Phenol alkylation under phase transfer catalysis conditions: Insights on the mechanism and kinetics from computations

Experiments reported in the literature involving alkylation of the phenol under phase transfer catalysis conditions support the formation of the RN4+PhO?(PhOH) complex in the organic phase. This complex could be directly involved in the transition state. In the present theoretical study, the phase transfer catalyzed alkylation of phenol was investigated using M06-2X calculations and solvent effect using the SMD model combined with reliable experimental single-ion solvation free energy data in aqueous solution. The analysis was done for tetraethylammonium, tetrapropylammonium and tetrabutylammonium phase transfer catalysts. In the case of tetrabutylammonium ion, the calculations have predicted a reaction kinetics compatible with experimental data. In addition, the BuN4+PhO?(PhOH) complex is calculated to be the active species in the catalysis. For the tetraethylammonium and tetrapropylammonium cations, both the RN4+PhO? and RN4+PhO?(PhOH) complexes are not able to explain the catalysis, suggesting that another more complex aggregate can be involved in the process.

Automated summary

The study investigated the mechanism and active species of phase transfer catalyzed alkylation of phenol through calculations and modeling, revealing that the tetrabutylammonium ion complex is the active species in the catalysis. However, for the tetraethylammonium and tetrapropylammonium cations, another more complex aggregate may be involved in the process.