Reaction Mechanism of CO₂ and Styrene Oxide Catalyzed by Ionic Liquids: A Combined DFT Calculation and Experimental Study

Abstract

Bioactive compound 3-aryl-2-oxazolidinone could be synthesized by a green method mixing carbon dioxide, aniline, and ethylene oxide. Our group previously proposed a parallel mechanism for this conversion catalyzed by ionic liquids. Recently, a new study on a similar reaction system of styrene oxide, carbon dioxide, and aniline under the catalysis of K3PO4 gave a different serial mechanism. In order to explore the mechanism of reaction, we conducted a combined theoretical and experimental study on a one-pot conversion of styrene oxide, carbon dioxide, and aniline. In experiments, two isomer products, 3,5-diphenyl-l,3-oxazolidin-2-one and 3,4-diphenyl-l,3-oxazolidin-2-one, were observed. The computational results show that the parallel mechanism is more favored in thermodynamics and in kinetics due to the instability of isocyanate and hardness of its generation. Hence, we believe the previous parallel mechanism is more reasonable under our catalysts and conditions.

Trimetallic Oxide Foam as an Efficient Catalyst for Fixation of CO2 into Oxazolidinone: An Experimental and Theoretical Approach

“…In the oxazolidinone synthesis initially, CO 2 and PO molecule adsorption and activation steps are very crucial for the formation of intermediate species, namely, PC and PI, for the formation of the desired product . Based on the XRD profile of the PTOF catalyst, the observed intensity of the CuO plane was high compared to that of other metal oxides, namely, cobalt and nickel oxides.…”

“…In the next step, intermediate molecule, namely, PC and PI, adsorption and activation phases are very important in the successful formation of the desired product of oxazolidinone . The adsorbed PC molecule over the CuO(002) plane of the PTOF surface model is shown in Figure S17c.…”

“…The free energy values are calculated for four important steps in the oxazolidinone mechanism as follows (* indicates molecules interacting with the PTOF catalyst surface model) In the initial step, in the absence of interactions between molecules and the CuO(002) plane of the PTOF surface, free energy was calculated to be 0.0 eV . At the beginning of the oxazolidinone formation process, CO 2 and PO molecule adsorption and activation steps are very important for the formation of the first intermediate molecule of PC. , The activated CO 2 (BE = 0.56 eV, BA = 172.9°, BL = 2.42 Å) and PO (BE = 0.41 eV, BL = 2.27 Å) molecules correspondingly produced *CO 2 δ− (carboxylate) and *opened ring propylene oxide species on the CuO(002) plane of the PTOF surface. In the second step of the process, the first intermediate of PC was formed by an intermolecular cyclization process through stretching/breaking and formation of the new bonds between the obtained species of *CO 2 δ− and *opened ring propylene oxide .…”

“…67 In the next step, intermediate molecule, namely, PC and PI, adsorption and activation phases are very important in the successful formation of the desired product of oxazolidinone. 66 The adsorbed PC molecule over the CuO(002) plane of the PTOF surface model is shown in Figure S17c. The binding energy of the adsorbed PC molecule exhibited a value of 0.24 eV, and the bond length between the carbonyl carbon (C) of the PC molecule and oxygen site of the CuO(002) plane of the PTOF surface was 3.00 Å.…”

“…At the beginning of the oxazolidinone formation process, CO 2 and PO molecule adsorption and activation steps are very important for the formation of the first intermediate molecule of PC 11,66. The activated CO 2 (BE = 0.56 eV, BA = 172.9°, BL = 2.42 Å) and PO (BE = 0.41 eV, BL = 2.27 Å) molecules correspondingly produced *CO 2 δ− (carboxylate) and *opened ring propylene oxide species on the CuO(002) plane of the PTOF surface.…”