The Hydration of Aliphatic Aldehydes and Pyruvic Acid in Mixed Solvents

In water/dioxane mixtures and aqueous electrolyte solutions the hydration reaction has been studied. The formation of the gem‐diol of aliphatic aldehydes is associated with the binding of 3 water molecules to the carbonyl group, whereas for pyruvic acid 6 or 7 water molecules are involved in this reaction. Rate and equilibrium constants of the reactions have been determined. The hydration equilibria may be used to measure conveniently the local water activity in the aqueous and non‐aqueous regions of micellar solutions and microemulsions. The reaction rate indicates the local proton activity in these systems.