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
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 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

• 1-Octene - the corresponding linear alpha-olefin