The aminopropylated Silica-Gel hydrochloride (APSG. HCl) proved to be an efficient catalyst for the rapid conversion of carbonyl compounds in the corresponding acetals with high yields and in mild and selective conditions. In addition to the obvious advantages offered by heterogeneous catalysis, the present method results very useful when the presence of a weakly-acidic function chemically bonded on the catalyst surface (alkyl ammonium salt). is ...