The heat of hydrogenation is the enthalpy released when one mole of an alkene is hydrogenated to the corresponding alkane. It matters because, when a set of isomeric alkenes all give the same alkane, comparing their heats of hydrogenation reveals their relative stabilities: the more stable alkene starts from a lower energy and so releases less heat. This provides experimental evidence that more highly substituted double bonds are more stable.

氢化热是一摩尔烯烃被氢化为相应烷烃时放出的焓。它之所以重要,是因为当一组异构烯烃都生成同一种烷烃时,比较它们的氢化热可揭示其相对稳定性:越稳定的烯烃起始能量越低,因而放出的热越少。这为取代程度越高的双键越稳定提供了实验证据。