1.1.1-Propellane

Highly-strained hydrocarbon ring compound bracket omission [1.1.1]Propellane changed 477208655 [1.1.1]Propellane 1.1.1-propellane.svg 1.1.1-propellane.png 150px Tricyclo[1.1.1.01,3]pentane 35634-10-7 changed ?? correct FDA B99AQN9D35 correct chemspider correct chemspider 1S/C5H6/c1-4-2-5(1,4)3-4/h1-3H2 correct chemspider ZTXSPLGEGCABFL-UHFFFAOYSA-N 125285 142022 C1(C2)(C3)C23C1 5 6 [1.1.1]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. [1.1.1]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 (with no central bond at all) is calculated to be 80 kcal/mol higher. At 114 °C it will spontaneously isomerize to 3-methylidenecyclobutene (5 below) with a half-life of 5 minutes. Its strain energy is estimated to be 102 kcal/mol (427 kJ/mol). Surprisingly, [1.1.1]propellane is persistent at room temperature and is somewhat less susceptible to thermal decomposition than the less strained (90 kcal/mol) [2.2.2]propellane system, which has an estimated half-life of only about 1 h at 25 °C.https://www.thieme.de/shop/Houben-Weyl--SoS/de-Meijere-Butenschoen-Chow-Fitjer-Haufe-Houben-Weyl-Methods-of-Organic-Chemistry-9783131819840/p/000000009583004404 https://web.archive.org/web/20171022033632/https://www.thieme.de/shop/Houben-Weyl--SoS/de-Meijere-Butenschoen-Chow-Fitjer-Haufe-Houben-Weyl-Methods-of-Organic-Chemistry-9783131819840/p/000000009583004404 dead October 22, 2017 Houben-Weyl Methods of Organic Chemistry Vol. E 17e, 4th Edition Supplement (E-Book PDF) - Thieme.de - Thieme Webshop - Armin de Meijere, Holger Butenschön, Hak-Fun Chow, Lutz Fitjer, Günter Haufe Thieme Webshop de 2017-10-21 This unusual stability is attributed to delocalisation of electron density from the bond between the central carbon atoms onto the bridging carbon atoms.Sterling Alistair J. Dürr Alexander Smith Russell Anderson Edward Alexander Duarte Fernanda 2020-04-13 Rationalizing the diverse reactivity of [1.1.1]propellane through sigma-pi-delocalization Chemical Science 11 19 4895–4903 en 10.1039/D0SC01386B 34122945 8159217 2041-6539 free 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 [1.1.1]Propellane is a Charge-Shift Bond Angew. Chem. Int. Ed. 48 8 1407–1410 10.1002/anie.200804965 19072971 2009ACIE...48.1407W free Synthesis [1.1.1]Propellane was first reported by Kenneth B. Wiberg and F. Walker in 1982, according to the second line in the following scheme. Synthesis begins with conversion of the 1,3-di-carboxylic acid of bicyclo[1.1.1]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:K. B. Wiberg F. H. Walker 1982 [1.1.1]Propellane J. Am. Chem. Soc. 104 19 5239–5240 10.1021/ja00383a046 1982JAChS.104.5239W thumb|none|400px|Scheme 1. Synthesis of [1.1.1]propellane However, a much simplified synthesis was published by Szeimies.Johannes Belzner Uwe Bunz Klaus Semmler Günter Szeimies Klaus Opitz Arnulf-Dieter Schlüter etal Concerning the synthesis of [1.1.1]propellane Chem. Ber. 1989 122 2 397–398 10.1002/cber.19891220233 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.[1.1.1]Propellane Kathleen R. Mondanaro William P. Dailey 1998 10 658 75 98 v75p0098 The product was not isolated but kept in solution at −196 °C. Reactions Acetic acid addition [1.1.1]Propellane spontaneously reacts with acetic acid to yield a methylidenecyclobutane ester (4 above). Polymerization [1.1.1]Propellane undergoes a polymerization reaction where the central C–C bond is split and connected to adjacent monomer units, resulting in staffanes.Piotr Kaszynski Josef Michl 1988 [n]Staffanes: a molecular-size "Tinkertoy" construction set for nanotechnology. Preparation of end-functionalized telomers and a polymer of [1.1.1]propellane J. Am. Chem. Soc. 110 15 5225–5226 10.1021/ja00223a070 1988JAChS.110.5225K thumb|none|400px|Scheme 2. Synthesis of [n]staffane A radical polymerization initiated by methyl formate and benzoyl peroxide results in a distribution of oligomers. An anionic addition polymerization with n-butyllithium results in a fully polymerized product. X-ray diffraction of the polymer shows that the connecting C–C bonds have bond lengths of only 1.48 Å, significantly shorter than the normal 1.54 Å. The compound 1,3-dehydroadamantane, which can be viewed as a bridged [1.3.3]propellane, also polymerizes in a similar way. See also [2.2.2]Propellane Bicyclo[1.1.1]pentane which lacks a bond between the bridgehead carbons. References Category:Bicycloalkanes Category:Tricyclic compounds Category:Monomers