Reaction Mechanisms and Kinetics of the Melt Transesterification of Bisphenol‐A and Diphenyl Carbonate

Abstract

The catalyzed and uncatalyzed reaction mechanisms of the melt transesterification process of bisphenol‐A and diphenyl carbonate are proposed based on nucleophilic substitution at the carbonyl group of the reactants. The reaction paths and energy barriers of the melt transesterification reaction were predicted and identified via density functional theory (DFT) calculations. The calculations reveal that the different oligomers with only one repeating unit are formed through different thermal processes. The theoretical evaluation further indicates that the basic hydroxide catalysts can reduce the energy barrier for the transesterification reaction, which allows subsequent nucleophilic attack to easily occur. Furthermore, the reaction kinetics of transesterification using tetraethyl ammonium hydroxide as a catalyst were investigated experimentally over a temperature range of 155–175°C. The reaction rate constants and equilibrium constants were determined based on the functional group model, and the equilibrium constants decreased with increasing reaction temperature. A detailed molecular species model with a specific repeating unit (n = 3) was developed and applied to predict the change in the reactants, oligomers, and phenol, and the experimental data and model calculation agree quite well. The standard curves of the oligomer were reversely derived, which provide intuitive insight into the concentration change of each oligomer. Both the DFT calculations and experimental results indicate that the C1 oligomer is first formed, and some of which are then converted to other types or higher molecular weight oligomers.

Neighboring Group Participation and Internal Catalysis Effects on Exchangeable Covalent Bonds: Application to the Thriving Field of Vitrimer Chemistry

“…75 Bases are also common catalysts, for instance magnesium hydroxide, 76 calcium salts 77,78 or sodium alkoxides. 74,79 All the catalyzed mechanisms described are associative, 69,71,74,[76][77][78][79][80] though they are slightly different depending on the type of catalysis employed (Scheme 3).…”

“…The deprotonated counterpart (phenolate) is the reactive species toward the electrophilic carbon of the carbonate carbonyl moiety. The reaction proceeds through a tetrahedral intermediate before the elimination of a phenolate (from the starting carbonate or from the reactant). , However, this exchange is very slow . Transcarbonation is known to be catalyzed by metal-derived catalysts such as tin salts, − zinc acetate, copper salts, and even a dimetallic iron–manganese cyanide catalyst .…”

“…Transcarbonation is known to be catalyzed by metal-derived catalysts such as tin salts, − zinc acetate, copper salts, and even a dimetallic iron–manganese cyanide catalyst . Bases are also common catalysts, for instance, magnesium hydroxide, calcium salts, , or sodium alkoxides. , All the catalyzed mechanisms described are associative, ,,,− though they are slightly different depending on the type of catalysis employed (Scheme ).…”

Reaction kinetics of melt post‐polycondensation process for polycarbonate in film state

“…In our previous discussion, it was shown that the AMC‐catalyzed PC polycondensation system induces unfavorable branching structure related to the ability of the alkaline metal to bind several oxygen atoms simultaneously (see Section 3.1). For comparison, the QAH in Con‐A was considered as an efficient and steady catalyst to obtain high molecular weight PC with few side reactions 25,42 . Considering the larger ionic radius of QAH, and four phenyl groups increase the possibility of steric hindrance.…”

“…To produce a high molecular weight PC, it is necessary to add a suitable catalyst to the reaction system to improve its reaction rate. It has been reported that basic compounds such as alkali metals, 23 alkaline earth metals, 24 tetraethyl ammonium hydroxide 25 and others 26 show excellent catalytic performance in the synthesis of PC by melt transesterification process. However, little literature has been reported on the effect of catalysts for the MPP of PC.…”