B.
Adamantane. In a
500-ml. Erlenmeyer flask having a 24/40 standard taper joint are placed
200 g. (1.47 moles) of molten endo-tetrahydrodicyclopentadiene and a
magnetic stirring bar. A
well-greased inner joint (2.2 × 15 cm., 24/40) is fitted into the top of the flask to serve as an air condenser, and
40 g. of anhydrous aluminum chloride is added through the opening (Note
3). The reaction mixture is simultaneously stirred and heated at 150–180° (Note
4), (Note
5) by means of a combination
magnetic stirrer-hot plate.
Aluminum chloride sublimes to the top of the flask, especially at the beginning of the reaction, and the accumulated sublimate is, from time to time, pushed down into the reaction liquid. After the mixture has been heated for 8–12 hours, the flask is removed from the hot plate-stirrer and the black contents upon cooling separate into two layers. The upper layer, a brown mush of
adamantane and other products, is decanted carefully from the lower black tarry layer into a
600-ml. beaker. The Erlenmeyer flask is rinsed five times with a total of
250 ml. of petroleum ether (b.p.
30–60°) with decantation into the same beaker (Note
6), (Note
7). The
petroleum ether suspension is warmed until all the
adamantane is in solution; there should be an appreciable excess of solvent. The solution is decolorized by careful addition of
10 g. of chromatography-grade alumina, the hot solution filtered, and the
alumina and the beaker washed thoroughly with solvent. The nearly colorless filtrate (Note
8) is concentrated to a volume of about 200 ml. by distillation and then cooled in a
Dry Ice-acetone bath. The solid
adamantane is removed by suction filtration and there results
27–30 g. (
13.5–15.0%) of crystals, melting point about
255–260° (Note
9), (Note
10). One recrystallization from
petroleum ether raises the melting point to
268–270° (Note
11), (Note
12).