Structures and properties of unsaturated carbenoid H_2C=CLiF have been determined by using DFT at B3LYP/6-311G~* level. H_2C=CLiF has two equilibrium structures, but only one can exist, the structure is as following: The transition-state of intra-molecular H-transfer reaction of the above structure has been determined, and the average lifes of H_2C=CLiF at different temperatures have been obtained to be τ = 7.9 days at 200 K and τ = 2.4 s at 300 K.

Key words: CARBENE, HYDROGEN TRANSFER, TRANSITION STATE, LIFE