Solvent-independent determination of heteroatom protonation states from NMR spectra by differential deuterium isotope shifts.

The NMR-spectroscopy based structure elucidation of organic molecules containing heteroatoms is often obstructed by the difficulties in determining the heteroatom protonation states. Here we describe a simple but broadly applicable approach for the determination of the protonation states of heteroatoms. Differential deuterium isotope shifts observed upon the addition of small amounts of H2O or D2O to any solvent can be used to determine the protonation states of heteroatoms.

Extracting unresolved coupling constants from complex multiplets by a real-time J-upscaled SERF experiment.

The measurement of small homonuclear coupling constants is often prevented by either their small size and/or overlap with other signal splittings. Here, we present a real-time method to extract such couplings without interference from other splittings, with a resolution that is beyond conventional NMR spectra. In this real-time J-upscaled SERF experiment, homonuclear coupling is removed by slice-selective pure shift NMR, whereas scalar coupling to only one selected signal is reintroduced by selective refocusing.