Condensation reactions assisted by acidic hydrogen bonded hydroxyl groups in solid tin(ii)hydroxychloride

Abstract

Tin(II)hydroxychloride is reported as a heterogeneous Brønsted acid catalyst. Sn(OH)Cl was synthesized by a precipitation method and characterized by XRD, FT-IR, ¹H MAS NMR, SEM, TG-DTA and N₂ sorption. The acidity measurements of tin(II)hydroxychloride by FT-IR pyridine adsorption and ¹H MAS NMR showed the presence of Brønsted acidity. The Brønsted acidity can be attributed to strong hydrogen bonding between the –OH and Cl groups. Sn(OH)Cl showed high activity for important condensation reactions such as the Prins condensation, Claisen–Schmidt condensation and ketalization. The catalytic activity of Sn(OH)Cl was compared with that of SnO, SnO₂ and Sn₂(OH)₂O. The catalyst was recycled three times with a negligible decrease in activity.