Acid-catalysed solvolysis of 1,1-diphenylethyl methyl ether in highly aqueous media. Reaction via ion–molecule pairs?

Abstract

The acid-catalysed solvolysis of 1,1-diphenyl-1-methoxyethane (1-OMe) to 1,1-diphenylethanol (2) and 1,1-diphenylethene (3) has been studied in aqueous solvents. Iodide ion accelerates the solvolysis. The twofold increase in rate observed in 20 vol% DMSO in water in the presence of 0.8 mol dm^–3 I^– instead of Cl^– may be explained by nucleophilic attack on a carbocation intermediate of ion–molecule type that undergoes significant internal return, or by a specific salt effect. The addition of water to the carbocation, generated by solvolysis of the p-nitrobenzoate 1-PNB, is catalysed to a small extent by general bases. The acid-catalysed hydrolysis of 1-OMe is accelerated slightly by formic acid buffer.