Among all carbenes studied so far, 1 CN carbene is found the most effective for N 2 activation which is due to the presence of the C = O group. Thus, a carbene is modeled by adding one more C = O group to 1 CN carbene which is presented in Figure . Nitrogen activation reaction is studied with this carbene. The effect of substitution is also studied. The energy profile diagram for the activation reaction with this carbene (5 R ) is presented in Figure . The reaction between N 2 and carbene 5 R (Figure ) follows similar trends as it is observed for four other carbenes. First, the pre-complex 5A R is formed through an endergonic process. The very next step is the transformation of 5A R to 5B R through a transition state T S5 R . The effect of substitution is almost the same for this carbene too. The activation energy barrier for different substituents obeys the order CN < CF 3 < H < P h < M e < OM e < tBu. The lowest and the highest activation energy barrier for this step is 20.8