OBJECTIVES of the FIRST COURSE in ORGANIC CHEMISTRY' R. Q BREWSTER University of Kansas, Lawrence, Kansas
A
S TEACHERS of organic chemistry we are likely to consider ourselves as chemists, rather than educators, with but one objective, vie., the thorough presentation of a selected subject matter
with the insistence that the students learn as much of it as possible. The statement that education is sometimes mistaken for recreation seldom applies to us. Whatever our objective, almost never do we sacrifice TPresented before the Division of Chemical at the the content of our course for its attainment. We hold ninety-fifth meeting of the A. C. S., Dallas, Texas, April 19, 1938. that the mastery of the subject is in itself the primary
aim. However, lest we forget our pedagogy entirely, let us try to divide this larger task into smaller parts which may be attained individually. In addition we should determine the object for which the students have enrolled in our courses. In most colleges and universities only a few of these students plan to be chemists. The vast majority of them are studying organic chemistry because of its relation to medicine, pharmacy, dietetics, bacteriology, and the like. In the larger institutions students are divided accordmg to their own vocational plans though it is the belief of the author that such division is more for the proper selection of the subject matter to he studied by each group rather than for the attainment of an entirely different set of ohjectives. It is quite true that the student of biology is less interested i n methods of synthesis and theories of molecular rearrangement than he who expects to he a chemist; yet the biologist should know some of the syntheses and the most outstanding part of the theories. For such students intensity of training along these lines may well be replaced in part by a broader view of the subject matter through the inclusion of topics of more direct connection with his future field of work. Hence with some modifications in the "intensity factor" the objectives discussed below may apply to all students regardless of their ultimate aims. 1.
STRUCTURAL
FORMULAS, NOMENCLATURE, .AND ISOMERISM
Since the suhject assigned has to do with the first course in organic chemistry, i t is assumed that other courses may follow in which the more elaborate parts of the suhject can be considered, and we would therefore state as the first objective of this study the mastery of structural formulas, nomenclature, and isomerism. Structural formulas are essential to the understanding of organic chemistry and students must learn to write them accurately and rapidly. The names of simple compounds should be readily translated into the structural formulas and vice versa. The Geneva system of nomenclature as well as the commch names of compounds must he studied, and in the author's experience the former is the more rapidly acquired. Students should see also that in each family of compounds the first member of the family may he considered as the parent of the following members. For example, paraffins may he named as derivatives of methane, olefines of ethylene, and alcohols of methanol (carbinols). Isomerism is an interesting phase of chemistry which is here met for the first time, and much fascination is attached to writing the structural formulas for all possible isomers of a certain empirical formula. Particularly is this true if beginning students may have access to Richter and Beilstein in order to determine how many of these isomers are actually known. The time devoted to the mastery of these fundamental ideas of formulas, nomenclature, and isomerism a t the beginning of the course is well spent, as this knowledge is of great benefit in the study of each successive group of compounds.
2. CLASSIFICATION Our second objective should be to teach students that carbon compounds may be classified into a comparatively few families each of which has its own type formula and characteristic chemical behavior. No branch of science excels organic chemistry in the beauty of its organization. The typical properties of the more common members of each family must he learned and the essential characteristics of other members of any homologous series may then he deduced by ana10gy.~ Such a study of the chemical nature of one group of substances after another may easily become very irksome and the beauty of the subject buried under an avalanche of chemical reactions. However, while the student is mastering these all-important reactions, the instructor can well set himself to the task of avoiding monotony and enriching the suhject with many illustrations of the use of these processes in the industrial and scientific life of our time. Early in the course advantage may he taken of the study of the olefines to show their relation to such substances as the polyene pigments; a point which never fails to gain an appreciative response from students. Thus while the more prosaic list of chemical equations is being learned, the subject increasingly assumes interest and importance and manv comnlex comaounds lose their intricacies hv virtue of-their icing cataloged in the student's mind & substances of multiple function, belonging to more than one family and showing the properties of each.
3. FUNDAMENTAL THEORIES The facts of chemistry should not be detached from its theories, and in the first course in organic chemistry there is ample opportunity'to build upon the theories studied in preceding semesters as well as to introduce new concepts. Along with the accumulation of the large amount of information which the study of the subject has to offer, the student should acquire a good training in theory. Ideas as to-the mechanism of a process are often quite as important a matter for consideration as the process itself, and such ideas should be introduced whenever they may be used to explain the facts. Why, for example, does the aldol condensation take place a t the carbon atom adjacent to the CO group? The theory of tautomerism provides an explanation for this as well as-certain other properties of aldehydes and ketones. Of course there is a limit to the amount which can be accomplished in one semester, and the theoretical ideas as well as the factual content of the course must be a matter of selection. Our intention here should be to lay the foundation for later study. Optical activity, geometrical isomerism, tautomerism of the nitro paraffins, and so forth, all help to make up these fundamental theories, and it is well to present them as ideas which arose out of logical reasoning from experimental observations. Perhaps other teachers share the author's satisfaction in pointing out that a The author readily admits that the principle of homology cannot be extended too far, though few exceptions to it would arise in the first course.
