Issue 10, 2017

A unified view to Brønsted acidity scales: do we need solvated protons?

Abstract

The most comprehensive solvent acidity scale spanning 28 orders of magnitude of acidity was measured in the low-polarity solvent 1,2-dichloroethane (DCE). Its experimental core is linked to the unified acidity scale (pHabs) in an unprecedented and generalized approach only based on experimental values. This enables future measurements of acid strengths and acidity adjustments in low polarity solvents. The scale was cross-validated computationally. The purely experimental and computational data agree very well. The DCE scale includes 87 buffer systems with Image ID:c7sc01424d-t1.gif values between −13.0 and +15.4, i.e. similar to water at hypothetical and extreme pH values of −13.0 to +15.4. Unusually, such high acidities in DCE are not realized via solvated protons, but rather through strongly acidic molecules able to directly donate their proton, even to weak bases dissolved in the solution. Thus, in all examined cases, not a single solvated proton is present in one liter of DCE.

Graphical abstract: A unified view to Brønsted acidity scales: do we need solvated protons?

Supplementary files

Article information

Article type
Edge Article
Submitted
30 Mar 2017
Accepted
03 Aug 2017
First published
07 Aug 2017
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY license

Chem. Sci., 2017,8, 6964-6973

A unified view to Brønsted acidity scales: do we need solvated protons?

E. Paenurk, K. Kaupmees, D. Himmel, A. Kütt, I. Kaljurand, I. A. Koppel, I. Krossing and I. Leito, Chem. Sci., 2017, 8, 6964 DOI: 10.1039/C7SC01424D

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

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