Droplet-based reactions have imparted fundamental and applied research in chemistry. Recently, the use of charged droplets derived from electrospray ionization to increase the rates of solution-phase organic reactions has been explored. We have shown that a new contained-electrospray source enables the use of the droplet environment for quantitative mass spectrometry, excited-state chemistry and electro-catalysis. This presentation will focus on mechanistic insights of this phenomenon, and its application to top-down proteomics [1] and general chemical synthesis. For example, we discovered a new chemical transformation involving the conversion of tetrahydroquinolines into quinolines with Ru(bpy)3Cl26H2O [2]. The mechanism was identified to involve the production of superoxide anions, allowing direct hydrogen atom abstraction. Similar conversion was achieved with DC discharge [3]. Like all other aerobic oxidative reactions, our initial experiments with tetrahydroisoquinoline substrates culminated in the exclusive formation of the imine products. Through detailed DFT calculations, we identified this bottleneck to be due to hyper-conjugation, released both by pi and sigma donation. We will show that reactions studied in the charged micro-droplet environment are directly transferrable to solution-phase conditions.

Accelerated droplet chemistry: How and why?

256th National Meeting (2018)

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