Correlation 2D-NMR experiments involving both 13C and 2H isotopes in oriented media: methodological developments and...

Area of Science:

• Nuclear Magnetic Resonance Spectroscopy
• Isotope Chemistry
• Analytical Chemistry

Background:

• Nuclear Magnetic Resonance (NMR) spectroscopy is crucial for molecular structure determination.
• Deuterium (2H) NMR spectra can be complex, especially for polydeuterated or unmodified solutes in oriented solvents.
• Assigning signals in (2)H NMR spectra is challenging due to quadrupolar doublets.

Purpose of the Study:

• To review and highlight the utility of correlation 2D-NMR experiments for assigning (2)H NMR spectra.
• To discuss various pulse sequences, their properties, and applications in isotopic analysis.
• To emphasize the role of these techniques in enantiomeric and enantiotopic analyses.

Main Methods:

• Correlation 2D-NMR experiments, specifically (13)C-(2)H and (2)H-(2)H with (13)C relay.
• Utilizing high-field NMR spectrometers (21.1 T) with cryogenic probes for enhanced sensitivity.
• Application in both specifically and non-selectively deuterated analytes, including unmodified ones.

Main Results:

• (13)C-(2)H correlation experiments effectively assign overcrowded (2)H NMR spectra by correlating to well-dispersed (13)C signals.
• The reviewed pulse sequences demonstrate broad applicability across various isotopic modifications and solvent systems.
• These methods prove instrumental in analyzing chiral systems, facilitating enantiomeric and enantiotopic differentiation.

Conclusions:

• Correlation 2D-NMR experiments are indispensable tools for the assignment of (2)H NMR spectra, especially in complex or overcrowded systems.
• The sensitivity of modern NMR spectrometers enables the analysis of even isotopically unmodified compounds.
• These techniques offer novel and powerful approaches for enantiomeric and enantiotopic analyses in chiral environments.