Determination of the Hammett Acidity of HF/Base Reagents

Mélissa Longuet (1, 2) , Kassandra Vitse (1, 2) , Agnès Martin-Mingot (1, 2) , Bastien Michelet (1, 2) , Frédéric Guégan (1, 2) , Sébastien Thibaudeau (1, 2)

1 IC2MP [Poitiers] - Institut de chimie des milieux et matériaux de Poitiers [UMR 7285]
2 Université de Poitiers - Faculté de Sciences fondamentales et appliquées

Harnessing the acidity of HF/base reagents is of paramount importance to improve the efficiency and selectivity of fluorination reactions. Yet, no general method has been reported to evaluate their acidic properties and experimental designs are still relying on trial-and-error approach. We report a new method based on ¹⁹F NMR spectroscopy which allows highly sensitive measures and short-time analyses. Advantageously, the basic properties of the indicators can be determined upstream by DFT calculations affording a simple yet robust semi-empirical approach. In particular, the indicators used in this study were rationally-designed to fit on the conceptually-appealing and commonly-used Hammett scale. This method has been applied to commercially-available and recently developed HF/base reagents.

Mots clés: Acidity scale; Hydrogen fluoride; Fluorinating agent; Nmr Spectroscopy; Dft calculation

Domaines: Chimie

Mélissa Longuet, Kassandra Vitse, Agnès Martin-Mingot, Bastien Michelet, Frédéric Guégan, et al.. Determination of the Hammett Acidity of HF/Base Reagents. Journal of the American Chemical Society, 2024, ⟨10.1021/jacs.4c02344⟩. ⟨hal-04552304⟩