2,2,4-Trimethylpentane

2,2,4-Trimethylpentane, also known as isooctane, is an octane isomer which defines the 100 point on the octane rating scale. It is one of the compounds in petrol/gasoline and has an enthalpy of combustion of -48 kJ/g or -33 kJ/cm³.

Iso-octane, usually as a mixture with related hydrocarbons, is produced on a massive scale in the petrol industry. The alkylation process alkylates isobutane with isobutylene using an acid catalyst (sulfuric acid or hydrofluoric acid). In another process, NExOCTANE, isobutylene is dimerized into iso-octene and hydrogenated to iso-octane.