Microdroplet chemistry has intrigued chemist because of the reaction acceleration in small volume droplet, its application in organic synthesis, and the similar conditions in the spatially limited volumes in living organisms. Many of reaction has been reported to speed up 1~6 order of magnitude in the microdroplet then in bulk solution by electrospray (ESI)-based ionization methods, which can generate microdroplet and study the reaction by coupling with mass spectrometry (MS). However, the reaction acceleration phenomena of organometallic catalyzed reaction has not been well studied. We used a palladium complex (Pd complexed with bpnp, Pd3) catalyzed reaction of triple bond reduction to demonstrate the acceleration of organometallic reactions in microdroplet. We found that the Palladium catalyzed reaction in microdroplet accelerated more than 3 order by extractive electrospray ionization (EESI). Intriguingly, even without the catalyst, the reduction reaction can occur with only reducing agent and be accelerated in the microdroplet condition. To investigate the factor and the mechanism of reaction acceleration, we adjust parameters, such as voltage, starting materials, gas pressure and the experimental setup to vary the conditions of microdroplet and the distribution of reactant on the surface. Furthermore, we used tandem mass, ion mobility spectrometry, and in-situ Raman spectrometry to confirm the product to be the same as the bulk solution. Besides using ESI-MS to study microdroplet chemistry, we can also probe the triple bond reduction reaction in microdroplet by droplet-based reactor coupling with in-situ Raman spectrometry. Our results show that the triple bond reduction can occur and be accelerated both with and without the catalyst in small droplet, and the acceleration might be related to the confine of reagent and catalyst on the surface of droplet and the orientation of reaction site on the surface.

Studying reductive reaction of triple bond in microdroplet by extractive electrospray ionization mass spectrometry and <i>in-situ</i> Raman spectroscopy

2019 Fall National Meeting

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Studying reductive reaction of triple bond in microdroplet by extractive electrospray ionization mass spectrometry and in-situ Raman spectroscopy