Kinetics of the reactions of 4-nitrochlorobenzene with substituted phenolsin the presence of potassium carbonate

The kinetics of 4-nitrochlorobenzene (4-NCB) reactions with substituted phe nols in the presence of potassium carbonate in N,N-dimethylacetamide was st udied. Depending substituents, the reactivity of the phenols is changed in the series 3-NO2 > 4-Cl > H > 4-Br > 3-CH3 > 3-NH2, which is consistent wit h the series of their acidity. The reaction rates satisfactorily correlate with the pK(a) values of the corresponding substituted phenols. Based on ki netic data (first-order and zero-order reactions with respect to phenol and 4-NCB. respectively, and the consistency of the reactivity and acidity of substituted phenols), the deprotonation of phenols is considered as the rat e-determining step of the overall reaction under the test conditions. A rea ction scheme was proposed for the synthesis of diaryl ethers in the presenc e of potassium carbonate. It involves a heterogeneous step of phenol deprot onation, which takes place on the surface of potassium carbonate, and a hom ogeneous step of the interaction of potassium phenolates with 4-NCB. Under the reaction conditions, the resulting bicarbonate decomposes with the form ation of potassium carbonate and with the release of carbon dioxide and wat er.