2,2,4-Trimethylpentane

2,2,4-Trimethylpentane
IUPAC name 2,2,4-Trimethylpentane
Other names Isooctane[citation needed] Neopentylpropane[citation needed]
Identifiers
CAS number	540-84-1 Y
PubChem	10907
ChemSpider	10445 Y
EC number	208-759-1
UN number	1262
MeSH	2,2,4-trimethylpentane
ChEBI	CHEBI:62805 Y
ChEMBL	CHEMBL1797261 Y
RTECS number	SA3320000
Beilstein Reference	1696876
Jmol-3D images	Image 1
SMILES CC(C)CC(C)(C)C
InChI InChI=1S/C8H18/c1-7(2)6-8(3,4)5/h7H,6H2,1-5H3 Y Key: NHTMVDHEPJAVLT-UHFFFAOYSA-N Y
Properties
Molecular formula	C8H18
Molar mass	114.23 g mol−1
Exact mass	114.140850576 g mol−1
Appearance	Colorless, transparent liquid
Odor	Odorless
Density	692 mg mL−1
Melting point	-107--107 °C, 165.71-165.83 K, -161--161 °F
Boiling point	99-99 °C, 372.2-372.6 K, 210-211 °F
log P	4.373
Vapor pressure	5.5 kPa (at 21 °C)
kH	3.0 nmol Pa−1 kg−1
λmax	210 nm
Refractive index (nD)	1.391
Thermochemistry
Std enthalpy of formation ΔfHo298	−260.6–−258.0 kJ mol−1
Std enthalpy of combustion ΔcHo298	−5462.6–−5460.0 kJ mol−1
Standard molar entropy So298	328.03 J K−1 mol−1
Specific heat capacity, C	242.49 J K−1 mol−1
Hazards
GHS pictograms
GHS signal word	DANGER
GHS hazard statements	H225, H304, H315, H336, H410
GHS precautionary statements	P210, P261, P273, P301+310, P331
EU Index	601-009-00-8
EU classification	F Xn N
R-phrases	R11, R38, R50/53, R65, R67
S-phrases	(S2), S16, S29, S33
NFPA 704	4 1 0
Flash point	−12 °C
Autoignition temperature	396 °C
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
Y (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

2,2,4-Trimethylpentane, also known as isooctane, 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 for 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 to increase the knock resistance of the fuel.

Production

Isooctane is produced on a massive scale in the petroleum industry by distillation of petroleum. 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.

Dimerization of isobutylene followed by hydrogenation produces 2,2,4-trimethylpentane

History

Engine knocking is an unwanted process that can occur during combustion in internal combustion engines. Graham Edgar in 1926 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 was the origin of the octane rating scale. The best anti-knock agent at an economical price is tetraethyllead, but because lead is very harmful to the environment, industry turned to MTBE. However, MTBE itself has caused controversy due to its relatively high solubility in water, which can in the event of a leak or spill result in serious contamination of groundwater, and as a result 2,2,4-trimethylpentane is still one of the most common anti-knock agents in wide use today.

Safety

In common with all hydrocarbons, inhalation or ingestion of large quantities of iso-octane is harmful. In rare cases a stronger reaction can occur. It is also flammable (as one would expect for a fuel).

See also

• Oil refinery
• Antiknock agents

External links

• International Chemical Safety Card 0496