LIQUID-PHASE ALKYLTHIOLATION REACTION OF PHENOL BY DIMETHYLDISULFIDE OVER ZEOLITES

The alkylthiolation reaction of phenol by dimethyldisulfide has been s tudied over various zeolites, in toluene as solvent. Over faujasite-ty pe zeolites, this reaction leads to the formation of 2-(methylthio)phe nol and 4-(methylthio)phenol with an initial ortho/para ratio in favor of the para isomer. Such a ratio changes with time; moreover, side re actions, mainly disubstitution and isomerisation of the para into the ortho derivative, are observed consecutively to the monosubstitution r eaction. The role of the composition of the initial reaction mixture h as been shown to be essential in the orientation of the reaction. A la rge excess of phenol leads to a decrease in the rates of the side reac tions, and the monosubstitution step can be oriented towards the predo minant formation of either the para or the ortho isomer, depending on the excess of phenol used. Such results are interpreted in terms of th e competitive adsorption of the two reactants on the catalyst.