Recent studies have demonstrated that chemical reactions that are considered unlikely to happen in bulk water can occur spontaneously in microdroplets. This phenomenon raises fundamental questions: to what extent can this reactivity be enhanced, and how much energy can microdroplets impart to the reactants? To address this, we used high-resolution mass spectrometry to investigate the direct C-N bond cleavage of benzylamines in aqueous microdroplets. Our results reveal that ions formed in microdroplets possess exceptionally high internal energy, which facilitates facile C-N bond cleavage. Using the survival yield method, a mean internal energy of 93 kJ/mol for these reactive ions is determined. Further analysis highlighted key interfacial effects responsible for this reactivity. The superacidic interface promotes precursor protonation, making the heterolytic cleavage of the C-N bond favorable. Moreover, based on DFT calculations, it is proposed that the interfacial electric field induces C-N bond cleavage in protonated benzylamines. These findings deepen our understanding of the capability of microdroplets to make "impossible" reactions possible from an energy scale.
Zhou et al. (Fri,) studied this question.