(iii) The bond fragilities introduced in previous works clearly deliver description of the anharmonic effects for all bonds/contacts in the reacting system. Here we demonstrate how the bond fragilities provide a unique measure of the anharmonic effects in the system, reflecting the response of the vibrational electronic energy to changes in the distances between atoms. The additive contributions from all bonds are combined to the unique global anharmonicity parameter, the third electron energy derivative over the reaction progress. This quantity can be used as a measure of the global changes in a molecule, when they are triggered step by step along a specific reaction path.