Roberl Silberman
and James McConnell State Un~vers~ty of New York Cortland, New York 13045
A Laboratery Course for Organic Chemistry
I n recent issues of THIS JOURNAL there have been articles discussing changes in basic chemistry courses. Ross,' in an article on the changing chemistry curriculum a t Brown University, discussed some of the changes in the organic chemistry lahoratory. Smith2 reported a t some length on the change of approach to organic chemistry lectures and 1ectut.e material. I n his article, Smith stated that the lahoratory was still one of the weak points in the course. We have recently begun to remodel our organic chemistry course and in the process have greatly changed the laboratory section of the course. The modified lahoratory seems to complement the newer lecture methods advocated by Smith and more recently by Battino.$ Our basic approach was to design a lahoratory that would acquaint the student with "Doing Organic Chemistry." By this we mean not just simple lahoratory techniques hut also something of the spirit and fascination of the suhject and of research in the suhject. A standard laboratory usually acquaints the student with basic techniques and methods of synthesis for a variety of simple compounds, but often leaves little for the student to think about. Therefore, we did not use a standard lab text, hut proceeding on the premise that ideally a lahoratory should allow the student to exercise his mind and his imagination while using his new knowledge, we tried to challenge the student to try something different. With this in mind we have tried to design a laboratory course in which the individual student designs and/or selects a large numher of his own experiments. Our organic chemistry class contained 60 students which were divided into four lahoratory sections. Formally the course was divided between one and one-half faculty members. I n actual practice a strict separation of laboratories was not adhered to, as explained below. Our course began in a conventional way with a conventional experiment, the separation of caffeine from tea. This was followed by an experiment on separation techniques which included thin layer and gas chromatography along with distillation and recrystallation. The next experiment was a simple Grignard reaction. The only difference from the usual sort of synthetic experiment was that each student was asked to hand in a gas chromatograph of his product. A Perkin-Elmer 154 Vapor Fractometer is a standard feature of our or-
' Ross, J., J. CHEM.EDUC.,43, 112 (1966). ' SMITH,R.B., J. CHEM.E ~ u c .46,148 , (1967).
BAT~INO, R.,J. CAEM.EDUC.,43.281 (1966). 'Several alcohols were found to present di5culty for the average student: allyl, henzyl, oyclohexyl, and h c t a o o l . 8
ganic lab; each student is instructed in its use, and all students are expected to know how to operate the instrument. I n this experiment, a very easy method of collecting traces is to have each student inject a sample and then sign his name a t the starting point. When all have run their sample, the chart can be unrolled and the chromatographs compared. The comparison very nicely emphasized for the students the variability in products and product ratio in a seemingly simple textbook reaction. A week before the completion of the last prescribed experiment, each student was given 200 grams of a simple aliphatic alcohol4 and asked to submit five gram samples of 3 compounds of a known purity prepared from the alcohol. The only requirement was that each student choose one compound from each of the categories below: 1
