DFT study of the nucleophilic addition of water to ketenes

The geometries of the different stationary points of reactants, products, and transition states of the nucleophilic addition of water to cyanoketene and methylcarboxyketene have been identified by optimizing every degree of freedom by density functional theory at the B3LYP/6-31++G** level of theory. The computational results for methylcarboxyketene in both the gas and solvated phase agree with the explanation based on experimental data, according to which the nucleophilic addition of water or alcohols to ketenes obtained from malonates (in our case represented by methylcarboxyketene) occurs by a concerted pseudopericyclic mechanism. The results of the calculations also agree with the experimental data for addition to cyanoketene. This reaction occurs through a zwitterionic intermediate, but in contrast to the previous reaction the solvent is essential for the process to occur. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007).