To explicit the carbene -N 2 reaction, the orbital energies of the frontier molecular orbitals of carbene (1 H ) and N 2 molecule are compared and presented in Figure . In Figure , it is observed that the lowest energy vacant π * orbital of N 2 has positive orbital energy. Thus, the donation of σ electron pair of carbene to this orbital would be difficult. Energies required for different electronic transitions are given in Figure . The minimum energy required for the brown path is 7.87 eV which is significantly higher than the green path.