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Preferred IUPAC name Spiro[2.2]pentane | |
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Properties | |
C5H8 | |
Molar mass | 68.119 g·mol−1 |
Melting point | −134.6 °C (−210.3 °F; 138.6 K) |
Boiling point | 39.0 °C (102.2 °F; 312.1 K) |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). |
Spiropentane is a hydrocarbon with formula C5H8. It is the simplest spiro-connected cycloalkane, a triangulane. [1] [2] [3] [4] It took several years after the discovery in 1887 until the structure of the molecule was determined. [5] [6] [7] According to the nomenclature rules for spiro compounds, the systematic name is spiro[2.2]pentane. However, there can be no constitutive isomeric spiropentanes, hence the name is unique without brackets and numbers.
After Gustavson produced cyclopropane by reacting 1,3-dibromopropane with ground-up zinc metal, he tried the same reaction with 2,2-bis(bromomethyl)-1,3-dibromopropane (see formula scheme). The starting material is easily obtained by reacting pentaerythritol with hydrobromic acid. A molecule with the formula C5H8 was obtained. It was called vinyltrimethylene in the initial publication. [8] In 1907, Fecht expressed the assumption that it must be spiropentane, a constitutional isomer of vinylcyclopropane. [9] Further evidence for the structure of the hydrocarbon comes from the fact that it could also be obtained from 1,1-bis(bromomethyl)-cyclopropane (see formula scheme). [10]
Spiropentane is difficult to separate from the other reaction products and the early procedures resulted in impure mixtures. Decades later, the production method was improved. The spiro hydrocarbon can be separated from the byproducts (2-methyl-1-butene, 1,1-dimethylcyclopropane, methylenecyclobutane) by distillation. [11]
Structural determination by electron diffraction showed two different C-C lengths; the bonds to the quaternary ("spiro") carbon atom are shorter (146.9 pm) than those between the methylene groups (CH2–CH2, 151.9 pm). The C–C–C angles on the spiro C atom are 62.2°, larger than in cyclopropane. [12]
When heating molecules of spiropentane labelled with deuterium atoms, a topomerization or "stereomutation" reaction is observed, similar to that of cyclopropane: cis-1,2-dideuteriospiropentane equilibrates with trans-1,2-dideuteriospiropentane. [13]
Gustavson (1896) reported that heating spiropentane to 200 °C caused it to change into other hydrocarbons. A thermolysis in the gas phase from 360 to 410 °C resulted in ring expansion to the constitutional isomer methylenecyclobutane, along with the fragmentation products ethene and propadiene. [14] Presumably, the longer – and weaker – bond is broken first, forming a diradical intermediate. [13]
In organic chemistry, a carbene is a molecule containing a neutral carbon atom with a valence of two and two unshared valence electrons. The general formula is R−:C−R' or R=C: where the R represents substituents or hydrogen atoms.
Clemmensen reduction is a chemical reaction described as a reduction of ketones or aldehydes to alkanes using zinc amalgam and concentrated hydrochloric acid (HCl). This reaction is named after Erik Christian Clemmensen, a Danish-American chemist.
The Bischler–Möhlau indole synthesis, also often referred to as the Bischler indole synthesis, is a chemical reaction that forms a 2-aryl-indole from an α-bromo-acetophenone and excess aniline; it is named after August Bischler and Richard Möhlau .
The Ullmann reaction or Ullmann coupling, named after Fritz Ullmann, couples two aryl or alkyl groups with the help of copper. The reaction was first reported by Ullmann and his student Bielecki in 1901. It has been later shown that palladium and nickel can also be effectively used.
The Wurtz–Fittig reaction is the chemical reaction of an aryl halide, alkyl halides, and sodium metal to give substituted aromatic compounds. Following the work of Charles Adolphe Wurtz on the sodium-induced coupling of alkyl halides, Wilhelm Rudolph Fittig extended the approach to the coupling of an alkyl halide with an aryl halide. This modification of the Wurtz reaction is considered a separate process and is named for both scientists.
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Cobalt tetracarbonyl hydride is an organometallic compound with the formula HCo(CO)4. It is a volatile, yellow liquid that forms a colorless vapor and has an intolerable odor. The compound readily decomposes upon melt and in absentia of high CO partial pressures forms Co2(CO)8. Despite operational challenges associated with its handling, the compound has received considerable attention for its ability to function as a catalyst in hydroformylation. In this respect, HCo(CO)4 and related derivatives have received significant academic interest for their ability to mediate a variety of carbonylation (introduction of CO into inorganic compounds) reactions.
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Jakob Edmund Speyer was a high-ranking German university lecturer and chemist of Jewish descent. He was persecuted during the National Socialist era, losing his profession and his livelihood. He was deported to the Lodz ghetto, where he died in 1942.
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Millicent Taylor FRSC MSc DSc was a chemist who, in 1904, was one of the nineteen women who petitioned to join the Chemical Society
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