can be eluted by pure hexane, and the ketone product, 2'acetonaphthone, is eluted with the slightly more polar solvent as detailed in the experimental section. Concluslon We feel that the Wacker oxidation experiment as described is cost-efficient due t o the small scale employed. This experiment should prove to be a valuable addkion to the undergraduate organic curriculum. It could be effectively used as an example of an oxidation process, a complex but readily understood catalytic process, as well as an effective preparative microscale chromatographic separation.
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Acknowledoment We would like to thank Smith, Kline and Beehham Pharmaceuticals and the GTE FOCUS . promam for their financial support of this project.
Literature Clted I. 2 3. 4.
Tsuji, J.; N~gashima,H.; Nemoto, H. Organic Synthesis 1984,62,%12. Williamron, K. L. Microscole Or~onicLdomlov; Heath: Lexington, MA, 1987. Catalog afthe Aldrich Chemical Company: Milwaukee, WI, 1988, p 9. Tmt. B. M.; Verhaven. T. R. In Comprehensiu~Orgonamernllie Chamiatry; Wilkin~ son. G., Ed.:Pergamman: Oxford. 1977; Vol. 8, p 884.
5.
Smidt.J.;Hafner,W.;Jira,R.:Sedlmeicr,J.;Sieber,R.;Ruttbger.R.:Kojer,H.Angew.
Esterlfkatlon of Adlplc A d d to Dlefhyl Adipate The dry adipic acid obtained from the oxidation of cyclohexanolis transferred to a 10 mL microware flask containine a micro soin bar. Three milliliterr ahsolute ethanol, 1.5 mL toluene, and 0.1 ml. concentrated sulfuric acid are added, a Hirkman distillation head is attached, and the apparatus rs placed in a sand bath at 120'C. The temperature is increased as needed, until at Least 3 mL of the azeotropie distillate of water, ethanol, and toluene has been collected, asmeasured by transfer witha Pasteur pipet to a small graduated cylinder. This process is repeated by adding 3 mL absolute ethanoland 1.5 mL toluene to the flask and again distilline.until no u. more liquid comes over. The apparatus is now arranged for vacuum distillatron, and diethyl adipate is collected. 'The boiling point is in the neighborhood of 150 'C at 60 tom. a realistically ohtainable pressure with aspirators and the microware joints. Gas ehromatographic analysis should confirm a relatively pure sample of diethyl adipate. ~~
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Acknowledgment Funding from the Pew MemorialTrust, the DuPont Company, and the Haverford College Faculty Research Fund is gratefully acknowledged.
A Small Scale Equilibrium Experiment
Chem. 1959.71.176182.
Patrlck Flash
KeM State Unlvemtv-AaMabula 3325 W 13th AsMabula. OH 44004
From Cyclohexanol to Diethyl Hexanedioate [Diethyl Adipatel: A Two-step Synthetic sequence tor ~icroscaleorganic iaboratory Claude E. Whiner and Chrlstlna A. Gray HaveI1ord Colleee Hawelford, PA 19041
As an outgrowth of work in our integrated laboratory course for junior majors, we have developed a two-step microscale sequence from eyclohexanol through adipic acid to diethyl adipate that has proved to be successful in the firstyear organic laboratory. Experimental details are as follows. Oxldatlon of Cyclohexanol to Adlplc Acld Two milliliters concentrated nitric acid (70% nitric acid, density 1.42: 0.032 mol) is transferred to a 10-mL microware flask containing a micro spin bar. A condenser is attached, and the apparatus is placed in a sand hath set at 55-60 'C in the hood (because oxides of nitrogen will he liberated). When temperature equilibrium has been reached, 1 mL (0.95 g: 0.0095 mol) cyclahexanol is added with a Pasteur pipet through the condenser aver a period of 20-30 min, that is, at a rate of about 1droplmin. Care must he taken that tbe cyelohexanol is kept warm enough so that it does not solidify in the pipet and that it is dropped directly into the reaction mixture so that it does not solidify on the condenser walls. Caution: The reaction is extremely vigorous; it should he allowed to subside after each drop before addition of the next one. When addition is complete, the flask is held at 55-60 O C for a further 30 min, then heated to 95 OC over a period of 15 min, held at 95 'C for 5 min, cooled to room temperature, and finally cooled inan ice hath. The resulting crystals of adipic acid are filtered with suction, using a small Hirsch funnel, washed with a very small amount of ice water, and allowed to dry on a watch glass. Between 0.5 g and 1.0 g dry crystals of adipic acid should he obtained. meltine at about 150 "C (literature: 151-153 TI. 'The crystals contain small amounts of autcinic and glutarir acid but are ofsuifreientpurity to becarried forward without recrystalliratron to the next step. (Recry~talli~ation from water rerults in relatively severe losses.) ~~~~~
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Camom
Manv general chemistrv lab manuals include an experiment in which the equilib;ium constant for the iron-thiocyanate complex is determined. The procedure where the concentrationof the complex ion is determined spectrophotometrically for separate solutions' has often given us physically impossible results for low concentrations, while the procedure where small amounts of iron solutions are added to a large volume of thiocyanate solution2 requires excessive solution transfer. s data points. has never The latter Drocedure ~ r o v i d emore given physic~llgimpossible data, and requi&student use of eraohine . skills to obtain the value for K. In order to reduce the volumes of solutions used and to lessen the problem of spillage, an alternate method for running this lab has been developed. In this method 6.0 mL of thiocyanate solution is placed in a Spectronic 20 cuvette with a small triangular spin vane at the bottom. Ten 0.06-mL aliquots of iron solution areadded to the ruvette via a 1.00-mL oioet. After each addition. the cuvette is held over a magdetk stirrer for about 15 s to ensure thorough mixing and placed in the Spectrouic 20 for an absorbance reading. This new ~ r o c e d u r ehas cut the volumes of solutions used by over 90%;lessened the spillage-transfer problem, and cut the time reauired to collect the data for the determination of K so greatiy that a qualitative study of the equilibrium reaction was added to the lab. A copy of the experimental procedure and a BASIC program for analyzing the student data are available from the author by sending a SASE.
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Slowinski, E. J., et al. Chemical Principles in the Laboratwy. 5th ed.: W. 6. Saunders: New York. 1989: Exoeriment 21. Hudak. N. J. ~odular~aboritoty~rog;amin Chemisny.Chemical Ed~cat~on Resources. Inc.: Palmyra. PA. 1988: EQUL 343.
Volume 67
Number 4
April 1990
341
