a b s t r a c t We use the derivative of the electron density with respect to the reaction coordinate, interpreted through the Berlin binding function, to identify portions of the reaction path where chemical bonds are breaking and forming. The results agree with the conventional description for S N 2 reactions, but they are much more general and can be used to elucidate other types of reactions also. Our analysis offers support for, and detailed information about, the use of the reaction force profile to separate the reaction coordi-nates into intervals, each with characteristic extents of geometry change and electronic rearrangement. Ó 2012 Elsevier B.V. All rights reserved.