Volume 56, Issue 4 e4585
SPECIAL ISSUE - RESEARCH ARTICLE

Reaction acceleration at air-solution interfaces: Anisotropic rate constants for Katritzky transamination

Yangjie Li

Yangjie Li

Department of Chemistry, Purdue University, West Lafayette, Indiana, USA

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Tsdale F. Mehari

Tsdale F. Mehari

Department of Chemistry, Purdue University, West Lafayette, Indiana, USA

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Zhenwei Wei

Zhenwei Wei

Department of Chemistry, Purdue University, West Lafayette, Indiana, USA

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Yong Liu

Yong Liu

Department of Analytical Sciences, MRL, Merck & Co., Inc., Rahway, New Jersey, USA

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R. Graham Cooks

Corresponding Author

R. Graham Cooks

Department of Chemistry, Purdue University, West Lafayette, Indiana, USA

Correspondence

R. Graham Cooks, Department of Chemistry, Purdue University, West Lafayette, IN 47907, USA.

Email: [email protected]

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First published: 09 June 2020
Citations: 25

Yangjie Li and Tsdale F. Mehari contributed equally to this work.

Abstract

To disentangle the factors controlling the rates of accelerated reactions in droplets, we used mass spectrometry to study the Katritzky transamination in levitated Leidenfrost droplets of different yet constant volumes over a range of concentrations while holding concentration constant by adding back the evaporated solvent. The set of concentration and droplet volume data indicates that the reaction rate in the surface region is much higher than that in the interior. These same effects of concentration and volume were also seen in bulk solutions. Three pyrylium reagents with different surface activity showed differences in transamination reactivity. The conclusion is drawn that reactions with surface-active reactants are subject to greater acceleration, as seen particularly at lower concentrations in systems of higher surface-to-volume ratios. These results highlight the key role that air-solution interfaces play in Katritzky reaction acceleration. They are also consistent with the view that reaction-increased rate constant is at least in part due to limited solvation of reagents at the interface.