A reaction force perspective of a model amide bond formation reaction

Publication date: Available online 7 February 2019Source: Computational and Theoretical ChemistryAuthor(s): V. Suresh Kumar Neelamraju, Tanashree JaganadeAbstractA reaction force approach of amide bond formation between ammonia and formic acid is demonstrated along with each atom’s contribution to structural changes and electronic reordering of the chemical reaction. The B3LYP/6-31G(d,p) level of density functional theory based calculations were carried out to explore transition states (TSs) of stepwise and concerted amide bond formation reaction pathways. Various stages that characterize structural and electronic properties in the progress of reaction are identified from reaction force calculations on energetics of geometries obtained from intrinsic reaction coordinate (IRC) pathways. The reaction works in preparative region of the pathway are less than that in relaxation stage, reflecting favorable formation of product geometries (Formamide and water). More than 80% of the activation energy comes from structural changes in preparative region. A comparison of reaction force profiles and reaction works in preparative region of TS1 and TS2 of stepwise path and TS3 of concerted path discloses that both the stepwise and concerted mechanisms are equally competent in terms of kinetic feasibility. The atomic resolution of pathways unveils that, hydrogen and oxygen forming the water molecule contribute significantly to the negative reaction energy of product geometries. The prefer...

Source: Computational and Theoretical Chemistry - February 8, 2019 Category: Chemistry Source Type: research