Adamantane

Adamantane is a colorless, crystalline chemical compound with a camphor-like odor. With a formula C10H16, it is a cycloalkane and also the simplest diamondoid. Adamantane molecules consists of three connected cyclohexane rings arranged in the 'armchair' configuration. It is unique in that it is both rigid and virtually stress-free. Adamantane is the most stable among all the isomers with formula C10H16, which include the somewhat similar twistane. The spatial arrangement of carbon atoms in the adamantane molecule is the same as in the diamond crystal. This motivates the name adamantane, which is derived from the Greek adamantinos (relating to steel or diamond).AdapaleneAdapromineAmantadineBromantaneMemantineRimantadineSaxagliptinTromantadineVildagliptinAdamantaneHexamethylenetetraminePhosphorus pentoxidePhosphorus pentasulfideTetramethylenedisulfotetramineTetrodotoxinArsenicin A Adamantane is a colorless, crystalline chemical compound with a camphor-like odor. With a formula C10H16, it is a cycloalkane and also the simplest diamondoid. Adamantane molecules consists of three connected cyclohexane rings arranged in the 'armchair' configuration. It is unique in that it is both rigid and virtually stress-free. Adamantane is the most stable among all the isomers with formula C10H16, which include the somewhat similar twistane. The spatial arrangement of carbon atoms in the adamantane molecule is the same as in the diamond crystal. This motivates the name adamantane, which is derived from the Greek adamantinos (relating to steel or diamond). The discovery of adamantane in petroleum in 1933 launched a new field of chemistry dedicated to studying the synthesis and properties of polyhedral organic compounds. Adamantane derivatives have found practical application as drugs, polymeric materials, and thermally stable lubricants. In 1924, H. Decker suggested the existence of adamantane, which he called decaterpene. The first attempted laboratory synthesis was made in 1924 by German chemist Hans Meerwein using the reaction of formaldehyde with diethyl malonate in the presence of piperidine. Instead of adamantane, Meerwein obtained 1,3,5,7-tetracarbomethoxybicyclononane-2,6-dione: this compound, later named Meerwein's ester, was used in the synthesis of adamantane and its derivatives. D. Bottger tried to obtain adamantane using Meerwein's ester as precursor. The product, tricyclo-, was not adamantane, but a derivative. Other researchers attempted to synthesize adamantane using phloroglucinol and derivatives of cyclohexanone, but also failed. Adamantane was first synthesized by Vladimir Prelog in 1941 from Meerwein's ester. With a yield of 0.16%, the five-stage process was impractical (simplified in the image below). The method is used to synthesize certain derivatives of adamantane. Prelog's method was refined in 1956. The decarboxylation yield was increased by the addition of the Heinsdecker pathway (11%) and the Hoffman reaction (24%) that raised the total yield to 6.5%. The process was still too complex, and a more convenient method was found in 1957 by Paul von Ragué Schleyer: dicyclopentadiene was first hydrogenated in the presence of a catalyst (e.g. platinum dioxide) and then transformed into adamantane using a Lewis acid (e.g. aluminium chloride) as another catalyst. This method increased the yield to 30–40% and provided an affordable source of adamantane; it therefore stimulated characterization of adamantane and is still used in laboratory practice. The adamantane synthesis yield was later increased to 60% and 98% by ultrasound and super acid catalysts. Today, adamantane is an affordable chemical compound with a cost of about $1 a gram. All the above methods yield adamantane as a polycrystalline powder. Using this powder, single crystals can be grown from the melt, solution, or vapor phase (e.g. with the Bridgman–Stockbarger technique). Melt growth results in the worst crystalline quality with a mosaic spread in the X-ray reflection of about 1°. The best crystals are obtained from the liquid phase, but the growth is impracticably slow – several months for a 5–10 mm crystal. Growth from the vapor phase is a reasonable compromise in terms of speed and quality. Adamantane is sublimed in a quartz tube placed in a furnace, which is equipped with several heaters maintaining a certain temperature gradient (about 10 °C/cm for adamantane) along the tube. Crystallization starts at one end of the tube, which is kept near the freezing point of adamantane. Slow cooling of the tube, while maintaining the temperature gradient, gradually shifts the melting zone (rate ~2 mm/hour) producing a single-crystal boule. Before adamantane was synthesized, it was isolated from petroleum by the Czech chemists S. Landa, V. Machacek and M. Mzourek in 1932.They used fractional distillation, which separates the organic molecule components of petroleum based on their boiling points. Landa et al. could produce only a few milligrams of adamantane, but noticed its high boiling and melting points. Because of the (assumed) similarity of its structure to that of diamond, the new compound was named adamantane.