Acid−Base Catalyzed Reactions in Ionic Water Clusters

Fourier Transform-Ion Cyclotron Resonance (FT-ICR) mass spectrometric studies of both cationic water clusters H + (H 2 O) n, n = 1−70, and anionic water clusters X - (H 2 O) n, n = 1−30, X = OH, O, with acetone and acetaldehyde are reported. For the cations a sequence of ligand exchange and fragmentation reactions results in “solvated proton” complex ion final products. In the anionic OH - (H 2 O) n clusters, on the other hand, an OH - catalyzed aldol addition of the carbonyl compounds with a true covalent bond formation is observed. The anionic and cationic water clusters thus behave similar to basic and acidic aqueous solutions.