2,2,4-Trimethylpentane

Names
Preferred IUPAC name 2,2,4-Trimethylpentane[1]
Identifiers
CAS Number	540-84-1 Y
3D model (JSmol)	Interactive image
Beilstein Reference	1696876
ChEBI	CHEBI:62805 N
ChEMBL	ChEMBL1797261 N
ChemSpider	10445 Y
ECHA InfoCard	100.007.964
EC Number	208-759-1
MeSH	2,2,4-trimethylpentane
PubChem CID	10907
RTECS number	SA3320000
UNII	QAB8F5669O Y
UN number	1262
CompTox Dashboard (EPA)	DTXSID7024370
InChI InChI=1S/C8H18/c1-7(2)6-8(3,4)5/h7H,6H2,1-5H3 Y Key: NHTMVDHEPJAVLT-UHFFFAOYSA-N Y
SMILES CC(C)CC(C)(C)C
Properties
Chemical formula	C8H18
Molar mass	114.232 g·mol−1
Appearance	Colorless liquid
Odor	petroleum-like
Density	0.692 g cm−3
Melting point	−107.38 °C; −161.28 °F; 165.77 K
Boiling point	99.30 °C; 210.74 °F; 372.45 K
log P	4.373
Vapor pressure	5.5 kPa (at 21 °C)
Henry's law constant (kH)	3.0 nmol Pa−1 kg−1
UV-vis (λmax)	210 nm
Magnetic susceptibility (χ)	-98.34·10−6 cm3/mol
Refractive index (nD)	1.391
Thermochemistry
Heat capacity (C)	242.49 J K−1 mol−1
Std molar entropy (S⦵298)	328.03 J K−1 mol−1
Std enthalpy of formation (ΔfH⦵298)	−260.6 to −258.0 kJ mol−1
Std enthalpy of combustion (ΔcH⦵298)	−5462.6 to −5460.0 kJ mol−1
Hazards
GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H225, H304, H315, H336, H410
Precautionary statements	P210, P261, P273, P301+P310, P331
NFPA 704 (fire diamond)	1 3 0
Flash point	−12 °C (10 °F; 261 K)
Autoignition temperature	396 °C (745 °F; 669 K)
Explosive limits	1.1–6.0%
Related compounds
Related alkanes	2,2-Dimethylbutane 2,3-Dimethylbutane Triptane Tetramethylbutane Tetraethylmethane 2,3,3-Trimethylpentane 2,3,4-Trimethylpentane Tetra-tert-butylmethane 2,3-Dimethylhexane 2,5-Dimethylhexane
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

2,2,4-Trimethylpentane, also known as isooctane or iso-octane, is an organic compound with the formula (CH₃)₃CCH₂CH(CH₃)₂. It is one of several isomers of octane (C₈H₁₈). This particular isomer is the standard 100 point on the octane rating scale (the zero point is n-heptane). It is an important component of gasoline, frequently used in relatively large proportions (around 10%) to increase the knock resistance of fuel.^[2][3]

Strictly speaking, if the standard meaning of ‘iso’ is followed, the name isooctane should be reserved for the isomer 2-methylheptane. However, 2,2,4-trimethylpentane is by far the most important isomer of octane and historically it has been assigned this name.^[4]

Production

Isooctane is produced on a massive scale in the petroleum industry by alkylation of isobutene with isobutane. This process is conducted in alkylation units in the presence of acid catalysts.^[5]

It can also be produced from isobutylene by dimerization using an Amberlyst catalyst to produce a mixture of iso-octenes. Hydrogenation of this mixture produces 2,2,4-trimethylpentane.^[6]

History

Engine knocking is an unwanted process that can occur during high compression ratios in internal combustion engines. In 1926 Graham Edgar added different amounts of n-heptane and 2,2,4-trimethylpentane to gasoline, and discovered that the knocking stopped when 2,2,4-trimethylpentane was added. This work was the origin of the octane rating scale.^[7] Test motors using 2,2,4-trimethylpentane gave a certain performance that was standardized as 100 octane. The same test motors, run in the same fashion, using heptane, gave a performance which was standardized as 0 octane. All other compounds and blends of compounds then were graded against these two standards and assigned octane numbers.

Safety

In common with all hydrocarbons, 2,2,4-trimethylpentane is flammable.^[8]