generalization. I n my view, the essential defect of the traditional introductory organic chemistry course is that it portrays chemistry largely in terms of what chemists have already learned and packaged for orderly consumption. By stressing assured, static results, it misses the dynamic, investigative heart of science. This may to some extent reflect the unfortunate emphasis upon Answers which permeates American education a t all levels. Our reward system plays too heavily on the importance of arriving a t the correct answers to some artificially contrived problems. I n response, students see little reason to consider how they arrive at answers. Thus they are generally stymied when they meet problems that have not been suitably predigested. This ~esult-orientationis at least understandable in the lecture hall, but it is purely tragic iu the laboratory. Scientists should recognize its inadequacy, but unfortunately until very recently organic chemists commonly seem to have ignored this in their introductory laboratories. By and large, I think students have been more perceptive than their instructors in seeing what is really being asked of them. I n my own experience with several years of standard laboratory exercises, no amount of lecturing, individual conferring, or quizzing could convince my students that it really is important to understand why they carry out certain operations in the laboratory: I n their eyes, results were obviously all-important.' A result-orientation expresses itself in various ways: use of predictable, class-tested exercises emphasizing expected results; evaluation of student work largely on the basis of the product produced; a useless aim of 'In the words of a student: "The worst part of any lab is the feeling that I've got to do it right the very first time.. .. If somehow you could consistently, successfully woid the RightAnswer-In-X-Hours feeling, you've got it made." 2 Is this one contributing reason far the universal use of graduate students in university laboratory classes?
opinion exposing students to a myriad of known compound or reaction types; or a goal of acquainting students with a multitude of possible chemical hazards. The work settles into an easily-programed routine which is not only frustrating to the students, but particularly boring to the instructor, who must go through the same pattern year after year.% The Dynamic Dimension
If we are to escape the inadequacy of a resultoriented laboratory, we must place greater emphasis upon the dynamic activity of scientific experimentation. My own approach to the problem builds upon the principles elaborated below, some of which have been discussed previously (2, 5, 6, 8), aud others of which have not yet been stressed in the literature. Students must understand that experiments are not ends in themselves, but have value when they teach us something about a problem that needs to be solved, to paraphrase Fife's useful concept of "problemorientation" (6). This understanding makes for close, meaningful correlation between the laboratory work and what is discussedin the classroom. One very effective way of minimizing the drive to get The Right Answer is to devise experiments for which the answer is unknown (24, 25). When i t is unknown to the instructor as well, he and the students are drawn together into the learning process; the students no longer see their task as one of guessing what the instructor already knows is right. Logically, the work should be individualized, as Fang and Orz (8) have done extensively, so that whether working on their own private projects or on their independent facets of a class project, the students have only themselves to rely upon for arriving at answers. Individualized work eliminates the need for a "coolcboolc" manual and frees the students to use the library in seeking out, adapting, or designing procedures for their experiments. It also demands an open-laboratory policy to accomodate research journal procedures which have been developed with no thought of their possible suitability for three-hour periods, as Silberman and McConnell have noted in detail (5). These authors have also pointed to the special problems which may arise in the absence of an "official" textbook. Books designed for this type of course are extremely few (1012a) and limited in their scope. It would indeed be helpful to have available a more comprehcnsive text which offers background discussions of apparatus, technique, and general methods of attacking a variety of laboratory problems, without suggesting specific procedures to be followed. Hancock's recent survey of Volume 46, Number 5, Moy 1969
