As we know, topological studies of some typical reactions
have been carried out by many authors [13–23]. The emphasis
of these studies was on the topological properties of the bonds
of reactants, transition states and products. Recently, a method
has been proposed to determine when the bond is broken or
formed by Zheng [23]. But no one mentioned the relative
variation trend between the breaking bond and the forming
bond along the reaction path. In this article, we proposed a
novel method to determine the relative variation trend between
the breaking bond and the forming bond along the reaction path
by topological studies. In addition, less is known about the
relationship between topological characteristics of electron
density distribution and the reaction energy. In this article,
according to the topological properties of the chemical bonds,
we proposed a simple method to judge that a reaction is
exothermic or endothermic.