Indivldualized'Experirnentsfor a Large Introductory Organic Laboratory Class We have adapted several experiments in our large introductory organic chemistry laboratory class to introduce a unique challenge t o eaeh student.' Thus, immediately after learning the technique of recrystallization, students were given a sample of a liquid ketone along with general instructions on how t o prepare a semicarhazone derivative. After recrystallizing the derivative, they identified the starting ketone by determinations of mixture melting points with samples of the authentic semicarbazones. Ten different ketones were found suitable for this exercise: in any one laboratory. only. twostudents had the same starting material. Similarly, an experiment involving the separation of a n acid, a base, and a neutral compound was individualized by giving each student a different mixture and requiring that he separate, purify, and identify the components. A slightly different approach was used with several other experiments. The twenty students in each laboratory were divided into five groups offour working a t the same bench. In one experiment, eaeh group of four was givens different alicyclic alcohol together with general instructions on how to dehydrate the alcohol t o an alkene and how to oxidize the alkene to the rnrresponding dibasic acid. The students were informed which alcohol they had been given, and although all of them p 4 m n e d the experiment individually, each group of four was enmuraged to consult among themselves during the experiment iml tg, discuss the results. In the preparation of an aromatic acid via a Grignard reagent, and in the reduction of a ketone erouo reduced to two or three students. A varietv using sodium borahvdride.. eight .. or nine substrates were used. with the .. 181 i k d dyes and synthetic dye mixtures were sparated inur theircompon~n~c hy column chromntucmphv. Aynin. thr studen& wlvenr polarities, they srranfed among rhemseh.ri tryd,twrenr &an& worked in groups n i l o u r and, y w n inhrrnatim and ~ w n b i n a mr ~s of eluant3 to find the best conditiuns for separation.
.
Students' Choice of Experiments from Which
Most
~
~
Had Been Learned %Students Chooring t h e Experiment as One from Which Most Had Been Learned
Experiment
Control
individualized
s e ~ a r a t l o nof acid, bare, and neutral compound Dehydration and oxidation of an alcohol c o l u m n chromatography Gfigndrd reaction Sodium boronyaride reduction
29 8 14 15
45
4
.
13 18 27 9
Student resDonse to these ex~erimentswas assessed from their reolies to a auestionnaire. This is summarized in the table and indicaies ihat thosestudents performmg theindividualirede~perimentsrons~deredthey had learned moreimm them than a nmtnd gruup all of whum performed the same experimenr. Increased student enrhuiiasm was noted bv i I . teaching assistants. Helpful suggestions have heen received from Professors R. J. Crawford and H. J. Liu to whom thanks :in.r l t ~ t , ' I 'Fife,W. K., J.CHEM. EDUC., 52,119(19751. Fife, W.K., J. CHEM. EDUC.,45,416 (1968).S m i l h li I EDUC.,46,273 (19691. Necken, D. C., J. CHEM. EDUC., 47,700 (19701. ~
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University of Alberta Edmonton, Alberta, Canada T6G 2 6 2
Volume 54. Number 5, May 1977 1 311
