JOURNAL OF CHEMICAL EDUCATION
ORGANIC QUALITATIVE ANALYSIS AT THE GRADUATE AND UNDERGRADUATE LEVELS DOUGLAS 1. HENNESSY Fordham University, New York, New York
TEEadvantages which accrue t o the student of organic chemistry as a result of taking the course in qualitative organic analysis have been clearly and fully stated by Professors Huntress and Shriner in their papers on this subject which have appeared in the JOURNAL OF CHEMICAL EDUCATION in 1930 and in 1941. No thoughtful teacher of organic chemistry having read these papers could fail to realize the training value in such a course. Actually it would seem that this course is well nigh indispensable, especially if students are being prepared for graduate study in organic chemistry. None the less, many departments of chemistry still do not offera course in qualitative organic analysis. There are various reasons which may be given for this, among which are lack of appreciation of the benefits involved, apparently limited facilities in the laboratory or library, seeming shortage of teaching personnel or perhaps just plain inertia. It is my hope that the remarks which follow will stimulate those in whose departments qualitative organic analysis is not now being offered so that they will do something constructive about this lack of a valuable discipline in the molding of organic chemists for whose early training they may be partly responsible. I thought that if I were to present a brief history of some of my own experiences, just after this course was introduced in our department, together with certain observations which I have made from time to time in conducting this course, I might thereby encourage a feelmg of confidence in the intrinsic values of the course which will, I trust, shi,ne throughin spite of my fumbling efforts. I n our department, the course in qualitatiee organic analysis was initiated as an elective graduate course about eleven years ago with some half-dozen students participating. With obvious misgivings on his part, I was placed in charge of this course by the chairman of the department in the following year, al-
though I had not taken such a course in my own undergraduate or graduate career. I found those first two years highly instructive. It became apparent to us a t a very early stage that we should somehow make this course available to the senior organic chemistry majors in the college. This meant an increase in enrollment from 6 to 24. The students could no longer work in odd corners, so we appropriated some empty lockers in a freshman laboratory, had some extra shelves built along one wall for the test substances, solvents, and classification reagents whose use was required in the method of systematic identification of Shriner and Fuson. The more expensive reaghnnts for the preparation of derivatives were retained in the custody of the instructor so as to discourage the well-known acquisitiveness of the Ph.D. candidates who seem to find that everything that is not nailed down is essential to the solution of their problems. We were fortunate to have most of the reference hooks in our departmental library and those few which we did not have were readily acquired. Ovens, balances, refractometer, and a polarimeter were in the building. However, since these were used in other laboratory courses, the resulting feud did not lead to departmental harmony. I would advise on the basis of this experience that separate equipment be acquired, even though gradually, so that the sole responsibility for its care rests on the instructor in this one course. There was no unusual glassware required, so that installing the material for 30 students involved no great expense. We very soon realized that individual sets of reagents were a practical necessity both for preventing contamination and for insuring a laboratory which did not resemble Grand Central Station a t 5:30 with the long queues of students a t the reagent bottles and the great milling about. The 92 test substances were arranged alphabetically in duplicate 4-02.
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liquid or solid bottlea with varnished labels. On each liquid bottle a simple device made of copper wire was attached as a holder for a medicine dropper. Qualitative reagents or materials required for preparing them, as described in other sources such as Kamm or Mulliken, were available either in the main stock room or in the laboratory stock room. It was no great difficulty to get under way, having as we did a flourishing graduate organic division in which advanced preparations and research were being conducted. Immediately a t hand were most of our needs in the way of chemicals. Even so, we did have to purchase quite a few chemicals especially for use as unknowns which in most instances were obtained in 100-g. lots. The chairman of the department was unhappy about this fairly large original order until I explained the need of having compounds whose purity was unquestionable and which could be held out of general stock. Furthermore, I assured him that the order for the subsequent years would be much smaller unless the students enrolled in the course increased in number, which they eventually did after first decreasing during the war. Last year 54 graduate and undergraduate students took this course. Now perhaps there are those departments in the smaller colleges, which in organic chemistry give the usual undergraduate cou-se with some advance laboratory preparation or perhaps even a thesis for seniors, who might wish to introduce qualitative organic analysis but who have been reluctant to do so because of the extra strain on the budget. I believe if funds are really limited, a gradual introduction of the course over a three-year period could be a practical means of r e maining within budget limitations in such instances. The first year, for example, the chemicals for the classification reactions might be purchased on the basis of a fiveyear requirement and immediately put to use in semimicro tests on materials prepared in the elementary and advanced laboratory courses. At the same time, a beginning could be made ou filliig library needs. The next year the reagents for the preparation of derivatives could be obtained and the use of these could be introduced into the laboratory preparation courses. The library needs could be further expanded a t this time and a polarimeter and refractometer would certainly be worth-while acquisitions. The test substances are available in every laboratory so that a t the beginning of the third year a full-blown course in qualitative organic analysis should bloom. Who is to teach this course, you may ask. Can it be given by one who has never taken such a course? There is no doubt that i t would be preferable for the prospective teacher to have formally experienced a good course in qualitative organic analysis. This is certainly not essential, however, provided the teacher is well versed in the practical aspects of organic chemistry and can understand the full significance of the analytical procedures and their theoretical basis in such books as are used and referred to in the course. It is essential, if the objectives of the course are to be
