Stanley J. StorFer and Ernest I. Becker Polytechnic Institute of Brooklyn Brooklyn I, N e w York
Teaching Techniques in the Undergraduate Organic Laboratory
It is paradoxical that the instructor must strive continually to inspire and sustain the student's interest in the first year organic chemistry laboratory, since many students first become attracted t o chemistry through their interest in the products of organic chemistry-colors, antibiotics, fibers, explosives. Yet, the introductory year of organic chemistry laboratory often fails to capitalize fully on the interest first aroused by these "magic" names. The challenge to the imagination is seldom awakened by the required experiments. On the other hand, in our opinion, qualitative organic analysis and quantitative inorganic analysis courses generally arouse more student interest. I n the former, the student is on his own and the successful solution of unknowns provides strong stimuli to his interest and imagination. In the latter, the acceptance of an analysis by the instructor is a good reward for the care and patience the student exercised which otherwise might be labeled drudgery. Ordinarily, the organic laboratory possesses neither of these provocative features; most experiments succeed to some degree and high precision is not required. As a result the student generally has had little regard for the organic laboratory. While awareness of this problem is not novel ( I , $ , S), few countermeasures have crept into the usual laboratory course. For a number of years we have experimented with methods hopefully designed to recapture student interest in the organic laboratory. The purpose of this paper is to report on these various experiments. The primary objectives in the organic laboratory course are to instruct the student in the principles and practice of laboratory procedures, to acquaint him with representative syntheses of organic compounds, and to allow him to study the physical and chemical properties of certain classes of organic compounds. In addition, we expect our students to operate safely in the laboratory and to enjoy the work. In an attempt to determine attitudes toward the experiments and to the course, students were invited to submit answersanonymously to the following questions: (1) What experiment did you particularly like? Why? (2) What experiment did you dislike most? Why? The replies showed definite trends. Experiments ~vhichdealt with techniques for the purification of organic compounds were considered to be boring and without apparent purpose. Preparative experiments were described as "cook book" recipes since the p r o w dures and results were outlined in the laboratory text. 614
/
Journal o f Chemical Education
The students also felt that experiments which demonstrated the properties of classes of organic compounds were a waste of time since the text discusses these subjects thoroughly. It is apparent from these comments that the students had little or no motivation to perform the experiments conscientiously. Replacing the most disliked experiments with different ones would result merely in substituting one set of "cook hook" recipes for another. We were convinced that the purposes of the experiments were worthwhile and necessary. We chose to modify the experiments wherever possible to introduce an element of the "unknown" and thus to raise student interest by giving him a greater responsibility in the outcome of the experiments. Chorocterimtion Experiments
The experiments which demonstrated the properties of alkanes and alkenes, aldehydes and ketones, anlines, and sugars were severely criticized by the students. Because they knew what to expect from known compounds, they resented having to run experiments on them even though the necessity of doing so was carefully made in the oral laboratory instructions. To obviate this resentment we eliminated the requirement of performing the known reactions and decided that only solving the unknown would be graded. Each student was given an unknown which was to be classified as a primary, secondary, or tertiary amine or as the corresponding hydrochloride. They also were asked to prepare two derivatives of the unknown and to report the melting points. Bonus credit was offered to any student who could correctly identify the compound from the data. All the students proceeded to attack the unknown. After about three hours of fruitless and generally aimless labor, they went to the knowns to learn what the standard tests really look like. With this experience, they went back to the unknown and solved it easily. In the experiment on sugars, known compounds were again made available. The etudents determined whether their unknowns were reducing or not, and prepared phenylosazone derivatives. They were given bonus credits if they used additional experiments and thereby identified the sugar. The important point is that most of the students now went to the known compoundsfirst and then to the unknowns. Two unknowns were distributed for the experiment on aldehydes and ketones. One contained a carbonyl function while the other did not; the student had t o determine this. With the carbonyl compound in hand, he then had to characterize it as an aldehyde or
ketone and to prepare two suitable derivatives. A bonus was awarded if the carbonyl compound was identified from the information obtained. By this time, the routine procedure of working with knowns fist and then unknowns was universally followed. The experiment on alkanes and alkenes, in which the student received two unknown samples, was performed by all, quickly, and with interest. Procedural Experiments
