We present a theoretical study of global and local energetic and electronic properties to rationalize the formation process of molecular aggregates of acetic acid. Total energy, electronic chemical potential (mu), hardness (eta), and softness (S) are determined as a function of the size of the aggregate. We show that mu, eta, and S are observable properties to indicate structural changes occurring along the aggregation process. From the local point of view, the hydrogen bonding is characterized by making use of the energy and softness (SOH) associated with that interaction. In relation to the determination of S-O ... H we propose an analytic form to obtain the hydrogen bonding fukui function. The excellent results obtained indicate that our model is useful for characterizing local intermolecular interactions and provides a starting point to determine indexes of local reactivity in these molecular systems. A global and local Principle of Minimum Softness is shown to be occurring when the aggregate is growing.