2,2,4-Trimethylpentane: Difference between revisions
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Revision as of 05:43, 5 November 2010
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| Names | |
|---|---|
| IUPAC name
2,2,4-Trimethylpentane
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| Other names
Isooctane
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| Identifiers | |
3D model (JSmol)
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| ChemSpider | |
| ECHA InfoCard | 100.007.964 |
| RTECS number |
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CompTox Dashboard (EPA)
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| Properties | |
| C8H18 | |
| Molar mass | 114.232 g·mol−1 |
| Appearance | colorless liquid |
| Density | 688 kg/m3, liquid |
| Melting point | −107.38 °C (−161.28 °F; 165.77 K) |
| Boiling point | 99.3 °C (210.7 °F; 372.4 K) |
| Immiscible | |
| Thermochemistry | |
Std molar
entropy (S⦵298) |
328 J·K−1·mol−1 |
Std enthalpy of
formation (ΔfH⦵298) |
−259 kJ/mol |
Std enthalpy of
combustion (ΔcH⦵298) |
−5461 kJ/mol |
| Hazards | |
| NFPA 704 (fire diamond) | |
| Flash point | 4.5 °C |
| Explosive limits | 1.1–6.0% |
| Related compounds | |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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2,2,4-Trimethylpentane, also known as isooctane, iso-octane or rarely neopentylpropane, is an octane isomer which defines the 100 point on the octane rating scale (the zero point is n-heptane). It is an important component of gasoline.
Isooctane is produced on a massive scale in the petroleum industry, usually as a mixture with related hydrocarbons. The alkylation process alkylates isobutane with isobutylene using a strong acid catalyst. In the NExOCTANE process, isobutylene is dimerized into isooctene and then hydrogenated to isooctane.[1]
Hazards
This compound is hazardous to the human body. When 2,2,4-trimethylpentane is inhaled it can cause confusion, dizziness, headaches, nausea, and severe vomiting. If the substance comes into contact with human skin it can cause the area to become dry, turn red, and become extremely painful. A study was done on the long term exposure to isooctane in male rats. The study showed that it caused kidney damage, altered renal functions and a higher production of alpha2uglobulin protein.[2] It is also flammable.
Synthesis
2,2,4-Trimethylpentane is synthesized industrially from isobutylene. Isobutylene is first dimerized using an Amberlyst catalyst to produce a mixture of iso-octenes. Hydrogenation of this mixture produces 2,2,4-trimethylpentane.[3]
Dimerization of isobutylene followed by hydrogenation produces 2,2,4-trimethylpentane
Uses
Engine knocking is an unwanted process that can occur during combustion in internal combustion engines. In 1919 Charles Kettering and Thomas Midgley, Jr. began experimenting with different compounds to identify the source of the knocking, and how to stop it. After several tests they discovered a compound called tetraethyllead. 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.[4]
The best anti-knock agent at an economical price is tetraethyllead, but because lead is very harmful to the environment, and other compounds are expensive and have other drawbacks, the gasoline manufacturers were forced to go back to using 2,2,4-trimethylpentane. Many anti-knock agents have been manufactured but 2,2,4-trimethylpentane is still the most widely used.[5]
Experiments have been done to see the effect of pressure on 2,2,4-trimethylpentane mobility of electrons. The mobility increased at room temperature with high pressures and decreased with the same pressure but high temperatures.[6]
See also
References
- ^ NExOCTANE - Neste Jacobs
- ^ 2,2,4-Trimethylpentane, Integrated Risk Information System, United States Environmental Protection Agency
- ^ Dimerization of isobutylene, Amberlyst.com
- ^ Fuels and lubricants handbook, Volume 1, George E. Totten, Steven R. Westbrook, Rajesh J. Shah, page 62
- ^ Carbon Hooch, Scientific American, May 22, 2006
- ^ Casanovas, J; Grob, R; Grelot, D; Blanc, D; Mathieu, J (1979). "Electron mobilities and rate constants for electron-solute reactions in some non polar liquids". Journal of Electrostatics. 7: 227. doi:10.1016/0304-3886(79)90074-3.