J. C. Kellett, Jr.
School of Pharmacy Universitv of North Carolina Chapel Hill, North Carolina
II
A Eeb-Alder Student f'reporotion
W e find that a Diels-Alder reaction between tetracyanoethylene (Columbia Organic Chemicals Co., Inc.) and anthracene (Eastman pActica1) serves very well for a simple, rapid student preparation for our course in organic chemistry for pharmacy students. The formation of this adduct was first reported by Middleton, et al.,' using tetrahydrofuran as a solvent; later, Schimelpfenig2employed the reaction in benzene as a lecture demonstration. We use a mixture of these solvents to reduce the volume of the reaction mixture and yet provide a system in which the addnct is insoluble. We discuss in the prelaboratory session a simple mechanism of the Diels-Alder reaction which includes the formation of a pi-electron complex. It is pointed out that the green color observed in this reaction could be such an intermediate, but that the issue has not been proven. The discussion also covers formation of other pi-electron complexes by tetracyanoethylene with aromatic systems. A variety of these are mentioned (with color photographs) in a Chemical & Engineering News special feature a r t i ~ l e . ~ Using the parent structure 990-ethanoanthracene,' we named the product 9,lOdihydro-ll,11,12,12-tetra'MIDDLETON, W. J., HECKERT,R. E., LITTLE,E. L., AND KBESPAN,C. G., J. Am. Chem. Soc., 40. 2783 (1958). 'SCHIMELPI%NICI, C. W., J. CHEM.EDUC.,36, A379 (1959). %cKns~cx. B. C.. AND BIEHN.G. F., Chem. and Eng. News,
cyano-9,lO-ethanoanthracene. A name based on bicyclooctane was also devised, and a tinkertoy model prepared to illustrate the unusual structure and to point up the basis for naming.
-["-"I+-
complex
+ NC,
,CN
C
II
C
NC'
'CN
The Experiment
A solution of 1.3 g anthracene is prepared in 100 ml benzene contained in a 250-ml beaker. A freshly prepared solution of 0.7 g tetracyanoethylene in 5 ml of tetrahydrofuran is then added. Immediately a dark green color forms which soon begins to fade. As the color fades, a flocculent precipitate of adduct forms; in less than 10 min, with only occasional agitation, the green color has disappeared and precipitation is complete. The precipitate is filtered with suction and then recrystallized from a minimum amount of acetone. The yield of once-recrystallized material is about 80%. It melts a t 263'(d) (sealed tube); reoorted 268-270°.' 'PATPERSON,A. M., CAPELL,L. T.,AND WALKER,D. F., "The Ring Index," 2nd ed., ACS, Washington, D. C., 1960, p. 720.
Volume 40, Number 10, October 1963
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