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thc org:u~iclitrr:ttnrr (15) may pmvc trscful to students in thcir cnrlg for;y.s into the libr:rry. I n a free-flowiug atmosphere the students teach each othcr a great deal, whcther through formal seminars, as Fife ( 6 ) wrd Kewman and Gassman have used (2), or simply through their informal conversations while morkiug on diverse projects. I n order to get a reasonably true idea of what organic chemists do, the students should grapple with a broad range of projects similar to the synthetic, analytical! kinetic, mechanistic, stereochemical, etc., problems that are dealt with in "real life." Such projects frequently can be used to introduce ideas which will later be taken up in the classroom in a more meaningful way than if presented purely in the abstract. I t should go without saying that modern inst,rumentatiou is indispensable for realistic work. A final principle, which has not received the atterrtion it deserves, has t o do with the way students' work is cvaluated in a laboratory coursc which is not resultoriented. More attention must be paid t,o asccrtair~i~rg what the students learn from a project, regardless of its outcome. M y practice is to require that they submit formal, journal-style reports for each project, which give a complete account of the work done, including a critical cvaluation of the procedure and results. This requirement generates some complaints, hut it effectivcly dramatizes the importance of clear communication of research results. Some Useful Projects I n departing from the traditionnl, res\tlt-ol.iented appranch, I found it rather diffintlt a t fiwt to gct w e d to the need for draslir reduetim in tlre number of expe~%nents. This ~.equirement a d the fact that the rontent of the course invnrirrhly chnnges f m ycnv to year continue to demand x great deal of thoughtful planning. Therefore, while recognizing that the choire of projects is a highly personal m e , I ofier some snggcstions from my own experience for ronsiderxtioli along with those of the anthow mentioned above. Xlosl students find exerrises in technique d ~ d lin any form," but thcy ran he tranrfotmed to simple itivestigation with the nddition of au ~nlktmvnfnrlov. Instend of having the whole class encow,ter i~ecrystxllimtion by pnrifying sampler of the same dirtied-up known rompowd, I hxvc issued n ~ ~ k n o w nawl s left to tho studenl the p ~ d , l e mof finding n suitable solve111(ldb). Likewise, simple and frnrtio~rxl distillatiou and gas-liquid chromntogmphy (glr)* can be inttwhwed togethe!. by having the stlalents segnl.ate n mixture of two onknnw~tliqnids, relying upon glr to monitm thesepav.ztion andshow theefiect.of afractionnling eohtmn. The rep.zrated liquids can be tentatively identified by boiliug point from n limited group of possibilities or, preferably, by glc cmnparison with known samples. At their own suggestion, st.,dents have often added refl.aciive index measurements l a the evidenre. 1 have always found stltdents attracted t o preparative experiments, pwhxps because they appreciate having something to show for theil. work, and therefwe I have songht ways to me such experiments without letting them become boringly repetitio~w. Since we encounter alkene chemistry early in the year, I havc i ~ ~ t r o d o r ethe d class t o preparstivo chemistry via hydrogenntim of a simple double-bond compound snrh as mnleic acid (14). Stndenls are intrigued by the apparatus and impressed by the general simplicity of hydrogenat,inn as they go on to mccsier rcaction mixtol.es in later p~mjecls.~ In s more typical prepustivc project, t.ho class works on R. single typc of reaction, bnt each student receives his own stnrl.ing compound (5, 8, 1%). Since starting materials are tnken almost at ~.nndomfrom the stockroom shelf, a st,ndent may find himself preparing an obscure or even uuknown compound. I suggest the scale of opemtion, hub the student is on his own t o choose reagents and conditions, sohject t o instrnctor's
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s;ppraval. The preparations snceeed and fail with about equal frequency. The failorcs generally lead to the most thought,ful reports, and the students concede t h a t they are more beneficial experiences. Having the entire class work on the same type of react,ion shows the students how misleading the tcxtbook discussions of "general" reactions can he and teaches them a great deal about a. particdar reaciion as they see their colleag~lesapply it t,o a. variet,y of structures. We have used bhis approach for oxidizing double-bond componnds; carrying out eliminstions reactions on alcohols and slkyl halides; nitrating aromatic c ~ m p o o n d s ;and ~ preparing secondary and tertiary alcohols by Grignnrd synt,heses. These preparative projects can be ext,ended with instruclive variations. For example, in the ca-o of the