Covalently linked ethylmercaptophenyl sulfonic acid and ethylmercaptobenzyl sulfonic acid silica materials—Synthesis and catalytic activity

Abstract

New covalently linked sulfonic acid modified silicas have been formed and characterised and their catalytic Brönsted activity evaluated. Thus phenylmercaptoethyltrimethoxysilane, (MeO) 3SiCH 2CH 2SC 6H 5 and benzylmercaptoethyltrimethoxysilane, (MeO) 3SiCH 2CH 2SCH 2C 6H 5, were used to prepare the corresponding T-functional silica derivatives silica ∼ CH 2CH 2SC 6H 4-4-SO 3H and silica ∼ CH 2CH 2SCH 2C 6H 4-4-SO 3H by grafting on commercial silica, followed by sulfonation of the aryl group. Solid-state NMR, DTA and surface area characteristics of the materials are reported. The mercaptophenylsulfonic acid materials are thermally robust highly efficient solid catalysts for a range of transformations including, esterification, etherification and carbonyl group protection. An apparent pore size effect on rate of conversion was observed. The mercaptobenzylsulfonic acid materials were comparatively unstable.