Mechanistic investigation of hydrolysis reactions of dithioacetal derivatives grafted on silica gels

Silica gels believed to be grafted with dithioacetal derivatives were recently used for Hg(II) extraction, and were found to selectively remove 94-100% of Hg²⁺ ions from metal ion mixtures. The current studies with one derivative suggest that the functional group in the Hg(II) removal is the mercapto (SH) ligand. The dithioacetal group in (ClCOCH₂S)₂CHPh (2) was hydrolyzed during its reaction with amine (O)₃Si(CH₂)₃NH₂ (3) grafted on silica gel to give the mercapto ligand (O)₃Si(CH₂)₃NHCOCH₂SH (4). The silica gel grafted with the mercapto ligand 4 selectively removed Hg²⁺ ions with reported high capacities.