Only limited success has been achieved to date in our attempts to encourage the students to perform conscientiously those experiments designed to teach laboratory technique. The use of unknowns in the melting point experiment afforded satisfactory results; however, similar techniques were unsuccessful when applied to crystallization and extraction experiments. The experiments demonstrating distillation and fractional distillation techniques were well received partially because of their simplicity and partially because their importance was illustrated by scheduling a preparative experiment, which required proficiency in these techniques, immediately afterward. Steam distillation was well liked because it involved the isolation of a natural product (citral from lemon grass oil). Preparative Experiments
More difficult were our attempts to enliven the preparative experiments with an "unknown" aspect. The greatest success, achieved accidentally, involved the synthesis of benzopinacol by the photochemical reduction of benzophenone. A recent case of poor logistics resulted in an inadequate supply of isopropyl alcohol, the recommended solvent and reducing agent. In order to make the best of an unfortunate situation, we asked the students to select and employ any primary or secondary alcohol in the chemical warehouse, adjust the laboratory procedure accordingly, and report the results of their observations. We emphasized that we could not predict the outcome of each experiment and, consequently, a poor yield would not reflect on their .ability, but would enable the class to determine for themselves just what conditions would be best for the performance of the reaction. The students selected methanol, ethanol, n-propyl .alcohol, isopropyl alcohol, see-butyl alcohol, and butane1,3-diol as the alcohols to be studied. One student elected to use an ultraviolet lamp as the light source in -order to compare its efficiency with that of sunlight. The results showed that isopropyl alcohol was the best reducing alcohol and that the ultraviolet lamp gave .a better yield in shorter time than sunlight. The students were enthusiastic about their contribution. Of course, the theory behind the results was presented :in a brief discussion. Special Experiments
For a number of years we have included a special preparative experiment as part of the regular assigument. "Special" simply refers to a compound taken from a suggested list not in the text (4). As is custom.ary in such cases, the student carried out a literature search and, after a conference with the instructor, went to the laboratory. The teaching time required in this ;technique was nearly prohibitive.
To relieve this situation we enlisted the aid of a number of research and teaching fellows in the following way. At the beginning of the semester we polled a few of the faculty to obtain a list of compounds which would be useful in their research programs. Additional criteria for selection were that the compounds were not available commercially and that each could be made in from two to three (5.5 hr) laboratory sessions. A number of graduate students were invited to take part. The course students then selected a compound, interviewed the graduate student who was interested in that compound, and finally carried out the synthesis in the laboratory space of the graduate student. With this one-to-one instructor to student ratio, the student got personalized instrnction beyond what could be given within the limits of the laboratory course. The graduate students, with their vested interests in getting the products, spent a good deal of time teaching laboratory techniques and seeing to it that the experiments were carried out properly. Further, they told the course students what would be done next to the products and so exposed the course students to a glimpse of a research program. We had tried using research compounds for the special experiments in previous years. The students, however, had felt they were being exploited. In the current organization this feeling was obviated because they appreciated the objectives for the compounds and because they got such intensive laboratory help. On the last day of the semester the course students were assembled and each presented briefly his special experiment. All the students took notes, thus broadening the scope of the teaching. To establish control, a question on the final examination asked for the equations for two out of three of the special experiments, omitting, of course, one which the student had performed. Discovery Replaces Drudgery
The outcome of introducing the "unknown" in the majority of the experiments has been enthusiasm for and better training in organic chemistry. The students relished having the responsibility for making discoveries on their own. They enjoyed carrying out control reactions as well as solving unknowns because their personal experience had brought home the necessity of doing them. Particularly, they liked working Mith a graduate student where they were exposed to a research program. Several students suggested-and performed-additional experiments related to their special experiments in order to "round out" their knowledge of the subject. As they gained confidence in their ability to perform an experiment, observe it, and draw the appropriate conclusious, their questions changed from "What is supposed to happen?" t,o "Why does it happen?" Literature Cited
(1) CHITTUM, J. W., J CHEM.EDUC.,8, 2408 (1931). (2) COGHILL, R. D., AND STURTEVANT, J. M., J. CHEM.EDUC., 14, 68 (1937). (3) DORRIS,T. B., AND O'CONNOR, U'. F., J. CHEM.EDUC., 18, 178 (1941). (4) FIEGER,L. F., "Experiments in Organic Chemistry," 3rd ed., rev., D. C., Heath & Company, Boston, 1957.
Volume 36, Number 12, December 1959
/
615
