Carl H. Snyder Henry Hubinger, and Susan Jane Cole University o f Miomi Coral Gables, Florida 33124
A Synthetic-Analytical Organic Laboratory for the Nonmaior
A high level of current interest in nontraditional organic laboratory courses is evident from the regularity with which articles discussing such courses appear in the literature (1-4). Many of these articles describe .novel approaches to the organic laboratory which unquestionably provide the student with a challenging and academically rewarding course, one which the student genuinely enjoys and leaves with the satisfaction of having learned something about science, organic chemistry and laboratory procedure. Yet a close examination of many of the articles reveals that the approaches used may be prohibitively expensive to some schools in terms of total hours of laboratory operation (I), the total amount of time required of faculty and assistants ( Z ) , or very low studentlteacher ratios (3). For several years we have used for our nonmajors sequence a novel approach which does not exhibit these weaknesses. In a sense, the approach we descrihe here offers the best of two worlds: the highly structured, organized course appropriate to relatively high studentlteacher ratios and rigorously limited laboratory sessions; and the unstructured, superficially unorganized laboratory in which progress depends on the student's own motivation and reasoning ability. This combination of formality and freedom is achieved by starting the course in the traditional sense, with a pair of elaborately described syntheses and deliberate guidance in the appropriate laboratory procedures, and then, in the second part of the course, by providing each student with several carefully chosen unknowns to be identified a t his or her own pace and with techniques learned in the earlier, synthetic phase. Our objectives in developing this course were: 1) to provide the nonscience, terminal student with an exciting, yet academically sound exposure to the organic laboratory; 2) to capture the interest of the large fraction of our students majoring in consumer and medically related fields, including home economics, nursing and medical technology; 3) to accommodate students with widely differing degrees of previously acquired laboratory skills (the prerequisite to the course is one semester of introductory chemistry and during the summer the course normally attracts a substantial number of transfer students from a variety of schools); 4) to permit efficient operation of the course with a studentfteacher ratio of about 3011 and in a laboratory session limited to 3 h / w k for 15 wk; and 5) to introduce students to laboratory techniques ranging from simple distillation ta spectrometric analysis and to the use of library reference aids for solving laboratory probI--.
,ems.
witb the of Specifically, the Course acetylsalicylic acid by the acetic anhydride acetylation of salicylic acid,' followed by the determination of the product'; melting- noint. . . solubilities in acidic and ha& solvents, neutralization equivalent, pH, and infrared spec. trum. The synthesis is a simple, one-period experiment which produces a product (aspirin) familiar to all students and which immediately establishes the of chemistry in today's society" (3). The product, moreover, lends itself to quantitative examination through the determination of the acid's neutralization equivalent. After completing the examination of acetylsalicylic acid 56 / Journal of Chemical Education
as a typical organic acid, the students prepare 2-octanone by the dichromate oxidation of 2-octanol.2 Here they learn techniques of steam distillation and simple distiilation, and learn to use a refractometer. In anticipation of the second oart of the course. soluhilitv and DH differences between 2-octanone and &etylsali&lic acid are emphasized. The preparation of 2-octanone is easily carried out in two laboratory periods; the product, a liquid ketone, affords an introduction to the preparation of crystalline derivatives of liquid compou~ds.-An examination of the properties of the 2,4-dinitrophenylhydrazone of 2-octanone, prepared by the method of Shiner, Fuson, and Curtin ( 5 ) , gives the student additional experience in working with crystalline solids. With the conclusion of the synthetic phase of the course, which occupies approximately the f i t five weeks of the semester, the student is given a pair of unknowns, one liquid and one solid. He or she is told only that one unknown is an acid and the other is a ketone. Here the laboratory becomes informal (but still opens and closes a t its reeularlv scheduled times) and the students are encouraged t d u s e their own initiative in applying the observations of the properties of acetylsalicylic acid and 2-octanone in differentiating between the two unknowns. Successful identification of the acid and the ketone as such is followed by determination of the physical constants of the unknowns. The acid is further characterized by its neutralization equivalent and the ketone by the mp of its 2,4-dinitrophenylhydrazone. With this data and readily available tabulations of appropriate physical constants (6, 7), the student is usually able to identify the two unknowns or to narrow his or her choices to a verv few compounds. Confirmation or final identification is arcomplished by a comparison of the infrared sperrra of the unknowns with a c&m~ilationof the identified soectra of all the unknowns used-in the course, and a number of other acids and ketones as well. We have found that approximately ten 3-hr laboratory periods-the second portion of the course--constitute an adequate period of time for the slower students, working at their own pace, to complete the identification of the two unknowns. The more capable students can receive additional unknowns for extra credit, while the superior students are introduced to qualitative elemental analysis by the calcium oxide-zinc decomposition (8), and to the rudi-
'The p w e of this article is to describe a laboratory course of general interest rather than to present detailed experimental data. Accordingly, we simply note that directions for the prepmation of acetylsalicylic acid can he found in several recent laboratory manuals. Although same of these describe the use of an ether-petroleum ether mixture for recrystallization, we prefer hot ( n ~bailing) t water to circumvent a potential flammability haz. ard. We are indebted to H. P. Schultz of this Department for eaof the diehornate oxidation of 2.actanol, copperimental ies of which are available upon request. Although the dichromate oxidation of isopropyl alcohol to acetone has also been described (9)we prefer the Poctanol oxidation because it appears to be the milder of the two and because Eoctanone is less volatile and therefore more easily handled than acetone.
ments of qualitative and quantitative analysis by gas chromatography. Future plans for the course include the introduction of nuclear magnetic resonance as a spectrometric tool. The course descriotion eiven here is necessarilv eeneral-
unknowns to illustrate the application of these techniques in a problem-solving context, all within a conveniently operated, one-semester, nonmajors laboratory.
meet the needs of individual instructors. The format of location of the compendia for example, and of physical constants and spectra, whether inside or outside the laboratory, are clearly matters of individual taste. What is fundamental to the course, and what has proven so successful with our students, is the use of syntheses and the examination of synthetic products to introduce the fun&mental techniques of the organic laboratory, and the use of
(21 ~ e z k e nD. , C., J C h m Educ., 47.7~0(19701. (31 D'Aurh, J.. GilcMst,A..andJohnstono, J.. J Chm. Edue.. 47,5@8(19701. (4) . . S3nikh.R. B..J Chrm. Educ.. 46,273 (1969) a n d r e f e r e n a s m t a i d therein. (51 sh&. ~aiphL., FW, &pynld. c., and cutin, t avid Y.. he Sy&matic Identification of Organic Compounds." 5th Ed.. John Wiley and Sona, he., New York. 1967, p.253-4. (6) ~ ~ ~ ~ ~ ~ ~ ~ ( ~ ) , ~ ~ . 3 ~ 1 - 1 5 ~ d 3 ~ 2 - 6 5 . (71 w-t, Robert C., (Editor-inChien, "Handbooli of ChemisUy and Physics? 50tb Ed., The Chemical Rubber Co., Cleveland. Ohio, 1969, pp. C-7WX42. ,,( snyder, C.H., S~CMS, J. P..and D ~ I V ~ Ic.J., I ~ >J chpm E ~ Z C . .w , . 72 (19731. (91 w d t e s n . ~ .J. . Cham. Edue., 45.672(18681.
bterature Cited
Volume 5 1 , Number 1, January 1974
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