Aliphatic Amines: A Critical Analysis of the Experimental Enthalpies of Formation by Comparison with Theoretical Calculations

The accuracy of experimental data on enthalpies of formation and vaporization of aliphatic amines (primary, secondary, and tertiary amines, di-, tri-, and tetramines, and cycloalkylamines) was assessed by theoretical calculations. The gas-phase enthalpies of formation were calculated using the Gaussian 4 (G4) method combined with isodesmic reactions. Three amines, CH3NH2, CH3NHCH3, and (CH3)(3)N, were used as the main reference species in the isodesmic reactions; their experimental enthalpies of formation were recently revisited in the Active Thermochemical Tables. The enthalpies of vaporization were estimated by three group additivity and molecular electrostatic potential models and then were used to calculate the enthalpies of formation in the liquid state. When the deviations of experimental values from those provided by the theoretical methods were analyzed, a set of accurate and consistent values of enthalpy of formation of aliphatic amines was recommended for use in thermochemical calculations and as benchmarks for theoretical chemistry.