Quantify the acidity of fluorinated reaction media to promote new reactions

Quantify the acidity of fluorinated reaction media to promote new reactions
Quantify the acidity of fluorinated reaction media to promote new reactions

Present in many pharmaceutical and agrochemical products, fluorine occupies a special place in organic synthesis. Among these products, polyfluorinated compounds (PFAS), harmful, toxic and persistent substances in the environment, are in the process of being banned in the European Union. No wonder the chemical industry is actively seeking effective, simple and non-polluting alternative methods to prepare new biodegradable fluorinated compounds to replace PFAS.

The vast majority of these fluorinated derivatives are prepared from a single Source of fluorine, hydrogen fluoride (HF), an inexpensive primary Source of fluorine. By varying the acidity of the reaction medium by adding organic bases, the reactivity of HF is modified and the syntheses are thus directed towards the desired fluorinated derivative or towards new compounds. To consider new selective and efficient fluorination reactions leading to more virtuous fluorinated compounds, it is therefore essential to start by controlling the acidity of the HF/base media. But surprisingly, no measurement protocol has been reported to evaluate these acidic properties.

Scientists from the Poitiers Institute of Chemistry of Environments and Materials (CNRS/University of Poitiers) propose using nuclear magnetic resonance (NMR) spectroscopy of the fluorine isotope 19F which makes it possible to precisely quantify the acidity of these HF/base media. This method is based on the synthesis and use of specific organic probes whose acid-base properties determined upstream by DFT calculations serve as a reference.

This method, first successfully tested on commercial HF/base reagents, was then applied to a set of common HF/base reagents whose acidities were still unknown. These measurements should provide a better understanding of the crucial role of acidity on the efficiency and selectivity of reactions under these conditions. A study, published in the Journal of the American Chemical Society which could be extended to other acidic reaction media of interest.

Editor: CCdM

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