A DFT study on the insertion of CO2 into styrene oxide catalyzed by 1-butyl-3-methyl-Imidazolium bromide ionic liquid

Green systems able to capture or fix CO(2) are becoming more important specially to reduce environmental impacts. In this work, the mechanism of insertion of CO(2) into styrene oxide (STYO) both in the absence and presence of the catalyst 1-butyl-3-methyl-imidazolium bromide (BMIm Br) was investigated through calculations based on density functional theory in the ωB97X-D level. Two different routes were considered and it was shown they are energetically available and compete against each other. For both routes, the rate-determinant step is the ring opening of STYO resulting from the nucleophilic attack of the Br(-) on the C atom from STYO and is associated mainly to the participation of the cation and the anion from the catalyst in the reaction. Reactive indices and noncovalent interaction analysis were used as a tool to investigate this reason. This work allowed a better comprehension of the underlying mechanism and the supplied data provide valuable support for the design of new more efficient ionic liquid catalyst.