Why does NMR use deuterated solvents?
There are three reasons why deuterated solvents are used in NMR spectroscopy.
Reason 1: To avoid swamping by the solvent signal.
There is usually much more solvent than sample in an NMR tube.
An ordinary proton-containing solvent would give a huge solvent absorption that would dominate the
But deuteration is never complete, so in
You always get a solvent signal from
Reason 2: To stabilize the magnetic field strength.
The field strength of superconducting magnets tends to drift slowly.
Modern NMR spectrometers measure the deuterium absorption of the solvent and adjust the field strength to keep the resonance frequency (field strength) constant.
Reason 3: To accurately define 0 ppm.
The difference between the deuterium frequency and 0 ppm (TMS) is well known.
Modern spectrometers can "lock" onto the deuterium signal, so the addition of an internal reference like TMS is not usually required.