| 2,2,4-Trimethylpentane | |
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2,2,4-Trimethylpentane |
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Other names
Isooctane, neopentylpropane (rare) |
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| Identifiers | |
| CAS number | 540-84-1 |
| ChemSpider | 10445 |
| RTECS number | SA3320000 |
| Jmol-3D images | Image 1 |
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| Properties | |
| Molecular formula | C8H18 |
| Molar mass | 114.23 g mol−1 |
| Appearance | colorless liquid |
| Density | 688 kg/m3, liquid |
| Melting point |
-107.38 °C, 166 K, -161 °F |
| Boiling point |
99.3 °C, 372 K, 211 °F |
| Solubility in water | Immiscible |
| Thermochemistry | |
| Std enthalpy of formation ΔfH |
−259 kJ/mol |
| Std enthalpy of combustion ΔcH |
−5461 kJ/mol |
| Standard molar entropy S |
328 J·K−1·mol−1 |
| Hazards | |
| MSDS | MSDS |
| EU classification | Flammable (F) Harmful (Xn) Dangerous for the environment (N) |
| R-phrases | R11 R38 R50/53 R65 R67 |
| S-phrases | (S2) S9 S16 S29 S33 S60 S61 S62 |
| NFPA 704 |
4
1
0
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| Flash point | 4.5 °C |
| Autoignition temperature |
417 °C |
| Explosive limits | 1.1–6.0% |
| Related compounds | |
| Related alkanes | Heptane Octane |
| Related compounds | Hexadecane |
| (verify) (what is: /?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) |
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| 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.[1]
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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.[2]
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.[3] The best anti-knock agent at an economical price is tetraethyllead, but because lead is very harmful to the environment, industry turned to MTBE.
In common with all hydrocarbons, inhalation or ingestion of large quantities of iso-octane is harmful. In rare cases a stronger reaction can occur.[4] It is also flammable (as one would expect for a fuel).
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