the microscale laboratory Fractions of 0.5mL are collected in small test tubes or vials. If desired, the flow rate can be increased by applying pressure using a small pipet bulb with caution that the column packing is not sucked back into the bulb. The magenta colored Cso solution is colleded in two to three fractions. Only Csoelutes from the column. The higher fullerenes remain on the column under these conditions. A simple way to obtain an infrared spectrum is to evaporate the material onto a KBr disk to form a film;4however, evaporating directly from the eluate gives background toluene absorptions.Abetter procedure is to transfer a few drops of the eluate to a small vial and evaporate to dryness using a stream of N2. The material is redissolved in carbon disulfide (HOOD), and this solution is applied to the salt plate dropwise until a mustard colored film of the desired thickness is deposited. Agentle stream of N2 is blown over the plate to remove as much of the residual solvent as possible. The four sharp fullerene absorptions at 1429,1181, 576,and 527 cm-' (6) are observed easily. There may be an absorption a t 1500 an-' from residual CS2, but this does not interfere with the fullerene spectrum. When no longer needed, the film can be washed off the plate with a few drops of toluene. To obtain a UVIvisible spectrum, a drop of the toluene solution is placed in a small tube and the solvent blown off with Nz. Enough hexane to fill a cuvette is added and the mixture allowed to stand a few minutes with occasional shaking. Enough of the fullerene dissolves in the hexane to allow a spectrum to be obtained directly. There are strong absorptions at 213,257,and 329 nm with a weak band at 404 n m (7). If an FT NMR spectrometer with a carbon channel is available, a spectrum can be run taking advantage of the recent observation that fullerenes are quite soluble in 1,2dichlorobenzene (8, 9).For an NMR the separation needs to be run on a larger scale or with several student samples pooled to obtain 5-10 mg of material. This is dissolved in 0.4 mL of dichlorobenzene and about 10 vol % of deuterobenzene added for an internal lock. A13C spectrum can be obtained in about two hours. Cso fullerene has a single peak at about 143 ppm. The much larger dichlorobenzene %se of KBrdisks is mandatory. NaCl disksabsorb strongly and cut off the two lowest wavenumber fullereneabsorptions.
peaks are further upfield a t 132.6, 130.5,and 127.7 ppm and do not overlap with the fullerene peak. Acknowledgment
This experiment was developed as part of a project to establish an Undergraduate Instrumentation Center, supported by the National Science Foundation Instrument and Laboratory Improvement Program under grant DUE 9150974. Literature Cited
1. Kr0to.H. W.:Heath,J.R.;OBlien.S.C.:Curl,R.F;Smdey,R.E.NoNm 1965,318, 162-1M. 2. F a an histoticel review by oneof the diezoverersofhuerenes see: Kmta.H. W AM. Cham k t . Ed. Engl. 1882,91,111-129. 3. Smlvena, W. A,; Bedworth P V; 'Ibw J. M. J. Am. Cham. Sor 1992,114,7917-7919. 4. lawe, D.W.; Potter,W T.;Teeters, D. J Chem. Edue. 1882.69, 663. 5. Craig, N. C.; Gee, G. C.; Jahn8an.A. R. J. Chem. Edvc 1SSZ. 69,66P668.
6. Cor,O.M.;Behal,S.;Diako,M.;Crmn,S.M.;Crpaney,M;Hsu,C.S.;Kollin,E.B.; Mil1ar.J.;Robbina. J.; Robbins, W.;Shed.R.D.;?indall.P. J.Am. Chom. Soc. 1891,113.2940-2944. I. H a , J. P; Kmto, H. W: Taylor, R Chrm. Phys. h t t . 189l.177,S9P397. 8. 8etivens. W.A.:Ibur, J. M. J. Cham. Soc.,Cham. Commun. 1895,1207-1209. 9. Ru&, R. S.; B e , D. S.; Malhoha, R.; Lments, D.C. J. Ph? Cham 1992.97.3315L 3383.
