A theoretical study of two different mechanisms for the spontaneous deamination of cytosine is presented. In the first mechanism, a tetrahedral intermediate results in a two-step mechanism whereas in the second one, it is the result of a concerted step. In this work a link is made between the two pathways through the study of the evolution along the reaction coordinates of chemical concepts such as chemical potential, hardness and electronic populations within the framework of the reaction force analysis. The reaction force profile suggests that the concerted mechanism is composed of two asynchronous events. The observation of the reaction force profile appears as an easy way to identify asynchronous concerted steps and as a privileged tool to study the more or less asynchronous character of chemical reactions.