Heptane

From Academic Kids

**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 (http://en.wikipedia.org/wiki/Image:Heptane_HNMR.png) ¹³C NMR spectrum of n-heptane (http://en.wikipedia.org/wiki/Image:Heptane_CNMR.png)

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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