Theoretical insight into dimethyl carbonate carboxymethylation of alcohols assisted by Lewis acid proton carrier catalyst FeCl3

Abstract

To extend the understanding of role of Lewis acid catalysts in dimethyl carbonate (DMC) chemistry, density functional theory (DFT) calculation is conducted to demonstrate the mechanism of DMC mediated carboxymethylation of ethanol catalysed by FeCl3. In parallel with the investigation based on transition state theory (TST), the nature of bonding of all studied species and bonding evolution along the optimal reaction pathways is explored via the topological analysis of electron localization function (ELF) and atoms in molecules (AIM) theory. Results indicate that hydrogen bond among alcohols promotes the molecules to form cyclic transition state, which facilitates reaction in the absence of catalyst. Additionally, FeCl3, acts as a Lewis acid proton carrier catalyst, is proved to reduce the reaction activation energy significantly. Finally, the calculated turnover frequency (TOF) of FeCl3 pathway relative to catalyst-free is 4.06 × 105, providing evidence that FeCl3 is an efficient catalyst for DMC chemistry.