Study of the Carbamate Stability of Amines Using ab Initio Methods and Free-Energy Perturbations

The relative carbamate stability of a series of amines used in CO2 absorption processes have been studied with different solvation models and gas-phase energies calculated with the B3LYP density functional method. The solvation energies were calculated with Monte Carlo free-energy perturbations and continuum models. Comparison between calculated energies and experimental nuclear magnetic resonance (NMR) and kinetic data shows reasonable agreement. The trends in carbamate stability apparently cannot be explained, in terms of any single molecular characteristic.