The reaction mechanism of H₂CCF radical with HNCO has been investigated by B3LYP method with 6-311＋＋G(d,p) basis set. The geometries and harmonic frequencies of reactants, intermediates, transition states and products have been calculated at the B3LYP/6-311＋＋G(d,p) level. To get more precise energy information, the energies of stationary points along the pathways were also calculated at QCISD(T)/6-311＋＋G(d,p) level. Intermediates and transition states were confirmed by the results of vibration analysis and the IRC calculation. At the same time, the results of charge density at some bonding critical points confirmed the processes of the reaction. Six feasible reaction pathways were investigated in this study. Analysis indicated that the reaction H₂CCF＋HNCO→IM3→TS5→H₂CCFH＋NCO was the main pathway, the activation energy of which was the lowest. In this pathway, there were a hydrogen-bond complex IM3 and a characteristic hydrogen shift.

Key words: H₂CCF radical, isocyanic acid, reaction mechanism, activation energy