Small-Scale Organic Chemistry in Retrospect

John T. Stodc University of Connecticut, Storrs. CT 06269

A notable feature of current teaching in the organic lah- oratory is the reawakening of interest in small-scale tech- niques ( I ) . I t is gratifying to note that recent publications (2-4) draw attention to modern methods and reaeents and to &viionmental aspects, such as the disposal of hazardous materials by proper clean-up, and the maintenance of air quality in the laboratory. Many of the preparations involve less than a decigram of primary material. However, we are reminded that emphasis on microtechniques does not imply that the teaching of macrotechniques can he abandoned (I). As one of three undergraduates, Iwell remember our senior assignment, carried out well before World War I1 (1939- 1946). We had to synthesize indigo from naphthalene and to prepare various derivatives of the intermediates. The scale of operations moved from macro through semimicro to real micro as we progressed. We handed in a sizable collection of products-notably, only a few milligrams of indigo!

Techniques such as filtration, distillation, and evapora- tion are eeneral ones and are certainly not restricted to organic chemistry. In their survey of aemimicro experimen- tation in general chemiary,Cheronis and Stein (5) point out that such an approach was recommended for teaching in 1R261 A"--.

An extensive hut by no means exhaustive scrutiny of Jour- nal of Chemical Education from I945 through 1988 elicited some 50 naoers. some with references to earlier times. deal- ing with'va'riouk aspects of small-scale organic operations. Mv im~ression is that the hieh-interest neriods in the teach- . . ing aspects are somewhat hifore and d k n g World War 11, soon after demohilization, and the present.

In 1945 Cheronis and his co-workers published parts VI and VII of their series "The Use of Semimicro Technic in Organic Chemistry" (6, 7), with a literature survey going back of 1919 (6). There is little doubt that Cheronis was IargeIy responsible for the initial growth of interest in the teaching of organic chemistry by small-scale methods. Apart from his papers, his books (8, 9) and his lectures inspired others to try small-scale techniques.

One who was ins~ired was E. Kline. Professor Emeritus a t the University of donnecticut. ~1ine;still professionally ac- tive. makes the followine statement in the refa ace to his book (10):

- In September, 1941, Dr. Nicholas D. Cheronis described his

experiences with semi-micro procedures at the Atlantic City meeting of the American Chemical Society. He exhibited some of the apparatus used and asked for instructors to volunteer in testine some of the oroeedures whieh he had devised and whieh were &scribed in 8 mimeographed manual which he had pre- pared. The author was one of those who volunteered.

Kline (who is an expert glassworker) goes on to say that apparatus was constructed and assigned to eight students. By the summer of 1942, all first-year students were equipped with small-scale glassware. A reminder of the pioneer efforts of Cheronis and Kline appeared quite recently (11). Kline tells me of the dramatic rise in student intake after the end of the War. Supplies and bench space were limited; it was then that his small-scale annaratus and technioues received . . and passed their most stringent test. Ingeneral, the prepara- tions described hv Cheronis and bv Kline involve several grams of primary material. Subsequently, Cheronis gave in-

898 Journal of Chemical Education

structions, with a few examples, for microscale synthesis (12).

Soon after demohilization, I was teaching in a small Lon- don college. We had shortages similar to those mentioned by Kline. We had only one chemistry teaching laboratory; this was occunied bv successive erouos of students both dav (including ~atu;day m~rnin~jandevening. M. A. Fill (then senior lecturer in organic chemistry, now still active) and I had gained considerable expertise in microchemical opera- tions during the War; also, we knew of the earlier work of Cheronis. I t seemed that our handicaps might be alleviated by providing sets of small-scale apparatus in compartment- ed boxes. By strict enforcement of "clean-up" rules, the boxes could be handed in a t the end of a session and, when necessary, reissued 10 min later to the next student group. Breakages were minimized by the use of springclamps, rath- er than screw ones. Preparations were mainly in the sub- gram range; a few were truly micro.

The success of this an~roach was almost entirely due to the ingenuity and dediEaiion of Fill. We needed apparatus that was com~arativelv inexnensive (at that time, our bud- get would not run to & ~ u n d - ~ l a s s joints!), quick to put to- gether, and easy to keep in good shape. By standardizing stem and neck diameters, we were able to use identical pre- bored corks in most of the assemblies.

