Illustrated Glossary of Organic Chemistry

Enthalpy of combustion (heat of combustion): The enthalpy change (ΔH) that occurs when a substance is combusted (i.e., burned) in an excess of oxygen. Can be used as a measure of molecular stability, for example, when measuring ring strain.

The enthalpy of combustion for n-octane is greater than the enthalpy of combustion for 2,2,3,3-tetramethylbutane. Therefore the linear C8H18 isomer is less stable than the branched C8H18 isomer.