The hydration of aliphatic aldehydes in aqueous micellar solutions

Abstract

The acid-catalysed hydration of a series of aliphatic aldehydes from propanal to decanal has been studied in the presence of sodium dodecyl-sulphate (SDS) and dodecyltrimethylammonium chloride (DTAC) micelles. The hydration equilibrium is reduced when the aldehyde is bound to the micellar surface owing to a decrease of the water activity in the surface region to a_W,s= 0.83. The hydration rate is increased by the presence of SDS micelles and decreased by the presence of DTAC micelles. The change in reaction rate is quantitatively explained by the partition of aldehydes and protons between the bulk aqueous region and the surface region. The partition coefficients are determined.