Science Fair Project Encyclopedia
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 |
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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