This study focuses on determining the dissociation constants as well as other thermodynamic properties for four amines of importance in the area of CO2 capture, namely, 1,4-bis(3-aminopropyl) piperazine, 1,3-bis(aminomethyl)-cyclohexane, tris(2-aminoethyl) amine, and 1-amino-4-methylpiperazine. All experiments were done at atmospheric pressure and at seven temperatures in the range of 288.15-323.15 K. The dissociation constants (pK(a)s) were measured using a potentiometric titration. The van't Hoff equation was used to determine thermodynamic properties such as the enthalpy, entropy, and free energy (Delta H-0, Delta S-0, and Delta G(0)) based on the pK(a) values measured at different temperatures. In addition, Gaussian was used to help explain the influence that the tertiary amine has on the second pK(a) of 1-amino-4-methylpiperazine. The density functional theory (DFT) was used to optimize the geometries after each protonation step and calculate the bond lengths between the nitrogen to the proton, which can be used as a comparison of the pK(a) of the amines. pK(a) values for the four studied amines were also predicted using the Perrin-Dempsey-Serjeant (PDS) model.