The induction of chemical reactivity through mechanical action has emerged as a green approach to synthesize, transform, and functionalize reactants and materials. This is of particular interest when referring to reactions typically achieved at higher temperatures such as aziridination reactions. A combined experimental and computational investigation is undertaken to analyze the aziridination reaction mechanism of graphene by perfluorophenylazide (PFPA). As a preliminary study, this work computationally examines the aziridination reactions of small (poly)arenes benzene (C6H6) and naphthalene (C10H8) with the concerted addition of methyl azide (N3CH3) using density functional theory (DFT). Naphthalene is also studied under a strained conformation to computationally echo the use of mechanical force. These polyarenes structurally resemble graphene and give insight into the aziridination mechanism of conjugated carbon frameworks. Geometry optimized energy profiles are generated for the different reaction pathways, followed by transition state and vibrational frequency calculations to evaluate the differences in reaction mechanisms and energy barriers. The DFT calculations indicate that the greater the number of aromatic rings in a polyarene structure (i.e., benzene in comparison to naphthalene), the more easily the polyarene reacts and proceeds in an aziridination reaction, due to increased electron delocalization. In addition, calculations also demonstrate that when naphthalene is constrained to a curved conformation, the aziridination reaction barrier lowers by 0.79eV and the reaction pathway accesses a new mechanism, when compared to the respective relaxed reaction. This work suggests that perturbations of the polyarene structure result in significant and favorable changes in reactivity, mapped reaction pathways and energy barriers.

Mechanistic study of polyarenes via aziridination reaction

ACS Spring 2022

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