Reply to the ‘Comment on “The chemical reactions in electrosprays of water do not always correspond to those at the pristine air–water interface”’ by A. J. Colussi and S. Enami, Chem. Sci., 2019, 10, DOI: 10.1039/c9sc00991d

Abstract

We explain why chemical reactions in/on electrosprays of water may not always represent those at the air–water interface. Thus, electrospray-based techniques cannot be relied upon as generalized “surface-specific” platforms for water.

On the formation of hydrogen peroxide in water microdroplets

“…Probing the air-water interface of molecular thickness, however, remains a daunting research area due to the challenges associated with direct experimental interrogation as well as the limitations of the water models 14 . Therefore, investigating the properties of the water surface is a research frontier in chemical science, sometimes invoking vigorous debates [14][15][16][17][18][19][20][21][22][23][24][25][26] . With this preface, we introduce the latest reports on the chemical transformation of water into hydrogen peroxide (H 2 O 2 ).…”

The Air–Water Interface of Water Microdroplets Formed by Ultrasonication or Condensation Does Not Produce H2O2

“…The mechanism suggested for H 2 O 2 production in water microdroplets is based on the presence an an ultrahigh electric field at the air–water interface (∼10 7 V/cm), which drives the formation of •OH radicals from OH – ions; these •OH radicals combine to form H 2 O 2 . , Currently, there is no theoretical explanation available for this intriguing phenomenon. We note that probing the air–water interface of <1 nm dimensions is a daunting task and sometimes fraught with interpretational ambiguities and/or experimental artifacts. − …”

On-Water Selectivity Switch in Microdroplets in the 1,2,3-Triazole Synthesis from Bromoethenesulfonyl Fluoride

“…Mass spectrometry electrospray ionization chambers are designed to generate plumes of microdroplets and are well suited for studying reactions in this environment. C–N bond formation, heterocycle synthesis, cycloadditions, Heck reaction, and even protein digestion have been examined under these conditions. − Development of instrumentation and careful engineering design made it possible to execute reactions at the intersection of two spray cones even in a biphasic manner, which was called “on-droplet” chemistry. − In a recent study Zare and co-workers demonstrated that chemoselective N-alkylation of indoles derived in a three-component Mannich-type reaction was observed in droplets, whereas C-alkylation proceeded in the bulk phase …”