Fig 6 . Energetic of the reaction between CI and HNO3 in water cluster.
The different sets of products can be formed for the reaction between CI and HNO3. The formation of P1 is exergonic while the formation of P2 is endergonic. The attainment of these two products is sourced from same intermediate INT which is at the -47.0 kcal/mol in the energy profile diagram. ThisINT is attained via a transition state (TS1 ) with a barrier of 11.42 kcal/mol. The INT then forms two products (P1and P2 ) via two transition states (TS2 andTS3 ). TS3 lies very high in energy and thus the formation of P2 is less likely. Third product P3 is obtained by proton abstraction of CI from nitric acid via a transition state TS4 . The energy barrier for the formation of P3is only 6.96 kcal/mol and the formation of P3 is slightly endergonic (1.99 kcal/mol). From the energy barrier values, it is evident that proton abstraction from nitric acid will be easiest having highest rate constant values which is in agreement with previous theoretical calculations in gaseous phase.13
The calculate rate constant for the product P1 formation is 3.4 X 10-10 cm3molecule‑1 s-1 and the overall rate constant value kTotal is 6.5 X 10-10cm3 molecule‑1 s-1which slightly higher than the gas phase reaction (kTotal = 5.4 X 10-10cm3 molecule‑1s-1).17 The calculated B. R. suggests that the formation of product P1 contributes 52% of the overall reaction channel. This suggests that other reaction channels (Fig 6) has also significant contribution towards product distribution.