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|Section2= |Section3= }} ()Propellane is an organic compound, the simplest member of the propellane family. It is a hydrocarbon with formula C5H6 or C2(=CH2)3. The molecular structure consists of three rings of three carbon atoms each, sharing one C-C bond. ()Propellane is a highly strained molecule. The bonds of the two central carbon atoms have an inverted tetrahedral geometry, and the length of the central bond is 160 pm. The strength of that bond is disputed; estimates vary from 59–65 kcal/mol to no strength at all. The energy of the biradical state (without the central bond and unfilled central carbons) is calculated to be 80 kcal/mol higher. The compound is highly unstable, and at 114 °C it will spontaneously isomerize to 3-methylidenecyclobutene with a half-life of 5 minutes. Its strain energy is estimated to be 102 kcal/mol (427 kJ/mol). The type of bonding in this molecule has been explained in terms of charge-shift bonding 〔 Wei Wu, Junjing Gu , Jinshuai Song , Sason Shaik , Philippe C. Hiberty (2009), ''The Inverted Bond in ()Propellane is a Charge-Shift Bond''. Angew. Chem. Int. Ed. volume 48, 1407–1410, 〕 ==Synthesis== ()Propellane was first synthesized by K. Wiberg and F. Walker in 1982,.〔 K. B. Wiberg, F H. Walker (1982), ''()Propellane''. J. Am. Chem. Soc. volume 104 issue 19, pp. 5239–5240; 〕 according to the following schema: : Synthesis begins with conversion of the 1,3-di-carboxylic acid of bicyclo()pentane 1 in a Hunsdiecker reaction to the corresponding dibromide 2 followed by a coupling reaction with ''n''-butyllithium. The final product 3 was isolated by column chromatography at -30 °C. However, a much simplified synthesis was published by Szeimies.〔J. Belzner, U. Bunz, A. D. Schlüter, G. Szeimies et al. "Concerning the synthesis of ()Propellane" Chem. Ber. volume 122, pp.397-398〕 It starts with dibromocarbene addition to the alkene bond of 3-chloro-2-(chloromethyl)propene 6 followed by deprotonation by methyllithium and nucleophilic displacements in 7〔 (1998) Organic Syntheses, Coll. Vol. 10, p. 658 (2004); Vol. 75, p.98 (Online article ). 〕 not isolated but kept in solution at −196 °C. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「1.1.1-Propellane」の詳細全文を読む スポンサード リンク
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