Heptane
| General
|
| Molecular formula
| C7H16
|
| CAS number
| 142-82-5
|
| EC number
| 205-563-8
|
| Physical characteristics
|
| Appearance
| Colourless liquid
|
| Melting point
| 182 K (-91° Celsius)
|
| Boiling point
| 371 K (98° Celsius)
|
| Vapour density
| 3.5
|
| Vapour pressure
| 40 mm Hg at 20° Celsius
|
| Specific gravity
| 0.684
|
| Flash point
| -1° Celsius
|
| Explosion limits
| 1.1 - 7%
|
| Autoignition temperature
| 222° Celsius
|
| Spectral data
|
| NMR spectra
| 1H NMR spectrum of n-heptane
13C NMR spectrum of n-heptane
|
Heptane (also known as dipropyl methane, gettysolve-C or heptyl hydride) is an alkane hydrocarbon with the chemical formula CH3(CH2)5CH3. Heptane has nine isomers.
The isomer n-heptane (straight-chain heptane) has been selected as the zero point of the octane rating scale. It is undesirable in petrol, as it burns explosively, causing engine knocking, as opposed to branched-chain octane isomers, which burn more slowly and give better performance. Its choice for the zero point of the scale was due to the availability of very high purity n-heptane, unmixed with other isomers of heptane or other alkanes, distilled from the resin of Jeffrey Pine. Other sources of heptane and octane, produced from crude oil, contain a mixture of different isomers with greatly differing ratings, so do not give a precise zero point.
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