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PERSPECTIVES IN ORGANIC CHEMISTRY INSTRUCTION' JACOB 6. SHAREFKIN Brooklyn Colleg.e, Brooklyn, New York
ORGANIC chemistry is considered by students to be one of the most difficult courses in the chemistry curriculum. For the student the troublesome areas in this subject are the new and large vocabulary, the volume of subject matter, the unfamiliar techniques and equipment of the organic laboratory, and the solution of exercises in organic synthesis. Among the difficulties that bedevil the beginner in this field are the new language and structural formulas which must be learned to understand the most elementary concepts. This task becomes even more Herculean when three separate systems of nomenclature are presented for each homologous series, e. g., the Geneva or I.U.C., common, and derived names. Thus the molecule CH&H = CHCH3 is designated by these three systems as butene-2, beta butylene, and s-dimethylethylene. It is therefore not surprising that student failures in oreanic chemistrv examinations frequently arise from ignorance of a particular name for a given compound. For elementary students it is recommended that only the systematic I.U.C. and industrially important common names be stressed to the exclusion of the derived names which are no longer important for research or industry. It is likewise important to present the student with a concise summary of the I.U.C. rules for all homologous series a t the beginning of the course. Another major difficulty for the novice is the volume of subject matter in current organic chemistry textbooks, which have recently become larger and more detailed. In these books little attention is given to the beginner who must orient himself in a new and complex field. The vast body of information in the textbook, coupled with the rapid pace of instruction, makes it di5cult for an average student to digest and assimilate his assignments. A successful professor with a twentyfive year record of experience in this subject found that his average students were able to master forty per cent of the course content. He also learned that there was no uniformity in the forty per cent of the subject matter that his students had learned and concluded that there was considerable variation in the students' estimate of the essential material of the course. The fact that the average student reproduces a variable fraction of the subject matter places the responsibility for outlming the course and emphasizing important reactions with the lecturer. Inasmuch as the lecturing professor must also integrate theory, discuss
ideas critically, and inspire his students, the lecture hour becomes a race in which the student strives desperately to transcribe the lecture and listen at the same time. Some of the pitfalls in this situation may be avoided by supplying the student with a set of all the essential equations numbered consecutively. By slipsheeting the pages containing these numbered reactions between the blank pages of the lecture notebook the student is relieved of the chore of copying equations and is thereby enabled to make notes on the critical comments of the lecturer. The lecturer refers to the reactions by number and uses the time, which would otherwise be spent in writing equations on the blackboard, more profitably for evaluation and discussion of the reactions. The laboratory work in organic chemistry, following general chemistry and qualitative analysis, is the first ex~eriencefor the student in settine UD laree-scale glass equipment and handling combustible chemicals. These tasks usually occupy him so completely that the observation of the reaction for significant chemical changes and the correlation of these with theory are forgotten. The student is not aided in this important objective by current organic laboratory manuals which feature theoretical topics such as distillation, crystallization, etc., and precise directions for performing experiments. In addition to these topics a balanced laboratory manual should point out to the inexperienced student the signs of reaction which are significant to the chemist. To give the student an appreciation of the chemistry of reactions and proper training in observation it is helpful to supply printed material that explains the purpose of each reagent and operation and also points out the observable changes which are the signs of reaction. This aspect of the laboratory work is further emphasized by requiring the student's final laboratory report to contain a detailed flow sheet for the experiment. Flow sheets are particularly important in organic chemistry because the time required to complete a synthesis and isolate the pure product limits the student to lifteen preparations per semester. Each preparation must therefore be exploited to illustrate as many reactions as possible and it is here that the signs of reaction become most significant. I n the preparation of mandelic acid from the liquid benzaldehyde the first product is a solid bisulfite addition compound. The latter is treated with potassium cyanide to form liquid mandelonitrile which is then hydrolyzed to the This paper was presented before the Division of Chemical Education a t the 112th meeting of the American Chemical soEd mandelic acid. It is common practice to assign problems involving Society, New York City, September, 1947. ~~~~~
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the synthesis of complex organic molecular structures from relatively simple compounds. Yet textbooks of organic chemistry offerno systematic instruction in this phase of the work. The solution of such problems without any written reference material requires s high order of genius from a beginning student. The \vriter has prepared a series of solved exercises2 of graded Q ~ J. G,, U ~ Ein Y . Crowell Go., New York, 1947.
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difficulty for each homologous series. If these are mastered by the student it is possible to assign more challenging problems. The use of the instructional devices enumerated above suffersfrom the drawback of multiplying secondary reference sources for the student. They are considered to be temporary expedients by the writer who earnestly hopes that future textbooks and laboratory manuals chemistry include this instruc~~ ~ in ~organic ~ ~ ~ ,will ~ tional material.
