Addison Ault
and Rachel Kopef Cornell College Mount Vernon, IOWO 52314
Preparation of Adamantane A n introductory organic experiment
W e present here a preparation of adamantane which is suitable for use in the introductory organic laboratory. It is based upon the method of Schleyer, the aluminum chloride catalysed isomerization Although the of endo-tetrahydrodicycl~pentadiene.'~~ reaction time is only 1 hr, the yield of crude product, 15%, is about the same as that reported for a reaotion time of 8-12 hr.2 An interesting feature of this procedure is that adamantane is isolated from the hexane extract of the reaction mixture by formation of a beautifully crystalline inclusion complex with thiourea.3 Procedure
Weigh out 4 g of aluminum chloride and store it until ready for use in a stoppered sample vial. Place 10.0 g endo-tetrahydrodicyclopentadiene4 in a 50-ml T19/22 Erlenmeyer flask and fit the flask with a well-greased inner joint which will serve as an air condenser. Clamp the flask so that it can he heated by means of a small hunsen burner flame. Heat the flask gently to melt the tetrahydrodicyclopentadiene. When it has melted, add about of the aluminum chloride down the air condenser and suspend a thermometer in the mixture so that the bulb dips into the liquid as far as possible but does not touch the bottom of the flask. Adjust the flame of the burner so that the mixture is heated just barely to boiling (180-185°C) and is maintained in that condition. Add the remaining aluminum chloride down the condenser in 3-4 portions at about 5-min intervals, and continue the heating for a total of one hour.= During this time, aluminum chloride will sublime into the condenser tube and should be pushed down into the reaction mixture from time to time with a spatula. At theend of the heating period, remove the thermometer and allow the black mixture to cool for an hour. During this time, prepare a solution of 10 g thiourea in 150 ml methanol.' At the end of the cooling period, extract the product from the flask by adding hexane, swirling the mixture, and decanting, being careful not to pour out any of the black, tarry material; use a total of 70-80 ml hexane in 4 or 5 portions. Add 1 g of chromatography grade alumina to the combined hexane extracts and swirl occasionally for about a minute. Filter the extract by gravity into the methanolic solution of thiourea,
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Journol of Chemical Edvmfion
using 10-20 ml of hexane to rinse the flask and filter paper. Stir the two layers together for 2 or 3 min to complete the formation of the beautifully crystalline inclusion complex.' Collect the complex by suction filtration and wash it with about 20 ml hexane. The yield, after drying to constant weight, is 6-7 g. Transfer the crystals (which do not need to be dry) to a 125-ml separatory funnel and add 80 ml water and 40 ml ether. Shake the funnel vigorously for about 5 min, releasing the pressure occasionally, and then allow the layers to separate. If any solid remains, draw off as much of the lower layer as is convenient, add 50 ml more water, and shake vigorously until all the solid has di~appeared.~Dry thc ethereal extract over anhydrous magnesium sulfate and evaporate it to dryness in a tared 50-ml Erlenmeyer flask. The last of the ether can be removed by keeping the flask on its side for about 20 min. The yield is 1.45-1.6 g (14.5-1670) of material with a melting range of 258265°C (sealed ~apillary).~The product may be recrystallized from isopropyl alcohol, using 13 ml/g, with a recovery of about 60%, to give an overall yield of 0.93 g 9 . 3 ) of adamantane with mp 2G8-270°C (sealed capillary) .lo This work was supported in part by funds from the Sloan Foundation.
' SCHLEYZR, P. YON R., J . Am. Chem. Soe., 79,3292 (1957).
a S ~ P. ~YON ~R., DONAI.D~ON, ~ ~ s M.~ M., N I C H O I , ~ ~ , R. D., A N D CUPAS,C., ''Orgmic Syntheses, Vol. 42," (Edilon ROEKELHE~DE, V . ) ,John Wiley & Sons, Inc., New York, 1962,p.8. =LANDA, S., A N D HALA,S., Chem. Lisly, 51, 2328 (19.57); Coll. Czech. Chem. Commun., 24, 93 (1959). Tricyela[5.2.1.0P']decane, Aldrich Cat. No. T5720-7, was used. 6 No stirring or other agitation is necessary. 'The process of dissolubion can be greatly speeded up by stirring with a magnetic stirrer or by heating on the steam bath. ' Saturation of a similar solntion with hexane does not result in crystal formation. If s. larger separatory funnel is available, all the water may be used at once. OStarting with a solution of 1.50 g sdnmantane in 90 ml hexane, 1.07 g of adamantane can be recovered by this process, indicating that adamantme is formed in 21-23% yield in 1 hr. Isotopic dilution anelyse indicate a similar yield. lo Commercial adamantane (Aldrich Cat. No. 10,027-7) can be recrystallized from isopropyl alcohol, using 17 ml/g and cooling only to 0"C, with a recovery of 78%; literature mp: 268270°C.
