A novel philosophy for a first course in organic chemistry

A Novel Philosophy for a First Course in Organic Chemistry. Melvin S. Newman. The Ohio State University. Columbus. OH 43210. The teaching of a ...
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A Novel Philosophy for a First Course in Organic Chemistry Melvin S. Newman The Ohio State University. Columbus. OH 43210

The teaching of a three-quarter (or two-semester) course in beginning organic chemistry presents problems. Some students (often the majority) will not take any more chemistry whereas others will major in chemistry. Should both types be given the same material? In my opinion, no. In this article I present my ideas about teaching a class of non-chemistry majors which resulted from two sears of experience with the new approach. In formulating my philosophy of teaching such a group I thought much about what I hoped the students would remember many years after the completion of the course. Certainlv. most of the factual material would be foreotten. I conci"ded that they should recall the importance of iesearch, what research has meant to the welfare of this country and to the world, and what may he expected of research in the future. I t is of ereat importance that the educated man and woman of the future truly appreciate the value of research. In the average person there is too much attention paid to the concept of "ivory tower" research. With the above objective in mind I decided that the traditional way of teaching organic left much to be desired. Too often organic is referred to by students as "a memory course, ugh." In my opening lecture I based my thoughts on emphasizing the character of research by stating that research workers not onlv needed to know manv facts but also this knowledge needld to be available quickiy. Speed in recalling facts comes mainly through the expenditure of constant effort. T o illustrate this point I talked about the great musician or great athlete. Such persons become great not only through natural ability hut also by great effort: witness the hours of practice at the instrument or on the field, practice which must continue throughout a career. So great researchers constantly practice by increasing the number of facts and the methods of research peculiar to their field(s). T o illustrate my approach I will give two specific examples.

1. Saturated Hydrocarbons Most organic courses start with paraffins, C,H2,+2. For example. methane. ethane. propane. butane. isohutane. etc. ~ a r l i i my n course1 stated thatman; years ago the ~ m e i i c a n Petroleum Institute (API, an organization hacked by many of the large oil companies) supported the research of Professor C. E. Boord of Ohio State. He was to synthesize about two gallons each of the 18 isomeric octanes. At this point I showed n-octane and 2-methylheptane and asked the students to acceot the fact that there were 18 comoounds of formula c ~ H and ; ~ that I would explain later. he cost of research made i t likely that each gallon might cost $5,000. Why should the API be anxious to pay such a price for gasoline? The answer was that the oil companies wanted to know which of the 18 isomers of octane would be best in engine tests and which would he helped most by the addition of lead tetraethyl, a catalyst useful in increasing the octane number of gasoline (still listed on most gasoline pumps). With this knowledge the oil companies felt that they could improve their refining and manufacturing processes and produce better grades of gasoline. Here I emphasized the importance of the effect of structure on some property. For example, if a certain com380

Journal of Chemical Education

pound had some biological activity what effect on this activitv would a change in s t ~ c t u r make? e This type of question is of fundamental importance in the search for better medicines and agriculturalchemicals, to name only two areas, and was referred to often in later lectures. I now demonstrated on the blackboard how to draw formulas of the 18 isomers of octane. At this point I announced that one question on the final examination would be to write out the 18 isomers. However, students who miaht take more than two minutes to write down the carhon skeletons would he penalized in that they woukd not have as much time for the rest of the examination. Furthermore, the grading would he such that if there were three errors the answer would be graded zero! I then ureed the students to work this out and time themselves on more than one occasion. This meant they had to develon. a svstematic method. I believe the educational . merit of this exrrcise and its emphasis on speed is imp~~rt;int. Having the 18 isomers 1 then took up thequestion of nomenclature. The students could readilysee thk need for naming, and this need was emphasized as needed later in the course. The possibility of opGcal isomers was not mentioned at this point, hut it was dealt with later. I then pointed out that to prepare the compounds methods of synthesis had to be worked out. This aspect served as nrenaration for the discussion of certain svnthetic methods iater in the course. I did not give the syntheses of all 18 compounds but stressed the importance of synthesis to organic chemical research. Examples of the synthesis of some octanes were given in later lectures involving various functions. This aspect can be developed to show how research done by workers who had no thought of making octanes could be used by persons trying to make octanes. Thus, the use of research of all types can be emphasized. The net result of Professor Boord's reiearch was to provide the 18 isomeric octanes in sufficient amounts that their evaluation as gasoline could be made. The testing showed that branched octane isomers made considerably better gasoline than almost straight chain isomers. Hence. the oil comoanies were able to improve the octane value df the gasoline'they produced by changing the practices in convertine crude oil into easoline. In turn. improved octane values of g&olines made f i r improvement's in-the design of internal combustion engines. 2. Unsaturated Hydrocarbons

