ChemInform Abstract: CLEAVAGE OF PHENETOLE BY HYDROGEN CHLORIDE IN NONAQUEOUS MEDIA IN PRESENCE OF MIXED OXIDE CATALYSTS

Abstract

Cleavage of phenetole has been studied in presence of HCl and the mixed-oxide cat­ alysts and the catalyst alone without HC!. Cleavage takes place in case of Alz03-ZrOz, Ah03-Mo03, Alz0 3-SiOz, SiOz-ZrOz and SiOz- TiOz catalysts in the presence of HCl in non­ aqueous media. In addition to cleavage, rearrangement also takes place in all the above cases giving 0-, p-ethylphenols along with phenol in the reaction mixture. This has been confirmed by IR studies, gas chromatography and chemical analysis of the reaction prod­ uct. Since the above mixed-oxide catalysts have dual sites (acidic and basic sites) on the surface, reactions were also carried out with phenetole solutions in benzene and n-hexane in the presence of these catalysts without HC!. It was observed that only rearrangement took place giving only 0-, p-ethylphenols and no phenol was formed in all cases. This clearly proves that the catalyst is responsible for rearrangement. The cleavage is brought about by the HCl adsorbed on the catalyst surface. Taking advantage of the existence of the dual sites (acidic and basic sites) present on the surface of catalysts, a mechanism for the reaction has been proposed. The agreement between the acidity and basicity values calculated from our cleavage results and those from measured values supports the mechanism proposed by us, i. e., basic sites (in the presence of HC1) are responsible for the cleavage of phenetole and acid cen­ tres are responsible for re-arrangement of phenetole and this holds good in general for aromatic ethers.