DFT investigation for the mechanisms of γ-butyrolactones from styrene and acrylic acid, catalyzed by NMA*BF4 and PhSSPh

Abstract

The reaction mechanisms of γ-butyrolactones through electrophilic addition reactions between styrene and acrylic acid, catalyzed by the 9-mesityl-10-methylacridinium ion (NMA*BF4) and diphenyl disulfide (PhSSPh) under 450 nm visible-light, were investigated by employing M06-2X-D3/ma-def2SVP method and basis set. In this study, the SMD model was taken to simulate the solvent effect of dichloromethane. The photocatalyst NMA absorbs the energy of photons and becomes an excited state, capturing an electron from styrene; this leads to an electrophilic addition reaction happened between the obtained styrene cationic radical and acrylic acid anion (or acrylic acid molecule); finally, an intramolecular ring-closure process and H-shift process result in the formation of the final product. The computational results point out that the electrophilic reaction is an exothermic process; and the optimal path for ring-closure reaction and H-shift reaction has Gibbs free energy barriers of 11.10 and 9.94 kcal/mol, respectively. In particular, the recycling of the photo-catalyst NMA and cocatalyst PhSSPh has also been discussed. The ρhole and ρele can reveal the charge transfer process during the photo-catalytic reaction. Results would provide valuable insights into these types of interaction and related processes.