Accelerated hydrazone formation in charged microdroplets

Abstract

Reaction acceleration in droplets is attributed to solvent evaporation leading to increased surface to volume ratios. An acceleration factor of 10(4) , measured relative to the bulk reaction at short times, is readily achieved by simply increasing the droplet distance of flight showing that the same ionization source can be used to monitor reactions with or without acceleration. Copyright © 2016 John Wiley & Sons, Ltd.

“On‐Droplet” Chemistry: The Cycloaddition of Diethyl Azodicarboxylate and Quadricyclane

“…[1] Thes eminal discovery by Breslow and co-workers [2] of the rate acceleration of Diels-Alder cycloadditions in water suggested that the poor solubility of hydrophobic reagents may promote, rather than hamper, certain classes of reactions.I ndeed, the exploration of reactions at the organic-aqueous interface has become at opic of research in the synthetic community. [4a] Work from our group, [10] as well as others, [11] has demonstrated that reactions in microdroplets generated through electrospray ionization (ESI) are often orders of magnitude faster than their counterparts in bulk solution. Termed "on-water" chemistry by Sharpless and coworkers, [4] these reactions now encompass adiverse range of transformations including cycloadditions, [5] sigmatropic rearrangements, [6] aldol reactions, [7] and Grignard additions.…”

“…Termed "on-water" chemistry by Sharpless and coworkers, [4] these reactions now encompass adiverse range of transformations including cycloadditions, [5] sigmatropic rearrangements, [6] aldol reactions, [7] and Grignard additions. [4a] Work from our group, [10] as well as others, [11] has demonstrated that reactions in microdroplets generated through electrospray ionization (ESI) are often orders of magnitude faster than their counterparts in bulk solution. [9] Water is an ideal solvent in terms of safety and cost.…”

“…[8] In almost all cases,anacceleration of several to several hundredfold has been noted relative to reactions conducted in organic solvents or even under neat conditions.M ellouli et al examined "on-water" cycloaddition reactions in biphasic microfluidic systems and investigated the role of surface-tovolume ratios on conversion rates,d emonstrating that acceleration can be ascribed to the increased rate of conversion at the surface. [4a] Work from our group, [10] as well as others, [11] has demonstrated that reactions in microdroplets generated through electrospray ionization (ESI) are often orders of magnitude faster than their counterparts in bulk solution. Additionally,m any reactions conducted "on-water" allow for the facile isolation of products,w hich often precipitate and can be collected by simple filtration rather than after an often complex and time-consuming workup.…”

Microsecond and nanosecond polyproline II helix formation in aqueous nanodrops measured by mass spectrometry

“…Bimolecular reactions can occur up to 10,000 times faster owing to these factors. 37,38 The unimolecular process of folding measured here should not be affected by concentration changes due to solvent evaporation at the low concentrations used (Supplementary Information), but interactions with the surface of the nanodrops may have an effect on folding rates compared to those in bulk solution.…”

Accelerated Chemical Reactions and Organic Synthesis in Leidenfrost Droplets

“…[17] TheLeidenfrost version of this reaction also showed asubstantial acceleration This reaction is known to be accelerated in the charged droplets generated by nESI when the distance between the spray source and the MS inlet is increased.…”