When the post-War rush subsided, Fill instituted a short course on small-scale techniques, held on Saturday morn- ings. This course, intended mainly for teachers, had several consequences. The demand for equipment was met by Grif- fin and Georee. Ltd.: in 1951. tbis firm introdhced the "Mi- - . croid Semi-micro Organic Set," based on our designs. The fieure shows a diaeram made bv Fill to illustrate some of the p&ible assembli&. Soon aftecanother supplier marketed a sliehtlv different set.

Teaching loads were horrendous, but we began work on the manuscript of a small, rec college oreanic text (13). This - - effort, naive by modern standards, attempted to show that the practical curriculum is best served by a combination of macro and semimicro techniques.

As soon as funds permitted, a glass-jointed version of the apparatus was developed. To illustrate its versatility, Fill made a douhle-sided unit that carried various assemblies. After its exhibition in 1952. a commercial version of this unit appeared. Interest in this spread to the lay press and, even- tuallv. to the BBC as a feature in its television series "Sci- ence~eview" (14,15). This feature, fortunately filmed, sub- sequently appeared on American TV.

The development of tbis program of small-scale organic chemical equipment and techniques is described in a succes- sion of papers in Journal of Chemical Education (16-23) and elsewhere (24-29). I couple my admiration for present- day efforts to popularize small-scde techniques with a com- ment: often, we make progress by standing on the shoulders of our predecessors.

Literature Clted 1 . Stinan, S. C h m Eng. N e m 1989,67, (9l.32. 2. Wi1iiam.on. K. L. Mmeroleola ond Microacolr orgonir Erpsrimtnts; Heath: Lexing-

tan. MA. 1989. 3. Mayo. 0. W.; Pike. R. M: Butcher. S. S. Mirrozcoie O~aanic Lcborofory, 2nd ed.;

Wiley: New Ymk, 1989.

A b r n a t i v e assembl ies from standardized components.

4. Butcher, S. 8.: Msyo, D. W.: Pike, R. M.; Fook, C. M.: Hotham, J. R.; Page, D. S.J. 15. Stock,J.T.J. Cham.Educ. 1357.34.358. C h ~ m . Edue 1995,62,147. 16. Stock, J.T.:Fill, M. A. J. Chem.Educ. 1953.30.296.

5. Cheranis, N. D.:Stein,H. J Chem.Edur. 1956,33,289. 17. Stock, J.T.: Fi11.M. A. J.Chem.Educ. 1954.31.144. 6. Cheronis. N. D.;Levin. N. J Cham. Edue. 1345.22.85. 13. Sfock,J.T.; Fil1,M.A. J, Chrm.Edue. 1954.31.666. 7. Cheranis, N. D.:Stenn,L.:Csstriuin,V.J. Cham.Educ. 1945.22.107. 19. Stock, J.T.:Fill,M. A. J.Chem.Educ. 1955.32.586. 8. Cheranis, N. D.: Semimicmond M o m Orgonie Chemistry; Crowell: New York, 1942. 20. Stock, J. T.: Fill, M. A. II Cham. Edur. 1956.33.345. 9. Chemnin, N. D.; Entrikin. J. B. Semimicro Qualiloliue Anohis : Crowd: New York, 21. Stock. J.T.: Fi1l.M. A. J.Chem.Educ. 1956.33.619.

1947. 22. Stock, J. T.; Fill, M. A. J. Cham. Edue. 1959.36, 194. 10. Kline, E. R. Sami-miemMelhods in Orgonie Chemlatry; Burgess: Minneapolis. 1947. 23. Stock, J.T.: Fill, M.A.;Bjork, R. G. J. Cham.Educ. 1961,33,524. 11. Campbel1.B. N.Chem.Eng.N<ws 1984,62(19),2. 24. Stmk, J. T.: Fill, M. A. Analyst 1951.76.497. 12. Cheronis, N. D. Semimicro Expan'mmfal Organic Chemistry; de G d k Near York, 25. Stock, J. T.; Fill, M. A. SchodSci. Rau. 1952.33. 331.

1958: p 287. 26. Stock, J.T.: Fi1l.M. A. SchoolSci. Re". 1956.37.346. 13. Stock. J. T.; Fill. M. A. Introduction to O~ganic Chemistry; Uniwrsity Tutorial: 27. Stock, J.T.; Fill, M.A. SchaolSci. Re". 1961.43, 130.

London, 1955. 28. Stock, J.T.; Fill, M.A. Lob.Pmcficr (London) 1956.5.344. 14. Stock, J. T.: Fill, M. A. Chrm. Producla (London) 1955, 18,428, 29. Stock, J.T.;Fill, M.A.Lob.Prarlira (London) 1957.6. 38.

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