elimination reaetions, I have issued R corresponding alcohol and halide t o a. pair of students. They ran t,he respective reaet,ions, isolated the product or mixt,ore of products, and analyzed them comparatively by glc. I n this way they sometimes could identify alkene isomers even when the known rampoonds were not available for direct compaison. In their reports they interprebed meehanistieally the difference in product distribution shown by the two t.ypes of stat.ting material. I have often relied npon experiments which have appeared in t h e pages of Tnrs J o u n ~ . \ r . ,even though in some cases they artre not designed for individcml work. Among those best. received by the studcnts are Wright's carbon-14 tracer study (15), Ilunathen's s t ~ d yof the stereochemistry of menthol (6, lfi), and, t o a. lesser degree, Landgrebe's kinetic investigation of a reaction mechanism (17). Another of Ilunathan's experiments, the alkylation of benzene (18), served as t h e core of a class project whieh draws attention to experimental design (19). I have found that thin-layer chromatography (tlc) and colnmn chromatography seem t o be most. effectively approached together. I n a project, similar to hlarmor's (8, do), t h e stndent attempts to separate and identify a mixture of u~lknowncompoonds, using tlc to gat,her information about the natures of the components and t o suggest suitable elution solvents before scaling up for a prepsrat,ive separation on the coh~mn. This sort of project illominates bath the similarities and differences between the t,wo techniques. At, one time, in order t o bring in a n equilibritm study, I had the class determine the equilibrinm constanbs for esterification of a number of simple acid-alcohol combinat,ions (21a). This project has now found a home in orlr analytical chemistry course, where the stress is placed on accurate technique in t,he context of a prnblum of obvious interest t o student,^ who have studied organic chemistry.' 1)eterminntion of t,hc stereochemistry of an oxime (dlb) is another problem which has many possibilities. I have used it by first calling att,ention to the appropriate chapter in "Organic Ileact,ions" (292) t o give the student a feeling for the variety of ways in whieh a Beckmann rearrangement can be c a r k d out. He is then directed t o determine the configwstion of the oxime he prepares from an assigned ketone. He can rtm the Beckmann
Again from a str~dmlt: "l.nbs usually demonstrate that it!s easiel. on paper, whieh is another way of saying they a1.e excrcisos in techniq~le. If you tell budding young scietitists thcy are k i n g taught skill, their intellects ~ . r b r la t the snth and the interest disappears." The relatively i ~ v a p l l s i v e , dual-colnmn Carle Basic Gas Chrrrmatoeranh .. . has been a remn~.knl,lv reliable, st~~dent-p~xx)f workhorse thrm~ghontthe eowse. 5 Sitlee the compounds mentioned me hvdrr,ge~~ated within a few minntes wing palladium in ethanol, a Pan. .\ladel 3010 low-pl.essure hydlmgenntov servcs n rl:tss of 2: stt~dentsnicely on x 1.5 miu/student srhcdule. I)r. 11. L. Titns has wed cyclohcxene, which allows the studcnts to analpre for u~iehangod starting nlkene by glr. lAlthough we have escaped diwlptive accidents, ~nitrntion is hnmmdn~win the hands of a student who cannot find s rclisblc prr,cednl.e tu follow with his pwticulm. rompowid. This prnject, is 1 1 0 longer i l l use. 7 All w r n ~ u t a t i tlre project, "1)eIermitmtion of a n E q d i b r i w n Constn~>t,"hy E. J . Billingham, can be rhtaitlcd on reqllest frnm the New Expe~iment Clenrng Ilause, Advisory Co~mcil r m Cnllege Chemistry, 701 Wclrh H o d , Suit 1124, P d o Alto, Cdiinrnia !)4:104.
rearrangement by the method of his choice and identify the amide product by comparivon with synthetic samples he has made. The projects which have consistently generated the most enthusiasm are q d i t a t i v e andysis unknowm and a multistep synthesis. The unknowns may be any compounds listed in "Tables for the Identification of Organic Compounds" (8.9) and the student may use any fea~iblechemical andlor inst.rnmental attack. For each synthetic project I assign starting materids and the dtimate prodoct, leaving procedure and scale of operation to the student, who must plan and carry out a sequence which may range from two to eight steps.s By popular demand, at a convenient point in the second semester I have dlowed the students two weeks to repeat s pl.eviaus project, incorporating the criticisms and suggestions they made in their earlier reports. This gives them an indisputable evaluation of their andysis of the situation in a way more convincing t,han anything an instructor can manage. Additional benefits from rueh an opportunity have been noted by other authors (8, 6).
