Exposing the Origins of Irreproducibility in Fluorine NMR Spectroscopy.

Exposing the Origins of Irreproducibility in Fluorine NMR Spectroscopy.
Angew Chem Int Ed Engl. 2018 Apr 16;:
Authors: Togni A, Rosenau CP, Jelier BJ, Gossert AD
Abstract
Fluorine chemistry has taken a pivotal role in chemical reaction discovery, drug development, and chemical biology. NMR spectroscopy, arguably the most important technique for characterization of fluorinated compounds, is rife with highly inconsistent referencing of fluorine NMR chemical shifts, producing deviations larger than 1 ppm. Herein, we provide unprecedented evidence that both spectrometer design and the current unified scale system underpinning the calibration of heteronuclear NMR spectra has unintentionally led to widespread variation in the standardization of 19F NMR spectral data. We demonstrate that internal referencing provides the most robust, practical and reproducible method whereby chemical shifts can be consistently measured and verified between institutions to less than 30 ppb deviation. Finally, we provide a comprehensive table of appropriately calibrated chemical shifts of reference compounds which will serve to calibrate 19F spectra correctly.
PMID: 29663671 [PubMed - as supplied by publisher]

Source: Angewandte Chemie - April 16, 2018 Category: Chemistry Authors: Togni A, Rosenau CP, Jelier BJ, Gossert AD Tags: Angew Chem Int Ed Engl Source Type: research