Ab initio studies on topological analysis and substituent effects of reactions between ketenimine and olefin

The cycloaddition reactions between ketenimine and olefin have been studied theoretically. For the model reaction (H2C=C=NH + H2C=CH2), the stationary points are located by HF/6-31G, MP2/6-31G* and B3LYP/6-31+ +G**. The topological analysis shows that both transition states are open-ring structures, i.e. only one bond to be formed has bond critical point. For the reaction of H2C=C=NH with (CF2)(3)C=CF2, the activation barriers for different approaching modes have been lowered. While for the reaction of (CF3)(2)C=C=NH with (CF3)(2)C=CF2 ,the reaction across the C=N double bond in ketenimine becomes more feasible than that across the C=C one. (C) 2000 Elsevier Science B.V. All rights reserved.