Theoretical study of HNCO formation from atomic nitrogen and carbon monoxide in the presence of water

The formation of HNCO has been studied through DFT calculations in comparison with experimental IR measurements. Four different pathways starting from atomic nitrogen, water and carbon monoxide molecules were considered. Among them, the direct formation of NCO in the presence of water corresponds to the most favourable with a relative energy of 11.8 kcal/mol. IR frequencies were found to be in a good agreement with experimental measurements in presence of additional water molecules. Accordingly the most stable reaction path was studied by including an additional water molecule. The results show that the maximum relative energy is lowered to 5.5 kcal/mol owing to the stabilization through H-bonds with water molecules. As such the presence of water seems mandatory to lower maximum energy states and favours the reaction to occur at low temperatures in astrophysical environments.