Microwave Synthesis of Tetraphenylcyclopentadienone and Dimethyl Tetraphenylphthalate John W. Elder
Fairfield University Fairfield. CT 06430 A recent paper (1)has reviewed the advantages and some of the applications of the use of microwave heating in the organic laboratory. We have found that microwave heating is useful in the synthesis of tetraphenylcyclopentadieneoneand dimethyltetraphenylphthalate, a sequence that appears in whole or in part in many organic laboratory books (2). The microwave method in both the condensation and Diels-Alder reactions is not only faster but also much simpler to perform and gives products of high purity without a complicated work-up. The microwave oven used was a Sharp Carousel I1model R-4A73.Five to 10 reactions were run simultaneously. (Continued on page A144)
A142
Journal of Chemical Education
the microscale laboratory
Tetraphenylpentadienone
In a 13- x 100-mm tegt tube are placed 105mg(O.5 mmol) of bend and 105mg (0.5 mmol) of 1,3-diphenylacetone. One milliliter of w 4 triethylene glycol is used to wash down the sides of the \ test tube.The contents are No, mixed and the test tube is irradiated in the micr* wave for 1 min at 50% power. Ten drops of Mton B are added and mixed with the contents. The test tube is returned to the micmwave and irradiated another minute at 50% power. When the tegt tube has cooled enough to handle, 1 mL of methanol is added and miKed with the contents. ARer further cooling, the dark precipitate is collected in a Hirseh funnel and washed with cnld methanol. The precipitate is dried by drawing air through it and pressing it between filter paper. The average yield is 75%, mp 21&218 OC. Dimethyl tetraphenylphfhalate
In a 50-mL heaker are p l a d 39 mg of tetraphenylcyel* pentadienone (0.1mmol), 3 drops (an excess)of dimethyl acetylenedicahxylate and 11 of triethylene g l p l . These are mixed by swirling,covered with a watch glass and irradiated in the micmwave oven at 50% power for 5 min. During this time the dark color of the tetraphenyleyclopentadienon~ disappears and the solution assumes a golden color. As it m l s slowly to room temperature colorleas crystals of the pmduct separate slowly These are wlleded in a Hirsch funnel and the remaining crystals are washed from the beaker with a little cold 95% ethanol that also is used to wash the oystals in the filter. Recrystallizationin 95%ethanol gave an average yield of 85%, mp 255-257'C. I.BadS.S.;Bme.A.J.;Chau-,A.G.;Msnhaa,M.S.;Rqju,V.S.;Robb,E.W.J. Chrm Edur 1882.69.92&929. 2.la)Fieaor.L. F.;Willisman, K L. OlgonielLartina. 4th cd.; Hcath.Lexir.gtm, 1979: p p n 2 2 1 6 . @ ) Mayo, D. W.; Kke,R. M.; BuWls, S.S.Miemsmlr h g M i e i n b o rotm 2nd 4.; Wiley.Ncw%rh 1989: pp 381*. (cl Pans, D. I*; h p m a n , G. M.;Kri..G. s.;Engel. R G. h ~ ~ i t ooO wnn i e L o l a m t o y Ikhniqw% saun. ders, Philadelphia, 1990; pp 287.290 (dl Wilmr. C . F. E~p.rimontnlO g o e Chonus@y; Maemillan: New York. 1988: pp 3 4 1 4 4 4 . (e) Williamson. K . L. 1989:pp47& M ~ m s m l r ~ d hMg M~i ekE ~ p . r i m n l s ; H c a t hLexinm, : 479.
Direct bromination of aniline produces a variety of polybrominated and oxidized products and direct nitration also leads to oxidized pmducts. Besides this, in acid solution the anilinium ion is formed, and this charged group acts as a deactivator and a meta diredor. By adding the acetyl group, one arrives a t a molecule that does not readily oxidue and substitutes largely at the rrara msition. A second substitution takes place-aithe posiiion okho tn the carbon carrying the acetamido group. Hydrolysis of the amide function pves the desired 4-brome2-nitroaniline. This sequence has been performed by nearly one hum dred students. More than 95%of these have completed the sequence in 3-3 112 h with a reasonable yield of the final pmduct. Procedure
In a 25-mL Erlenmeyer flask is placed 465 mg (5 mmol) of aniline, 12 mL of water, and 0.5 mL of concentrated hydrochloric acid. The mixture is swirled to dissolve the aniline. Asolution of 750 mg of sodium acetate trihydrate in 2 mL of water is prepared for the next step. To the flask containing the aniline, 1.0 mL of acetic anhydride is added with mixing followed immediately by the sodium acetate solution. The.flask is placed in an ice bath and stirred as the product crystallizes. When the reaction seems complete, the solid is collected in a Buchner funnel and washed with a little ice water. The product isdried by. pulling air thmugh the filter cake, and pressing it between fdter papers between paper towels. This material is pure enough to be used in the next step without purification. Bromination
4-Bromo-2-Nitroaniline: A Multistep Synthesis John W. ~lder'and Mark A. Paollllo
Failfield University Failf~eld,CT06430
Multistep organic syntheses often are required when direct methods give undesirable hyprodncts. These multisteo nrocesses are challeneine but freouentlv involve pm&dbes and products unfahTar to students ( j ) .We describe here the svnthesis of a relativelv simnle comwund that can he madeonly indirectly,hut us& methods &at are both easy to perform and familiar to students. '~uthorto w h m correspondence should be addressed. A144
Journal of Chemical Education
I n a 25-mL Erlenmeyer flask, the slightly moist acetanilide is dissolved in 4 mL of glacial acetic acid. ARer the addition of 1.6 g of pyridinium bromide perbromide, the contents are mixed and heated in a 60°C water bath for 10 min. FiReen milliliters of water are added along with 2 mL of saturated sodium bisulfite solution. (If the orange color persists, another milliliter of saturated sodium hisulfite solution is added.) ARer being mixed, this is cooled in an ice bath for 5 min. The crystals are collected in a Hirsch funnel, washed with water, and partially dried by pullingair through them and pressing them between filter paper. Final drying is accomplished by heating the crystals on a watch glass over a beaker of boiling water. The crystals must be dry for the followingreaction t o work.
