Diisobutene (also known as
Diisobutylene and
Isooctene) refers to a pair of
with the overall formula C
8H
16. 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 catalysis dimerization of
isobutene, a reaction that proceeds via the carbocation . The process also leads to some triisobutenes and tetraisobutenes.
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.
! align="center" colspan="5" | Diisobutene isomers |
| Image | | | 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
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
.
The isononylol (3,5,5-trimethyl-hexan-1-ol) is a precursor to 3,5,5-trimethylhexyl acetate, a commercial fragrance.
See also
-
1-Octene - the corresponding linear alpha-olefin