Student Reaction
I did not encounter the reaction of "mild hysteria" noted by Silberman and McConnell ( 5 ) ,probably because my studeuts had gotten a taste of this sort of work from their use of Gates' manual ( 1 1 ) in their freshman course. This raises a point about the effect of a problem-oriented laboratory course on the rest of the undereraduate curriculum. We have found a t Nevada Souther11 that after giving the students two years of investigative laboratory work, they expect-and rightfully so-to he similarly stimulated in their junior and senior years. This has led us to revamp our upper division course structure severely, deleting much traditioual technique-cxercise laboratory work in favor of au integrated program which will give students projects that draw upou scveral fields of chemistry. Every instructor who commits himself to this approach to laboratory instruction seems to get the same astoundinelv enthusiastic recention. The bieeest surprise to me was that studeuts at all levels of ability and accomplishment reacted in much the same positive way. There was no significant effect on the dropout rate. After initial complaints regarding the uncertainty of the working hours, an increasing number of students appeared voluntarily in the laboratory a t odd hours to refine or extend their work. Many have made the organic laboratory a quasi-headquarters on campus. They take a great deal of pride in work that they know is uot a rerun of what thousauds of students before them have done. illy own reward has come in seeiug what students may do when they are uuleashed or1 a problem that interests them. Two anecdotes will illustrate. At one point near thc end of the first semester I had assigncd the class Grignard syntheses and asked them to subject their products to both glc and ir analysis. Many of them were shocked to find evidence of much unreacted carbonyl compound and a significant amount of alkene. Early in tho following semester one student asked permission to subject his four-component Grignard product to tlc and column chromatography, iu place of thc usual artificial-unknown project in those techniques. After much tedious work monitoring the scparation by glc and ir, he finally identified the three major component,^. (It was necessary for him to im-
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provise a way of reconstructing the ir spectrum of his alkene in a mixture with the starting ketone.) He was rewarded with the discovery that his branched-chain alcohol, when finally purified, was indistinguishable in odor from Vick's VapoRub@. This led ultimately to some independent study of current research in the stereochemical theory of odor. On another occasion, several students found that their multi-step synthesis projects required them to reduce a variety of nitro compounds to aromatic amioes. Some of them set about the standard tin or iron reduction, or experimented with ammonium sulfide (which, on paper, appeared less tedious). One student, however, recalled his appreciation of hydrogenation some months earlier. Since this reaction receives scant attention in the textbooks, he asked to eheck its applicability to his nitrobenzene using a microhydrogenation apparatus. Here the rate and extent of hydrogeu uptake gave him hope, whereupon he scaled the reaction up and quickly got a clean 90% yield of amine. Those who had picked ammonium sulfide-and were getting no product-then switched to hydrogenation, and all of them got similar excellent results. Later another member of the class had to reduce p-nitrobenzoic acid but was dismayed to find it too insoluble in ethanol to allow the use of a colleague's procedure, which had worked nicely for the meta-isomer. A little thought, however, led him to try the reaction in aqueous alkali which led to the best yield of all, and provided another clear lesson in the problems of applying "general" reactions to specific compounds. (The news about hydrogenation as the "only" way to reduce a nitro compound got around so effectively that students in the following year's class turned to it immediately when faced with a similar synthesis.) Perhaps the students' reactions to this course are best expressed in their own words, culled from self-evaluation questionnaires gathered after the course had ended. From a psychology/philosophy major bound for medical school This course ranks as one of the best, I've t,akeken in 168 credits of college work. To say that t,he course is exceptional iis to have a remarkable grasp of the obvious.
From a chemistry major When I had a choice of lab or stndying-lab always went first; besides, I learned more there from things I did.
