Selective Oxidative Dimerization of p-Cresol in Water-Organic Solvent Two Phase Systems.

Abstract

Oxidative coupling reactions of p-cresol with iron (III) chloride in aqueous solution were carried out in the presence of ethyl acetate, chloroform and hexane. The major reaction products were the o-o dimer, o-p dimer and o-o trimer. The influence of organic solvents on the selectivity of o-o dimer production was examined. In all cases, selectivity was improved by the addition of organic solvent at any rate, since the trimerization was prevented. By organic solvents, the o-o dimer could be extracted in preference to the p-cresol monomer during reaction. The dimer was thus efficiently excluded from the aqueous oxidation system where the oxidizing agent, the Fe3+ ion, was present. Ethyl acetate was good for increasing selectivity. The conversion of p-cresol, however, drastically decreased with an increase in the volume of ethyl acetate, since not only the o-o dimer but p-cresol monomer as well were efficiently extracted. The influence of hexane addition on the conversion and product distribution was slight due to the low extraction ability for p-cresol and its oxidized products. When chloroform was added, selectivity was significantly increased with little decline in conversion. Although nearly all the o-o dimer was extracted by chloroform during reaction, the p-cresol monomer was more prone to exist in the aqueous phase in contrast to the system containing ethyl acetate.