Oxidation of cumene with 1-methyl-1-phenylethyl hydroperoxide in the presence of copper chloride/phase transfer catalytic systems was investigated by ESI–MS. For catalytically active copper(II) chloride/crown ethers, copper(II) chloride/crown ethers/alkaline metal salts, and copper(II) chloride/tetrabutylammonium chloride systems, the presence of a few kinds of copper complexes in the organic phase was detected by use of ESI–MS. When copper(II) chloride/podand systems were used, the conversion of hydroperoxide and the yield of oxidation product were close to zero, although the concentration of copper complexes in the organic phase was high. Addition of bis(2-hydroxyethyl) ether to the catalytically active copper(II) chloride/18-crown-6 system resulted in an inhibition effect.
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