So in general, why is that? Why is it that some isomers of alkans are more stable than other isomers of that same alkane? So we're going to address that question in this lecture. So let's begin by defining change in Enthalpy affirmation. So loosely speaking, enthalpy affirmation is the energy difference between the final product and its constituent elements. In other words, if this value is negative, that means our final products are stable or more stable than the constituent elements.