Figure 1. Ball and stick model of heptane, the white balls represent hydrogen atoms and the black balls represent carbon atoms.[1]

Heptane is an alkane with the chemical formula C7H16. As a hydrocarbon, it can undergo hydrocarbon combustion which gives off heat energy. Heptane is a volatile, colourless liquid that is odourless when pure.[2]

Heptane is an important hydrocarbon (or organic molecule as it, along with pure octane, sets the extreme ends of the octane rating scale. Heptane is used to set the standard zero point. This means that as a fuel it burns in a way that is unhelpful within an engine, specifically, it combusts when put under pressure. This is why higher octane ratings are better for an engine. Heptane is a terrible fuel choice for a car since it burns explosively, causing engine knocking. As well as setting the zero point for octane rating, heptane is frequently used as a laboratory solvent due to it's low reactivity with other molecules. Many substances that will not dissolve in water do dissolve in heptane.[3]


Below is a table of some of the basic properties of heptane.

Chemical formula C7H16
Molar mass 100.21 grams/mole
Melting point -91oC[4]
Boiling point 98oC[4]

Combustion Reaction

Heptane undergoes hydrocarbon combustion, combining with oxygen to form carbon dioxide. The balanced chemical equation for the complete combustion of heptane is:

C7H16 + 11O2 → 7CO2 + 8H2O + Heat Energy (Enthalpy)

The hydrocarbon combustion reaction releases heat energy and is an example of an exothermic reaction. The reaction also has a negative enthalpy change (ΔH) value.

For Further Reading


  1. "Heptane-3D-balls". Licensed under Public Domain via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Heptane-3D-balls.png#mediaviewer/File:Heptane-3D-balls.png
  2. National Center for Biotechnology Information. (2015). Properties of Heptane [Online]. Available: http://pubchem.ncbi.nlm.nih.gov/compound/heptane [February 16,2015].
  3. Education Portal. (2015). Heptane: Structure, Uses, & Formula [Online]. Available: http://education-portal.com/academy/lesson/heptane-structure-uses-formula.html [February 16, 2015]
  4. 4.0 4.1 Charles E. Ophardt. (2003). Virtual Chembook - Hydrocarbon Boiling Points [Online]. Available: http://www.elmhurst.edu/~chm/vchembook/501hcboilingpts.html [February 16,2015].