2
Ketone Aldehyde Acid
Alkyl halide Hydrocarbon Amine
3 Anhydride Amide Ester using acid derived from alcohol.
The compounds were to he submitted with extensive identifying constants, i.e., melting point, boiling point, indication of purity by gas-liquid chromatography or thin-layer chromatography, a 4 ir spectrum, and procedure for preparation. The identifying data could be recorded in the laboratory notebook. After satisfactorily completing this amount of work in the lahoratory the student had finished the basic lab and could receive no less than a grade of C for the lahoratory part of the course. Since there was no laboratory manual for the course, the student was forced to go to the library to find an experiment. However, most of the alcohols are not specifically listed in standard lahoratory manuals. Therefore, the student had to modify an existing experiment or design a specific experiment for his individual alcohol. I n short, a student had to think about what he was doing in the lahoratory. To aid the student as much as possihle to do this, a large numher of lahoratory texts and standard reference works on organic synthesis were ~ u ont reserve in the lihrarv. I n addition. a brief lecture was given along with a mimeographed handout listing or describing briefly the various reference works and the students were urged to use them. I n addition to actually performing the experiment, each student was asked to keep a detailed lahoratory notebook, A numher of criteria were suggested for keeping the laboratory notebook as much like a standard research notebook as possihle. I t was emphasized that detailed observation and reports of results were necessary, with references and procedures clearly stated. Volume 45, Number 4, April 1968
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The notebooks were graded a t the end of the semester. It has been our experience that very few students realize the purpose of and the need for keeping an accurate record of an experiment. We felt that until the student gained some skill and ability in the laboratory each experimental procedure ought to be checked by an instructor. Therefore, each student was asked to submit a plan of the experiment to his instructor a minimum of three days before heplauned to carry out the experiment. The experiment plan consisted of: List of chemicals and quantities needed Approximate duration of experiment Possible hazards and safeguards A brief description of the experimental procedure
The plan was reviewed and in most cases approved with only a minor suggestion or two. If the plan was approved, the chemicals list was signed and the student could then obtain the necessary chemicals from the stockroom. If the plan was rejected, reasons were given and alternate suggestions were offered. All were invited and encouraged to consult with either of the two instructors about any given experimental plan and procedures. We realized that the experiments that students were likely to devise would not be "cut and dried," requiring exactly a lab period to complete. Therefore, beginning with the fifth week of the semester the laboratory was opened from 9 to 5, five days a week. The one provision was that one of the two instructors had to be in his office a t the time. The instructor's offices a t Cortland are adjacent to the student laboratory, so that an instructor is immediately available in case of emergency. We periodically went through the laboratory checking student setups and procedures. We would also recommend that a t least two students be in the laboratory when work is going on. The instructors divided the week in half and agreed to be responsible for one half of each week. Each of us was available for consultation any time during his half of the week. There were no serious accidents in the lab. The only accidents were the usual complement of cuts and minor burns. After the student had completed the basic part of the lab, he could do any of the following to earn a higher grade: Prepare mare compounds from each group Use mare complicrtted synthetic techniques Prepare compounds not listed in the categories from his alcohol Begin and carry out rt simple individual project Attempt to prepare compounds not previously reported in the literature
I n practice all of these paths to glory were taken. The choice was up to the student. Most exercised an option and proceeded on their own. In actual practice we have found that our grading criteria had to be applied rather loosely. Often a student might do a great deal of work and not be able to prepare a specific compound. We felt that at least part of this work should be recognized, and modified grades accordingly. In addition, a well-organized laboratory
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notebook was a large plus factor for the student. Most students managed to get a t least a C in the laboratory. The smallest number of compounds submitted was one, the largest number submitted was eight, and several students began independent projects. The second semester of the laboratory was designed primarily to acquaint the students with a variety of reactions. Therefore we had only one prescribed experiment, dealing with stereoisomerism. Then we handed out a list of 35 name reactions and we asked our students to run a t least five of these of his choice. After this each student received one qualitative organic analysis unknown. The unknown was a simple one containing a t most two functional groups. Students were given basic instructions in the laboratory in methods of identifying unknowns. All students had easy access to an Infracord to aid in determination of functional groups present. Spectral methods used for structure determinations were discussed in the lectures for the course. When the student had done the prescribed experiment, the five reactions and one unknown, he had reached the C level. He then had similar options as in the first semester. He could do any of the following to earn a higher grade: Try more reactions Try more complicated techniques Attempt another unknown Work on an independent project
We feel that there were two major advantages of this type of laboratory; it generated tremendous interest and enthusiasm among the better students, and all students began realizing that organic chemistry is very often not what a cookbook type laboratory manual leads one to believe. They discovered that reactions do not always work smoothly, yields are not always good, experiments do take longer than 3 hr, what works on paper may not work in a flask, and a laboratory does not have to be dull and repetitive. The first reaction of our students to the announcement of the new laboratory course was mild hysteria. There were no direct~onsto follow!! Most students eventually calmed down and began working well. By the end of the semester their comments were generally very favorable. Some ran through the second semester in only a few lab periods in order to begin a project, and others were fascinated with freedom and made a large number and variety of compounds or tried many reactions. Very few failed to do work beyond the C. Most liked the idea of choosing their own experiments and working a t their own pace. Most gripes concerned difficulties arising from laboratory logistics. We claim no great improvement in the level of competence of our students in the laboratory, nor any great pedagogical advantage to our lab setup. There may in fact be advantages to this type of system, but in the absence of controlled experiment, we cannot say. However, we do claim that this type of course is more interesting, exciting, and challenging for both the instructor and student. It tends to be more work, but is also more fun.
