Abstract: The reaction mechanism of CH3CHF radical reacting with HNCO had been investigated by density functional theory (DFT). The geometries and frequencies of reactants, intermediates, transition states and products had been calculated at the B3LYP/6- 311++G (d, p) level. To obtain more accurate energy result, single point energies were calculated at the QCISD(T)/6- 311++G(d, p) level. The vibration analysis and the IRC analysis approved the authenticity of intermediates and transition states, and the reaction processes were confirmed by the changes of charge density at bond- forming critical points. Seven feasible reaction pathways of this reaction had been found and studied. The results indicated that the pathway which produced the stable molecule fluoroalkyl imide had the lowest activation barrier and it was a competitive pathway that took place easier than the hydrogen transfer process.

Key words: CH3CHF radical, HNCO, Reaction mechanism, Activation barrier