Generation of 3-aminopropanamide and its cluster formation with nucleation precursors- a theoretical exploration

Aminoamides are formed in the atmospheric environments by the auto-oxidation of the parent diamines. In this work, the oxidation chemistry of diamine (1,3-Diaminopropane, Dap) to the amino amide (3- aminopropanamide, 3-APA) and its new particle formation potential with small atmospheric molecules such as NH₃ (A), H₂O (W) and H₂SO₄ (SA) are theoretically investigated using the M062X/6-311++G** theory. The bimolecular rate coefficient of the ·OH initiated H-atom abstraction is computed to be 1.01 × 10^-11 cm³ molecule^-1 s^-1. Further reaction of the peroxy radical intermediate indicates that the pathway involving γ H- shift of the initially formed radical intermediates to be more favourable on kinetic grounds with the effective bimolecular rate coefficient of 3.87 × 10^-14 cm³ molecule^-1s^-1. The thermodynamic barrier associated with the H-shifts involved in this pathway is in the range of 13-20 kcal/mol. The cluster formation of APA with SA is more favourable than the clusters with W and A, wherein the free energy of formation of (APA)(SA) and (APA)(SA)₂ are -11.3 and -22.6 kcal/mol, respectively. However, the feasibility of cluster formation with W and A increases with the altitude and becomes spontaneous in the case of water at an altitude of 12 km. The present work indicates that aminoamides like 3-APA can participate in the initial stages of new particle formation events by forming clusters with SA molecules. The scattering parameters and topological analysis of different (Amide)(SA) clusters indicate more scattering properties for the (APA)(SA) cluster, which has an adverse effect on the atmosphere. Furthermore, topological analysis indicates that H-bond formation is more prominent in the (APA)(SA) cluster.