There are two reasons for using deuterated solvents in NMR experiments:
a) modern NMR spectrometers measure the deuterium absorption of the solvent to stabilize the magnetic field strength. As the observation frequency is field dependent, the deuterium receiver notices a field fluctuation through a change of the observation frequency ("lock frequrency") and can correct the field strength correspondingly. You call this the field/frequency lock. In principle one could use other nuclei for the lock, as was done earlier (e. g. 19F), but deuterium is the most convenient;
b) as there is always much more solvent than substance of interest in the sample to be investigated, one uses a deuterated solvent instead of the ordinary 1H-containing solvent to avoid the huge solvent absorption that would otherwise spoil the 1H-NMR spectrum.
As above, also many spectrometers use the trace undeuterated solvent as an internal parameter for determining relative chemical shifts so tetramethylsilane doesn't have to added. Most NMR software have an input for the solvent used, if you select the wrong one the error carries over into the analysis and the spectra will be frame shifted by a number of ppm. This can be very annoying when the default solvent is CDCl3 and your compounds are only soluble in D6-DMSO.
Other than what Ludger said above, which I completely agree with, I'd like to point out that many cases you don't need to use deuterated solvents at all! It all depends on the nucleus that you are measuring. For example, unnecessary to lock and sometimes even disturbing to use deuterated solvents with 31P NMR. You can put a closed capillary of the P-standard in your reaction mixture or even better for avoiding potential overlapping with the standard, to measure your capillary standard only once in a deuterated solvent (of your choice) and then save the shim file. After this you, you can record as many unlocked 31P NMR spectra as you wish by reading in the shim file and turning off the lock-power. I used this practice over 20 years without a problem for following various catalytic reaction in their real undeuterated solvents. Of course, you can use the same practice in 2H,19F, 29Si, 195Pt, etc NMR. Even in 1H and 13C NMR you can get useful spectra using undeuterated solvents only, when the investigated region is far from the big solvent peak. For example, you can get nice hydride peaks (appear typically much under 0 ppm) again directly from your investigated reaction mixture. (Need to turn off lock and to use RG=1).
the answers given by the colleagues are correct and valid, I would just add that it is also possible to perform experiments in non-deuterated solvents by applying a sequence of suppression of the solvent. This procedure is often used with the water, due it allows to determine the mobile protons (OH, NH, SH etc...) that in D2O exchange the H with D and are not determinable.
All the above answers are correct. I suggest you look at Thomas Hoye's paper from around 1998 ( University of Minnesota). Hoye also had a short article in Chemical and Engineering News on this topic. You can use a non-deuterated solvent in a number of cases, such as when you need to follow kinetics by NMR and you solvent peak (peaks) are away from an area of interest. Older NMR spectrometers (+15 years) will not have the dynamic range to look at these samples, but using suppression techniques usually makes it possible (Presat, Watergate, Excitation Sculpting, WET (for multiple resonances).
One issue with using non-deuterated solvents is shimming, especially on older spectrometers. On old spectrometers, you have to shim on the FID. This isn't an easy task and is why NMR spectrometer vendors have automated the shimming task. It is the hardest task to explain and do efficiently! There are ways to do these things. IT depends on necessity and diligence.
Right. There are several tricks to get nice and correct unlocked spectra from non-deuterated solvents. One of these that I forgot to mention in my previous answer above, that before measuring a series of unlocked spectra (turning off the lock-power), the spectrometer should be locked (and shimmed) on the same deuterated solvent (can be neat or a sample from the previous measurement) as the one in which the appropriate internal or external standard (and shim file) was once recorded. This is to assure that the chemical shifts are correct (the field is set at the right place). We didn't have any problems using this method even 25 years ago:).
Another answer is use the protonated solvent, but add a capillary of your deuterated solvent. This way you can lock and shim and hopefully get good spectra. You will still need to suppress solvent signals.
Indeed, this is also a good option and for nuclea other than 1H and 13C you don't need solvent suppression. But for high-pressure or high temperature measurement (and may be just for convenience), the former method seems more feasible.
