Diisobutene
Diisobutene (also known as Diisobutylene and Isooctene) refers to a pair of organic compounds with the overall formula C8H16. The isomers have the same carbon skeleton but differ in the location of the C=C bond. Both are colorless liquids with very similar physical properties. These compounds arise via the acid catalyzed dimerization of isobutene, a reaction that proceeds via the carbocation (CH3)3C+. The process also leads to some triisobutenes and tetraisobutenes.[1] The commercial material is typically a mixture of isomers, with the terminal 1-ene being the major component. The preferential formation of the less substituted alkene can be counterintuitive to chemists, but can be explained by assessing its transition state.[2]
| Diisobutene isomers | ||||
|---|---|---|---|---|
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Mixed isomers | |
| Structure | CH2=C(CH3)-CH2C(CH3)3 | (CH3)2C=CHC(CH3)3 | ||
| Systematic name | 2,4,4-Trimethyl-1-pentene | 2,4,4-Trimethyl-2-pentene | 2,4,4-trimethylpentene | |
| CAS number | [107-39-1] | [107-40-4] | [25167-70-8] | |
| Density | 0.7150 g/mL | 0.7218 g/mL | 0.717 g/mL | |
| Melting point | -93.5 °C | -106.3 °C | -50 °C | |
| Boiling point | 101.4 °C | 104.9 °C | 102 °C | |
Applications
[edit]Hydrogenation is performed at a significant scale to give isooctane, which is an important fuel additive. Diisobutene is used as precursors to isononylol and octylphenols by hydroformylation/hydrogenation and phenol alkylation, respectively. Both are precursors to plasticizers.[3] The isononylol (3,5,5-trimethyl-hexan-1-ol) is a precursor to 3,5,5-trimethylhexyl acetate, a commercial fragrance.[4]
See also
[edit]- 1-Octene - the corresponding linear alpha-olefin
References
[edit]- ^ Schmidt, Roland; Griesbaum, Karl; Behr, Arno; Biedenkapp, Dieter; Voges, Heinz-Werner; Garbe, Dorothea; Paetz, Christian; Collin, Gerd; Mayer, Dieter; Höke, Hartmut (2014). "Hydrocarbons". Ullmann's Encyclopedia of Industrial Chemistry. pp. 1–74. doi:10.1002/14356007.a13_227.pub3. ISBN 978-3-527-30673-2.
- ^ Schuster, Mariah L.; Peterson, Karl P.; Stoffregen, Stacey A. (12 June 2018). "Isobutylene Dimerization: A Discovery-Based Exploration of Mechanism and Regioselectivity by NMR Spectroscopy and Molecular Modeling". Journal of Chemical Education. 95 (6): 1040–1044. doi:10.1021/acs.jchemed.7b00453.
- ^ Geilen, Frank M.A.; Stochniol, Guido; Peitz, Stephan; Schulte-Koerne, Ekkehard (2014). "Butenes". Ullmann's Encyclopedia of Industrial Chemistry. pp. 1–13. doi:10.1002/14356007.a04_483.pub3. ISBN 978-3-527-30385-4.
- ^ Panten, Johannes; Surburg, Horst (2015). "Flavors and Fragrances, 2. Aliphatic Compounds". Ullmann's Encyclopedia of Industrial Chemistry. pp. 1–55. doi:10.1002/14356007.t11_t01. ISBN 978-3-527-30673-2.