A DFT study on reaction force approach of ammonia catalysed amide bond formation reaction between ammonia and formic...

A reaction force approach of ammonia catalysed stepwise amide bond formation between ammonia and formic acid is investigated using B3LYP/6-31G (d,p) level of density functional theory in gas phase. The stepwise amide bond formation mechanism involves two transition states, namely, TS1, in initial stage and TS2, in final stage of reaction pathway. The potential energy surfaces obtained from IRC calculations on transition state geometries are subjected to reaction force and reaction work calculations. The estimated reaction works of structural and electronic activities in the progress of reaction reflect the unfavorable formation of diol intermediate and preferential formation of formamide. While 91% of the activation energy comes from structural changes in preparative region of TS1 path, the structural and electronic rearrangements respectively, share 57.6% and 42.4% of total activation energy of TS2 pathway. The atomic resolution of IRC pathways and natural charge analysis reveal the importance of hydrogen atom of catalyst in TS1 path and the oxygen of water molecule in TS2 path in the progress of reaction.