Coming back to the original question, I think we can summarize that you can carry out (a lot of) measurements in a non-deuterated solvent but you still need a deuterated solvent (at least for the setup) for the reasons given above to make it adequately possible.
Elaborating on point (b) of Ludger Ernst’s reply, deuterated solvents are used in proton NMR because the resonance frequency of a deuteron (2H) is very different from that of proton (1H). Therefore, one would not have to worry about peaks from the solvent in the proton NMR spectrum. For example, consider a 400-MHz NMR instrument (field strength, B = 9.4 T). The resonance frequency of a deuteron in this instrument would be equal to (gamma/2pi)*B = 61.4 MHz, which is far off (a chemical shift of –846486 ppm!) from the resonance frequency of the proton (= 400 MHz). The key difference: gamma/2pi = 42.6 MHz/T for proton and 6.5 MHz/T for deuteron. Deuterated solvents are often not 100 % deuterated. Small peaks corresponding to residual protons in the deuterated solvent are, therefore, see in proton NMR spectra.
Thanks all for that
Please, Martha D Morton, I've looked for Thomas Hoye's article, but I couldn't find it
can you help me to get it?
if you try directly with non deuterated solvent, you will see nothing in the spectra, it is as if you write with blue pen in a blue sheet of the same blue color, hope it helps
There are three reasons why deuterated solvents are used in NMR spectroscopy.
Explanation:
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 1H-NMR spectrum.
Most 1H- NMR spectra are therefore recorded in a deuterated solvent, because deuterium atoms absorb at a completely different frequency.
But deuteration is never complete, so in CDCl3, for example, there is always some residual CHCl3.
You always get a solvent signal from CHCl3 at 7.26 ppm.
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
The outer tube should hold the sample you wish to run the T1 and T2 measurements, mainly due to concentration. A 1.7 mm capillary normally holds about 30 uL. This is enough D2O to establish and hold lock, but will increase the amount of time you need to signal average to get reasonable data on your important sample.
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 1H-NMR spectrum.
Most 1H- NMR spectra are therefore recorded in a deuterated solvent, because deuterium atoms absorb at a completely different frequency.
But deuteration is never complete, so in CDCl3, for example, there is always some residual CHCl3.
You always get a solvent signal from CHCl3 at 7.26 ppm.
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
it is necessary to used deuterated solvents for NMR experiments otherwise signal from solvent may mix with PMR/CMR signals from compounds leading to miss interpretation.
it is necessary to used deuterated solvents for NMR experiments otherwise signal from solvent may mix with other signals from compounds leading to miss interpretation.
It's is because if we don't use deuterated NMR solvent then will get a single peak of protons of that solvent, since it's present in excess than the compound. For example in case of DMSO when it absorbs moisture than we get a big and broad peak of H2O and other important peaks get faded up.
As I wrote earlier it is plainly not necessary to use a deuterated solvent for eventually recording very nice unlocked 1H, 13C, 31P etc. solution NMR spectra on modern high-frequency spectrometers. Shimming of these samples is also not a problem. However if you are a beginner to NMR spectroscopy, I suggest you should start with solutions in deuterated solvents until you learn how to carry out reliable unlocked NMR measurements from protonated solvents.
It is essential that deuterated solvents are used in NMR, to ensure that only the signals of the hydrogens in the sample are obtained.
There are ways with nearly every NMR software I have used to attenuate the solvent signal, you just need to know the ppm value or frequency value of the peak, depending on your instrument. Locking without deuterium is the major issue with running non-deuterated solvents. There are ways around this that have been discussed by earlier commenters, and I have used similar processes in the past. It is possible to run without a deuterated solvent, but it is not worth the effort in most cases.
It is necessary to use deteriorated solvents for NMR experiments as deuterium is non-magnetic nuclei which will not give rise to NMR signals. If solvent contains proton the mixing of the signal due to sample with that of solvent will occur.
It is necessary to use deteriorated solvents for NMR experiments as deuterium is non-magnetic nuclei which will not give rise to NMR signals. If solvent contains proton, the mixing of the signal due to sample with that of solvent will occur.
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