Fig. 6. Changes of the interatomic distance and relative energy during succinimide formation.

Panels (a), (c) for the waterless, and (b), (d) for the water assisted reactions on the basis of NBO data (for NBO data see Supplementary Figs. 22–26 within Supplementary Information, Supplementary Tables 2–12 within Supplementary Information, and Supplementary Note 1 within Supplementary Data 2, Supplementary Tables 1–18 within Supplementary Data 2). The IRC paths were calculated in vacuum at the B3LYP/6-31+G(d,p) level of theory. The molecular energy reference point is the optimised „open” conformer of asparagine, calculated at the same level of theory. e, f Schematic mechanism of the succinimide formation for the waterless and for the water assisted reactions, respectively.