FESTA: An Efficient Nuclear Magnetic Resonance Approach for the Structural Analysis of Mixtures Containing Fluorinated Species

Abstract

In complex mixtures, proton nuclear magnetic resonance (NMR) spectra are often very crowded, making spectral analysis complicated or even impossible, particularly when detailed structural information about the mixture components is needed. A new 1D NMR method (fluorine-edited selective TOCSY acquisition, FESTA) is introduced that facilitates the structural analysis of mixtures of species that contain fluorine. It allows simplified H spectra to be obtained that show only those protons that are in a spin system coupled to fluorine of interest. The new method is illustrated by factorizing a complexH spectrum into subspectra for individual spin systems involving different F sites.

Improving the Sensitivity of FESTA Methods for the Analysis of Fluorinated Mixtures

“…A good starting point is to acquire 1 H and 19 F 1D NMR spectra, with and without decoupling. In complex mixtures with a lot of overlapping signals it may be difficult to extract the required information, in which case it is helpful to run the 19 F-selective reverse INEPT element alone (that is, the first part of the SRI experiment), 32 in order to determine which protons are coupled to the selected 19 F. Another option is to run a pure shift experiment, such as PSYCHE, 40,41 to determine heteronuclear coupling constants without interference from homonuclear couplings.…”

“…The synthesis and application of fluorine-containing compounds continue to increase in popularity, notably due to the use of such compounds as pharmaceuticals − and agrochemicals. , For structure elucidation, heteronuclear multidimensional NMR experiments using 1 H– 19 F correlations are available (e.g., hetero-COSY, − HETCOR, − HOESY, − and heteronuclear TOCSY), but these are time-consuming if high resolution is required in the indirect dimension. As an efficient alternative, the selective 1D FESTA (fluorine-edited selective TOCSY acquisition) methodology exploits the high spectral resolution of 19 F NMR to obtain clean 1 H NMR subspectra for individual spin systems involving different 19 F sites. Selecting different 19 F resonances allows independent examination of the individual proton spin systems of a complex mixture.…”

DREAMTIME NMR Spectroscopy: Targeted Multi‐Compound Selection with Improved Detection Limits

“…[4] However, the limitation of such traditional approaches is that they struggle to isolate compounds in complex mixtures due to signal overlap. DREAMTIME is novel in that it combines doubly selective excitation, [5][6][7][8][9] with multiple amplitude-and phase-modulated waveforms, [10] allowing many molecules to be co-selected. By passing the magnetization through a phase-cycled double quantum filter, only the J-coupled magnetization is refocused while all other unwanted signals cancel.…”

New 19F NMR methodology reveals structures of molecules in complex mixtures of fluorinated compounds

“…31 In the case of uorinated organic compounds, 19 F atoms provide a 100% NMR active tags already present in molecules, enabling 19 F-centred NMR structure determination. An example of this approach includes the FESTA family of NMR experiments [32][33][34] that provide 1 H- 19 F chemical shi correlation and 1 H- 19 F coupling constants. The FESTA experiments require selective manipulation of individual 1 H and 19 F resonances, which is neither achievable (in particular for 1 H resonances) nor practical for very complex mixtures, such as investigated here.…”