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.