From a biology major I n general, I thought this was a darn good course . . .. While I am still a very far cry from even a mediocre chemist, this is the first time in all my vain attempts a t chemistry that I have some foggy idea of what is going on and why. I struggled through freshmen voodoo and was resigned to organic voodoo. Maybe I'm not very good at it, hut at least the voodoo is gone. Sometimes in my daily work I let tidbits of this new understanding run through my head for the sheer jay of knowing about it. I t gives me a sense of accomplishment I never had before. I never thooght I'd live to see the day, but I am actnally looking forward to my next chem course!!
Literature Cited (1) LAMBKRT, F. L.,J. CHEM.EDUC.,40, 173 (1963). (2) N ~ V M AM. N ,S., AND GASSMAN, P. G., J. CHEM.EDUC.,40, 203 (1963). (3) BATTINO, R., J. CHBM.EDUC.,43, 281 (1966). (4) SMITH,R . B., J. C H ~ MEDUC., . 44, 149 (1967).
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(5) SILBTIRMAN, R.,
(6) (7) (8) (9)
(10)
(11) (12) (13) (14)
A N D I\ICCONNI~LL, J. CHEM.EDUC.,45, 267 (1968). FIFE,W., J. CHEM.EDUC.,45, 416 (1968). T a \ u LNOVSKY, W. S., J. CHXM.EDUC.,45, 536 (1968). F. ~ iF.,, A N D Om, I). R.; presented a t 2nd Great Lakes Regional ACS Meeting; report,ed in Chcm. & Eng. News, 44, (J!lne 24, 1968). (a) YOUNG,J. A,, J. CHIIM.EDUC.,44, 564 (1967); (b) G R . ~ 11. , B., in "Selected Papers From Regional Conferences, 1966-67," (Serial Puhlicatian No. 35), Advisory Council on College Chemistry, Palo Alto, California, 1968, pp. 29-34. Y o m a , J. A,, "Practice in Thinking," Prent,ice-Hall, Inc., Englewaod ClitTs, New Jersey, 1958. G.LTES,H. S., “Laboratory C+uide for General Chemistry: A Research Anoroach." IIouehton MifRin Co.. Boston. .. 1962. (a) hl.rHMon, S., "Laboratory Gnide for Organic Chemistty," I). C. Heath aud Co., Bostou, 1964. (b) ibid., p. 185. HANCOCK, J . E. H., J. CHKM.EDUC.,45, 193, 260, 336 (1968). ADMS, X., A N D \'OORH&ISS, V., " O l g m i ~ Synthesw," (Ediror: BLATT,A. H.), (Znd e d . ) , John Wiley and SOILS, Inc., Ncw York, 1941, Coll. Vol. I, pp. 63-67.
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(15) WRIGHT,J. C., J. CHKM.EDUC.,40, 206 (1963). (16) D U N A T H .H. ~ , C., J . CHIIM.EDUC.,40, 20.5 (1963). (17) L A N D G R ~ ~J.BA,, I I , J. CHI:M.EDUC.,41, 567 (1964). (18) D U N A T H .H. ~ , C., J. CHI:^. EDUC.,41, 278 (1964). E. J., J . CHI:M.EDUC.,45, (19) SMITH,R. R., A N D BILLINOH.\M, 11.5 (1968). (20) i%HMoR, S., J . CHIIM.EDUC.,42, 272 (1965). H. W., "Selected (21) (a) HRLMKAMP, G. K., AND JOHNSON, Experiments in Organic Chemistry" (Znd ed.), W. H. Freeman and Co., San Francisco, 1968, pp. 54-5 (b) ibid., pp. 126-8. (22) L. G.. AND HELDT.W. 2.., "Ommic ReacLions.'' ~ - -DoNnnUMn. , (Editors: Cope, A. C., el al.), John Wiley and Sons, New York, 1960, Vol. 11, pp. 1-156. "Handbook of Tables for the Identification (23) R A P P ~ P ~Z.,~ T , of Organic Compounds" ( 3 4 ed.), Chemical Robber Co., Cleveland, 1967. (24) KIEFFER,W. F.,J. CHEM.EDUC.,42, 463 (1965). (25) RAMETTI:,11. W., J. CHliM. EDUC.,43, 299 (1966).
Robert B. Smith University of Nevada Las Vegas, 89109
