Figure illustrates the optimized total energy relationship among the aforementioned hydrocarbons relative to the total energy of NBA which exhibits the lowest total energy of all in this group. A small energy difference of approximately 1 eV between the NBD and QC isomer pair is entirely attributed to the chemical bonding and different configurations (rearrangements) of hydrocarbons. A similar pattern is observed for the PPL and NBN isomer pair. The total energy order of these hydrocarbons is as follows: NBA < NBN < PPL < NBD < QC (Note that the hydrocarbons have varying numbers of hydrogens except for the isomers). In an isomer pair, the fully saturated isomer exhibits higher energy and therefore is less stable. For example, QC with all saturated C-C bonds has higher energy than NBD; whereas PPL with saturated structure exhibits larger energy than its isomer NBN.