One topic covered under olefin chemistry is cis, trans isomerism. I approached this topic as follows. Many years ago chemists were interested in determinine the structure of natural products, substances found in, and isolated from, manv sources. One such source was the sao of rubber trees. In trying tu discover the structurr of n h t a r , chemisti S~KIIIfound that it could not be crystallized or distilled. It belungs toa class of pulymeric materials. Howe\,er, on heating natural rubher in the absence of air (a process called "crackinr"~ii voletile substance, isoprene



was obtained in high yield. After having proved the structure

of isoprene (different lecturers may spend different amounts of trine on this asoeot . 1.. chemisu wondered if sou wuld r e t ~ ~ r m ruhher from isoprene. Accordingly, worker; tried to do this. Some were successful and got a product quite similar to natural ruhher. However, others got a polymer that had no flexihilitv and was m i t e stiff, namely, gutta percha. Since both rul,her and gut& percha were i o r k l from the same starting material, isoprene, why jhuuld substances of such widely different nronerties he ohtdined? I then showed that the an-~--swer lies in thk stereochemistry: ruhher has an all cis chain and gutta percha all trans. I think this approach to cis, trans isomerism is preferable to the conventional one which often uses cis- and tram-2-hutene to illustrate the point. Starting from this point one can now show how the whole field of synthetic ruhher developed since research workers tried many varieties of isoprene. For example, if the methyl arouo . . in isoprene were replaced by a chlorine (to give 2chloro-1,3-t1titadiene) or hydrogen (to give 1,3-butadiene, much lew expensive than isoprene! ruhhers with p r ~ w r t i e s similar to, hut different from, natural ruhher could he synthesized. This research was developed mostly in Germany whose leaders realized that in the event of war Germany would he cut off from all supplies of natural ruhher. In the USA comparatively little research in synthetic ruhher was done. After all, did we not have command of the seas and full access to all the natural ruhher we wanted? And then came Pearl Harbor! Overnight, the seas were not free! This event triggered ~



a vast amount of synthetic ruhher research in this country because of the overall imoortance of ruhher in peace and in war. The above two examples can he developed by showing how many of the facts one learns in a course in organic chemistry are gained because of trying to answer relatively simple questions. This research aspect is very interesting to students. While lecturing on the above two topics the attention paid by the students was pleasant to behold. I could go on to illustrate the research point of view in teaching a beginning course, hut I will not do so. After all, the individual teacher can prepare similar lectures by spending some time in thought and in the lihrarv. Manv different areas are susceptible ro this philosophical iesearch approach rfor example, the use of 'Tin tracing metaholiim, proteins, carbohydrates). I suspect that if this rrnph,~sison the impmunw of resrarch were generally used in reaching organic chemistry, rhe educated student would carrv thruuchuut liie a . Droner . appreciation of the importance of research, not only in chemistry hut also in other areas. Conclusion

I might add that I was amazed by the number of students who came to my office during the next quarter to state how much they had enjoyed this course and that they had gained an appreciation of the value of chemical research to mankind.

Volume 59

Number 5

May 1982