although the physicist has demonstrated the existence of tetrahedral molecules or the flat disc of the benzene ring, the organic chemist had already arrived a t those couclusions. 4. CORRELATION WITH OTHER S W P C T S Most of the old masters were proficient in the other sciences as well as in chemistry. Our present-day specialization into certain subjects has its advantages, yet the interrelation of various phases of science is just as important as ever. It is our duty, as well as our privilege, to make as many applications of chemical facts to other fields as is possible in the time a t our disposal. Students of chemisw take more interest in their German, mathematics, physics, bacteriology, and so forth, when they see how closely these subjects are allied to chemistry. The bacterial liquefaction of gelatin becomes more meaningful when it is understood to be the hydrolysis of a protein a t the acid amide groups. The number of such applications is quite large, indeed, and many subjects may be included. The author will always remember one of his earliest research preparations as being of unusual importance because the research director referred to it as the "ausgangs-material." Incidentally, the study of chemical German thereby received a new impetus. The study of the optical and electrical properties of carbon compounds naturally emphasizes the connection. with physics. When time is so limited and the field so broad nothing can be done in the first course in organic chemistry with the subject of dipole moments, yet it might be mentioned that polarization measurements show that ethers form an obtuse angle at the oxygen and are not straight line molecules. Such illustrations need take only a little time, but they are eminently worth-while in demonstrating that our subject is a part of the whole of science and not only is benefited by other branches but is in turn a benefit to others. A knowledge of organic chemistry is particularly important to students of biology, medicine, pharmacy, dietetics, agriculture, and many otrer sciences. It will help even a physicist. 5. INTRODUCTION TO CHEMICAL LITERATURE We are teaching organic chemise-not a textbook. The subject itself is far larger than any one book and in fact the text is an extreme condensation of a very large number of articles in the journals. So great a wealth of literature is available for study and is so important to an understanding of the subject that the student should begin to be familiar with i t early in his training. At the outset of the course in the study of the paraflin and olefine hydrocarbons references can well be given to articles in the industrial journals upon the petroleum industry. The separation of bromine from sea water and its conversion to ethylene dibromide3is especially interesting to students. The intensive classroom study of any family of substances is enriched by these library references and the student is supplied with a breadth a STEWART, L. C., Ind. Eng. Chem., 26,361 (1934).
of view which takes the subject out of the classroom and puts it into a world of scientific affairs. Although the student may as yet have only a limited knowledge of languages, the foreign journals need not be omitted. In fact it is well to point out that science, like music and paintine, is a world-wide undertakine. Memorial lectures, sucuh as those in the Journal of-the Chemical Society (London) upon the lives and works of eminent chemists as well as pictures of the men and their laboratories do much to convey to the student the internationalism of science. 6. COMMERCIAL DEVELOPMENT Organic chemistry is very much alive, not only in a purely scientific sense but also in itscommercial applications. Many substances which until recently were of use only for instructional purposes in the classroom and laboratory have been adapted to economic needs, and their production is now measured in tons rather than in grams. This is well illustrated by the recent advances in the aliphatic series. Sometimes chemical reactions which failed under ordinary laboratory conditions have been carried on successfully on an industrial scale under the influence of proper catalysts and a t sufficiently high temperatures and pressures. Ethylene and acetylene as well as other hydrocarbons have thus reached important places as source materials for the preparation of large quantities of numerous substances. Surely the last fifteen years has not witnessed the completion of such developments and many more will be made in the future. Students should have a view of organic chemistry as a field with ever-widening horizons. 7. LABORATORY .. OBlECTIVES Laboratory 'experimentation is the true method of studying a science. The results of these experiments are recorded in the books and chemical journals which students may read, but not all of the knowledge of a subject which one obtains should be derived from the literature. Some of i t should be aequired a t the fountain source in the laboratory. The work here should be partly preparations, as each student will need to know how to prepare certain typical compounds, and partly test-tube &dies of the^ propertie; of the substance which he has made, as well as many others. The objective in the laboratory should be to acquire orderliness and skill in experimentation, whether it be a matter of making preparations or studying the properties of substances in test-tubes. 8. DEVELOPMENT OF THE STUDENT'S REASONING POWER Development of one's reasoning power is the ultimate objective of all education, and we set it as the last in this list. Few subjects are better adapted to this purpose than ours. A structural formula is assigned to a substance because of its observed properties, and after the student has solved a few problems in which the structural formula of a compound is to be determined from its analysis, molar weight data and chemical behavior, he concludes that the deduction of the formula is quite a logical process. In the solution of such a
problem he has used information which he obtained in general chemistry and quantitative analysis as well as in organic chemistry. Problems in the synthesis of one compound from another also develop this reasoning power and impress upon the student's mind the inter-
relation of various families of substances. The proof of the identity of a qualitative "unknown," if it be one of a selected list of materials, is not too difficult for our first course and is an excellent means toward the same goal.
