The work presents a method for calculating the thermodynamic potentials (free Gibbs energy, enthalpy, and entropy) and an analysis of the contributions of changes in translational, rotational, and vibrational degrees of freedom to the energy characteristics of the dimerization of aromatic compounds. On the whole, changes in the Gibbs energy caused by these contributions were shown to exceed the experimental energies of dimerization in solution in magnitude, which was evidence of the necessity of taking them into account for the aggregation of molecules. We determined changes in the Gibbs energy and entropy of translational, rotational, and vibrational (mechanical) degrees of freedom and the enthalpy of vibrations, which can be used to analyze the energy characteristics of dimerization reactions. These dimerization energy components should be calculated separately for each compound.