The kinetics and mechanism of polymer‐based NHC‐Pd‐pyridine catalyzed heterogeneous Suzuki reaction in aqueous media

Abstract

One of the most important challenges of the Suzuki reaction is a green synthesis of reaction products. In terms of economy and ecology, the Suzuki reaction details must be characterized for the industrial‐scale Suzuki reaction processes. In this paper, for the first time, a kinetic and mechanistic study on the Suzuki reaction catalyzed with hydrogel‐supported PEPPSI (pyridine‐enhanced precatalyst preparation stabilization (and) initiation) type NHC‐Pd‐pyridine composite has been investigated. To determine the rate‐limiting step, the effects of reactants and experimental conditions on the heterogeneous Suzuki reaction have been experimentally defined. The experimental results demonstrated that it is possible to reach 100% yield under the optimum reaction conditions, which were found as 75 × 10−3 mol/L of phenylboronic acid (FBA), 50 × 10−3 mol/L of bromoacetophenone (Brac), 125 × 10−3 mol/L of K2CO3, 1 g/L of catalyst, 80°C of reaction temperature, 400 rpm of mixing rate, and 3 h of reaction time. The transmetalation step in the cycle was defined as the rate‐limiting step. On the basis of kinetic results, a mathematical reaction rate expression was presented assuming the steady‐state approach to steps of the catalytic cycle. The activation energy (Ea) of the reaction was estimated to be 34.88 kJ/mol.

Kinetic Study of the Herrmann–Beller Palladacycle-Catalyzed Suzuki–Miyaura Coupling of 4-Iodoacetophenone and Phenylboronic Acid

“…The activation energy is similar to that obtained from initial rates. This value is in the range of what was published, as depicted in the introductory section [23,24,26].…”

“…The quantitative temperature effect on the SM reaction was reported only in two very recent papers. A global activation energy of 35 kJ/mol was determined for a polymer-based NHC-Pd-pyridine catalyst in aqueous media for the coupling of bromoacetophenone with phenylboronic acid [23] and 50 ± 5 kJ/mol for the coupling of bromoanisole with phenylboronic acid for a water-soluble palladium-β-cyclodextrin catalyst [24]. In the later, the absence of mixing and mass transfer issues was checked.…”

Micelle-Derived Palladium Nanoparticles for Suzuki–Miyaura Coupling Reactions in Water at Room Temperature

“…The first step of the Suzuki cross-coupling reaction, i.e., the oxidative addition of iodobenzene to Pd 0 resulting in a phenylpalladium(II)iodide complex, was the ratedetermining step. 75,76 In addition, because iodobenzene was considerably solubilized in the micellar core relative to Pd, the iodobenzene concentration could be regarded as constant, which was the reason we speculated zero-order kinetics of the reaction with respect to iodobenzene.…”

Prediction of Biomass Pyrolysis Mechanisms and Kinetics: Application of the Kalman Filter

“…Although understanding the reaction mechanisms is of utmost importance for process optimization and reactor design, the measurement techniques fall short of all the variables in these kinds of dynamic processes [23][24][25]. It is also relatively difficult to experimentally investigate the reversibility of the pyrolysis reactions, while it may be one of the crucial steps for a better definition of the biomass pyrolysis reactions.…”