What Is the Chemical Reaction Equation for the Combustion of Octane?

By Staff WriterLast Updated Mar 25, 2020 9:44:56 AM ET

The chemical reaction equation for the combustion of octane (C8H18), which is one of the primary components of gasoline, is 2C8H18 + 25O2 —> 16CO2 + 18H2O. As the reaction equation illustrates, carbon dioxide gas is produced when octane is burned. This is typical of combustion reactions involving hydrocarbons, such as octane and propane.


In a basic combustion process, such as the burning of gasoline in a combustion engine, the reactants on the left-hand side of the chemical reaction equation consist of a hydrocarbon fuel and an oxidizer, which can be oxygen or air. The reactants are transformed by a chemical process into the products shown on the right-hand side of the chemical reaction equation. Because the energy that was holding the atoms together in the reactants has been released, the chemical reaction results in that energy being given off in the form of heat.

Octane is highly flammable and volatile, which are characteristics similar to the other low molecular weight hydrocarbons. The condensed structural formula for octane is CH3(CH2)6CH3, and it also belongs to the category of organic compounds called alkanes. Octane is a colorless, odorless liquid with a flash point of 55.4 degrees Fahrenheit. Because an octane rating was used as a selling point in gasoline advertisements, "high-octane" also became a figurative term used as an intensifier in colloquial American speech.