Efficient pKa Determination in a Nonaqueous Solvent Using Chemical Shift Imaging.

Schenck, George, Baj, Krzysztof, Iggo, Jonathan A and Wallace, Matthew ORCID: 0000-0002-5751-1827 (2022) Efficient pKa Determination in a Nonaqueous Solvent Using Chemical Shift Imaging. Analytical chemistry.

There is a more recent version of this item available.

Text
ID ac-2022-002009 revised Schenck et al Efficient pKa_clean 3.pdf - Author Accepted Manuscript
Download (402kB) | Preview

Abstract

pKa is an important property of a molecule which impacts many fields, such as drug design, catalysis, reactivity, and environmental toxicity. It is often necessary to measure pKa in nonaqueous media due to the poor solubility of an analyte in water, for example, many compounds of pharmaceutical interest. Although NMR methods to measure pKa in water are well established, determining pKa in organic solvents is laborious and problematic. We present an efficient one-shot method to determine the pKa of an analyte in an organic solvent in a single measurement. Diffusion of an acid into a basic solution of the analyte and a set of pH indicators establishes a pH gradient in the NMR tube. The chemical shift of a pH sensitive resonance of the analyte and the pH of the solution are then determined simultaneously as a function of position along the pH gradient by recording a chemical shift image of the NMR tube. The pKa of the analyte is then determined using the Henderson-Hasselbalch equation. The method can be implemented in any laboratory with a gradient equipped NMR high-field spectrometer and is demonstrated for a range of pharmaceutical compounds and inorganic phosphazene bases.

Item Type:	Article
Divisions:	Faculty of Science and Engineering > School of Physical Sciences
Depositing User:	Symplectic Admin
Date Deposited:	13 May 2022 14:18
Last Modified:	18 Jan 2023 21:03
DOI:	10.1021/acs.analchem.2c00200
URI:	https://livrepository.liverpool.ac.uk/id/eprint/3154734