The Importance of Contributions of Conformations to the Radiative Forcing Value of a Compound Compared to the Lowest Energy Conformer using Quantum Chemistry

Abstract

This work evaluated a perfluorocarbon, perfluorobutylbutylmethylamine (PFBBM), to calculate all conformers that can possibly exist to investigate the effects of including non-minima energy conformers in a radiative forcing calculation. Principles of quantum chemistry were applied through Gaussian16 software to evaluate the thermodynamic properties of each conformer, such as the electronic energies, entropies, and vibrational frequencies. From this, the Gibb’s free energies were calculated in order to figure out, through the equilibrium constants, the percentage of time that these different conformers will exist relative to each other in the atmosphere. The narrowband model was applied to determine the individual radiative forcing value of each conformer. We also tested the importance of applying the hindered rotor correction versus not including this correction, as PFBBM has many possible internal rotations. We used this information to calculate a weighted radiative forcing, using the relative percentage of time that each conformer exists as the weighting factor, applied to the individual radiative forcing values of each conformer.