V. V. Kopeikin

Kinetics of the Reactions of 4-Nitrochlorobenzene with Substituted Phenolates in an Aprotic Polar Solvent

The kinetics of 4-nitrochlorobenzene reactions with substituted phenolates in the medium of N,N-dimethylacetamide was studied. The BrØnsted relation is fulfilled by substituted potassium phenolates: the nucleophilicity of phenolates increases with an increase in their basicity. The rate-limiting step in the reactions of 4-nitrochlorobenzene with substituted phenolates and potassium resorcinate is changed from the phenoxide anion to the phenoxide dianion. In the latter case, electron transfer from the resorcinate dianion with the generation of radical species can be responsible for the reaction rate.

Kinetics of the Reactions of 4-Nitrochlorobenzene with Substituted Phenols in the Presence of Potassium Carbonate

The kinetics of 4-nitrochlorobenzene (4-NCB) reactions with substituted phenols in the presence of potassium carbonate in N,N-dimethylacetamide was studied. 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 with the series of their acidity. The reaction rates satisfactorily correlate with the pKavalues of the corresponding substituted phenols. Based on kinetic 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 rate-determining step of the overall reaction under the test conditions. A reaction scheme was proposed for the synthesis of diaryl ethers in the presence of potassium carbonate. It involves a heterogeneous step of phenol deprotonation, which takes place on the surface of potassium carbonate, and a homogeneous step of the interaction of potassium phenolates with 4-NCB. Under the reaction conditions, the resulting bicarbonate decomposes with the formation of potassium carbonate and with the release of carbon dioxide and water.