Deuterium, chemical symbol D or 2H, is an isotope of the element hydrogen which has a nucleus containing one proton and one neutron. A compound containing deuterium is said to be deuterated. Deuterated chemicals are widely used in NMR spectroscopy, either as chemical shift references, as solvents, or to reduce the relaxation rates of NMR signals in large compounds like proteins. Deuterium is a stable, naturally occurring isotope of hydrogen and represents 0.015% of naturally occurring hydrogen, with H-1 representing the remaining 99.985%.
Use in NMR spectroscopy
NMR spectroscopy, which primarily detects the signals of proton atoms, frequently uses a deuterated solvent and/or a deuterated compound as a chemical shift reference. Deuterium atoms also have different relaxation properties so that their use in NMR spectroscopy of large biopolymers such as proteins leads to enhanced signal detection.
Deuterated NMR solvents
Deuterated chemicals that are often used for NMR spectroscopy include:
- d6-acetone (1,1,1,3,3,3-hexadeuteroacetone)
- d3-chloroform (1,1,1-trideutero-chloroform, trideuterochloromethane)
- d6-benzene (1,2,3,4,5,6-hexdeuterobenzene)
Each of these chemicals has a small proportion of undeuterated content, which gives a residual signal that can be used as a (non-zero) reference chemical shift. However, several chemical compounds are specifically used as true reference points.
Chemical shift references
Three deuterated chemicals are widely used reference points for 1H NMR data. In organic solvents, deutero- trimethylsilane (d9-TMS) is used. For aqueous solutions, deuterated DSS or TSP are used instead.