A Computational Analysis of the Reaction of SO 2 with Amino Acid Anions: Implications for Its Chemisorption in Biobased Ionic Liquids.

We report a series of calculations to elucidate one possible mechanism of SO 2 chemisorption in amino acid-based ionic liquids. Such systems have been successfully exploited as CO 2 absorbents and, since SO 2 is also a by-product of fossil fuels' combustion, their ability in capturing SO 2 has been assessed by recent experiments. This work is exclusively focused on evaluating the efficiency of the chemical trapping of SO 2 by analyzing its reaction with the amino group of the amino acid. We have found that, overall, SO 2 is less reactive than CO 2 , and that the specific amino acid side chain (either acid or basic) does not play a relevant role. We noticed that bimolecular absorption processes are quite unlikely to take place, a notable difference with CO 2 . The barriers along the reaction paths are found to be non-negligible, around 7-11 kcal/mol, and the thermodynamic of the reaction appears, from our models, unfavorable.