2,2,4-Trimethylpentane

2,2,4-Trimethylpentane
Names
	IUPAC name 2,2,4-Trimethylpentane
Identifiers
CAS Number	540-84-1 ;
3D model (JSmol)	Interactive image;
Beilstein Reference	1696876
ChEBI	CHEBI:62805 ;
ChEMBL	ChEMBL1797261 ;
ChemSpider	10445 ;
ECHA InfoCard	100.007.964
EC Number	208-759-1;
MeSH	2,2,4-trimethylpentane
PubChem CID	10907;
RTECS number	SA3320000;
UNII	QAB8F5669O ;
UN number	1262
CompTox Dashboard (EPA)	DTXSID7024370 ;
	InChI InChI=1S/C8H18/c1-7(2)6-8(3,4)5/h7H,6H2,1-5H3 Key: NHTMVDHEPJAVLT-UHFFFAOYSA-N ;
	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 (So298)	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 pictograms
GHS Signal word	Danger
GHS hazard statements	H225, H304, H315, H336, H410
GHS precautionary statements	P210, P261, P273, P301+310, P331
NFPA 704 (fire diamond)	3 1 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).

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 to increase the knock resistance of the fuel.^[2]

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 so, historically, it has been assigned this name.^[3]

Production

Isooctane is produced on a massive scale in the petroleum industry by alkylation of isobutene with isobutane. The process is conducted in alkylation units in the presence of acid catalysts.^[4]

Route to 2,2,4-trimethylpentane from isobutene and isobutane

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.^[5]

History

Engine knocking is an unwanted process that can occur during high compression ratios 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 work was the origin of the octane rating scale.^[6] 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.^[7]

References

^ "2,2,4-trimethylpentane - Compound Summary". PubChem Compound. USA: National Center for Biotechnology Information. 26 March 2005. Identification and Related Records. Retrieved 11 March 2012.
^ Werner Dabelstein; Arno Reglitzky; Andrea Schütze; Klaus Reders (2007). "Automotive Fuels". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a16_719.pub2.
^ Clayden, Jonathan (2005). Organic chemistry (Reprinted (with corrections). ed.). Oxford [u.a.]: Oxford Univ. Press. pp. 315. ISBN 978-0-19-850346-0.
^ Bipin V. Vora; Joseph A. Kocal; Paul T. Barger; Robert J. Schmidt; James A. Johnson (2003). "Alkylation". Kirk‐Othmer Encyclopedia of Chemical Technology. doi:10.1002/0471238961.0112112508011313.a01.pub2.
^ Dimerization of isobutylene, Amberlyst.com
^ Fuels and lubricants handbook, Volume 1, George E. Totten, Steven R. Westbrook, Rajesh J. Shah, page 62
^ 2,2,4-Trimethylpentane, Integrated Risk Information System, United States Environmental Protection Agency

External links

International Chemical Safety Card 0496

[1] "2,2,4-trimethylpentane - Compound Summary". PubChem Compound. USA: National Center for Biotechnology Information. 26 March 2005. Identification and Related Records. Retrieved 11 March 2012.

[2] Werner Dabelstein; Arno Reglitzky; Andrea Schütze; Klaus Reders (2007). "Automotive Fuels". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a16_719.pub2.

[3] Clayden, Jonathan (2005). Organic chemistry (Reprinted (with corrections). ed.). Oxford [u.a.]: Oxford Univ. Press. pp. 315. ISBN 978-0-19-850346-0.

[4] Bipin V. Vora; Joseph A. Kocal; Paul T. Barger; Robert J. Schmidt; James A. Johnson (2003). "Alkylation". Kirk‐Othmer Encyclopedia of Chemical Technology. doi:10.1002/0471238961.0112112508011313.a01.pub2.

[5] Dimerization of isobutylene, Amberlyst.com

[6] Fuels and lubricants handbook, Volume 1, George E. Totten, Steven R. Westbrook, Rajesh J. Shah, page 62

[7] 2,2,4-Trimethylpentane, Integrated Risk Information System, United States Environmental Protection Agency

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