A $^{19}$F Solvatomagnetic Comparison Method for the Determination of the α1 Scale of Solvent Hydrogen‐Bond Donation and Its Application to Deep Eutectic Solvents
Abstract
We develop a nonsolvatochromic comparison method for the determination of the α1 scale of solvent hydrogen-bond acidity by means of $^{19}$F NMR spectrometry. We compare the $^{19}$F chemical shifts of 4-fluoro-2-methylpyridine (as a sensitive hydrogen-bond acceptor probe) and of 4-fluoronitrobenzene (as a chemically similar but less basic reference probe). This so-called 19F solvatomagnetic comparison method yields the hydrogen-bonding contribution to δ ($^{19}$F)(4-fluoro-2-methylpyridine) that is well correlated to 1 values obtained from the solvatochromism of Reichardt's betaine dye. Therefore, this solvatomagnetic comparison method is applied to determine the α1 values of 13 choline chloride–based deep eutectic solvents.
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