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attained, that the teacher be an enthusiastic proponent of this method of training. One question of pedagogical significance with which we had to contend and on which each teachermust make a decision has to do with the proportioning of available time to be spent on group instruction for explaining procedures, the use of the library, and the working of problems on the one hand and time spent on actual laboratory work on the other. This ratio will depend largely on the previous training of the students, but it must be kept in mind that this is primarily a laboratory course accompanied by literature search and it must be kept so if the objectives of this course are to be realized. In our experience at least 75 per cent of the time available in the first term should be spent in the laboratory and 90 per cent in the second term, at which time the identification of unknowns is mostly accomplished. Some students find it necessary to put in extra time in order to keep up with the rest of the class, and this is as it should be. That phase of the course from which most of the training arises is obviously the actual proof of the identity of unknowns. One aspect of this course which requires considerable thought is the matter of the nature of the unknowns, the number of unknowns, and the manner of evaluating the students when, as we know, the problems posed by different unknowns may be quite different in their complexity. Of the hundreds of thousands of organic compounds reported in the literature, those which are qualified to serve as unknowns are limited by availability, cost, stability, purity, and fitness for the general scheme of identification. Inadvertently we have ordered commercial samples of recently developed compounds and of newly available substances from various manufacturers only to realize, after some hapless student had worked himself to a frazzle, that the substance did not lend itself to identification by the means ordinarily employed in the schemes of qualitative organic analysis. Either they could not be adequately classified or there was a lack of derivatives or both. I think it can be generally conceded that there are many compounds which cannot be positively identified without quantitative analysis, a t least not in the time alloted. What does one do when a student believing he has exhausted all possible resources in his attempts to prove the identity of an unknown still has not succeeded? Well, we hold a conference in which the student presents his laboratory data, the literature to which he has referred, the reasoning he has employed, his tentative conclusions, and whatever else he can offerto prove that he has done a yeoman's job but alas! science has let him down. Our response to this usually solemn recital might be to tell him to redistill or recrystallize his unknown and then to check his physical data or his elementary analysis or his solubility classification or perhaps even his classification reactions. If he has done a generally poor job, we make him repeat the whole analysis. We might suggest some additional references if the usual sources have not been satisfactory for the
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preparation of derivatives. Of course, this service is not gratis, and, depending upon the difficulty of the unknown, and upon the independent effort which the student has made before asking for the consultation, we may tax him from 10 to 30 per cent. This system is one on which my conscience is tender and I would appreciate knowing the procedure which others adopt when failure to prove the identity of an unknown is the result of a simple error of omission or commission which timely advice can rectify. More than once I have had to tell the student that I was unable to make any constructive suggestion since the substance which he had been given as an unknown had proved to be unresponsive to any reasonable group of tests which ordinarily might be employed. I might then say, as I dld recently, that the substance in question is used as a ntbber accelerator. With this information the student was able to make a positive identification. I don't feel that in such a case the disclosure of an application of the compound after the student has satisfied all ordinary requirements is acting against the purposes of the course. In the industrial field this type of information usually accompanies a sample for analysis. I have in rare instances been forced to conclude that in spite of our fairly liberal regulations, the student has succumbed to temptations usually as the course mas drawing t o a close and he began to feel the pressure of time. A feu, transgressions which I have observedand I realize there may have been others that I missedhave been the result of the inability of the student to prepare more than one deriva.tive. Since we require two in nearly all cases, the student may place a handy crystalline material in a sample tube and hand it in labeled as a derivative. A check of the melting point uncovers the dark deed. Here is another problem. Shall we consider this student to be unreliable as a scientist, and so take such steps as would exclude him from the field of chemistry, or is it enough t o vigorously impress him with the unmoral nature of faking scientific evidence and the serious consequences to himself and others which may result from such an act? Probably it is best to consider each case on its own merits or lack thereof. To the best of my knowledge, the number of general unknowns whose identiffcation is required actually varies from 4 to 16 in different schools where the course in qualitative organic analysis is given. Now, of course there is little value in requiring the identification of all or even the majority of a very large number of unknowns if these unknowns are particularly easy or if there are many duplications of unknowns among the
JOURNAL OF CHEMICAL EDUCATION
different students or if they are not changed from year t o year or if the students have access to a stock room in which many of the unknowns are maintained as stock. I t is perfectly obvious that any or all of these conditions would permit identification of unknowns with only partial and even negligible recourse t o those procedures in whose use precisely lies the discipline and training for which this course is given. On the other hand, although four unknowns are admittedly a low minimum, it is sometimes practically very difficult to demand more of students in a liberal arts college when their senior program may be very heavy, especially if the dean is adamant in such matters. Probably a reasonable number of unknowns for the great majority of schools which would offer this course would come very close to the suggestion of Shriner for six single unknowns and two mixtures. My h a 1 comments are addressed to the subject of the proper place in the curriculum for the course in qualitative organic analysis. At present we require this course for organic chemistry majors in their senior year. It is also a required course for those students coming from other colleges a t which this course is not offered. At present, graduate credit is given. Eventually it will become a prerequisite if it is generally adopted in undergraduate curricula. No identification work as such is offered in our elementary organic courses, although in certain experiments we have added classification reactions and preparation of typical derivatives for what would be otherwise limited to preparative work. The graduate and undergraduate students take the same course. Generally the graduate students complete their unknowns earlier. I attribute this to the extra time which they spend and to their greater familiarity with and facility in the use of the literature. Next year, we are going to demand of the graduate student the identification of a greater number of unknowns. We intend to step up the requirements for the seniors as well, although to a lesser extent. By distributing the unknowns at the 4th week of the 30-week (4-credit) course instead of at the 11th week, we are hopeful that the greater number of unknowns can be solved in the allotted time. In closing this paper, I want to leave this final thought with you, that since qualitative organic chemistry is a relatively recent arrival in the chemistry curriculum of many schools, there is as yet no widespread acceptance or even recognition of minimum standards. In this respect alone, a vast and unexplored area exists, which requires extensive discussion and ultimately careful delineation.
