Two publications from this lab, in 2011 and 2012, used mass spectrometry to show that the rates of reactions in microdroplets can be accelerated by many orders of magnitude. These experiments used ordinary organic solvents and demonstrated that acceleration occurs at the solution/air interface. An earlier ‘on water’ report of 2005 dealt with organic/aqueous bulk interfaces. Later, we showed that microdroplet acceleration depends on traces of water in the organic solvents but by then the subject had expanded rapidly and, mostly through the efforts of the Zare group, was firmly oriented towards accelerated reactions in aqueous microdroplets.
This presentation covers three matters. (i) The mechanism of acceleration to which we contributed a simple insight regarding partial solvation at the interface, viz. that solvation is more important in the reagents than in the transition state in bimolecular reactions, thus increasing rate constants. (ii) The application of reaction acceleration in synthesis, both for scale-up (g/h) and in conjunction with small-scale high-throughput reactions (1 Hz) in a drug discovery platform (Figure) capable of the rapid screening, collection, and bioactivity testing of nanogram amounts of drug analogs. (iii) The implications of accelerated microdroplet reactions in prebiotic chemistry and origin of homochiral life.

<b>Reagents are converted during droplet flight into products that are collected in the corresponding array format before bioassay. Both steps use DESI-MS</b>

Reagents are converted during droplet flight into products that are collected in the corresponding array format before bioassay. Both steps use DESI-MS

Dylan T. Holden

Graduate Research Assistant, Purdue University Department of Chemistry

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