Dear Mohammed,

You state that your compound was "very neat..." I am not sure what you mean by "very neat". Does it mean that no solvent was used for obtaining the spectrum, or only that it was very pure? If there was moisture present, and/or D2O was used as solvent, the water signal / residual HDO signal could be around 4.8 ppm (note, however, that the location of the water signal is very much dependent on the solvent). Methanol OH may be at ca. 4.87 ppm. CD2Cl2 also gives a residual signal at ca. 5.32 ppm. Not knowing anything about your sample, its background, and solvent if any, my suspicion is that the "very tall peak" is likely be from water / HDO. 

For detailed information, you might want to look up on the Internet: (PDF) NMR Chemical Shifts of Common Laboratory Solvents as Trace Impurities by Hugo F. Gottlieb et al., J. Org.Chem. 1997, 62(21) pp. 7512-7515 Table I;  and NMR Solvent Data Chart, Cambridge Isotope Laboratories, Inc.

Good luck in your research!

yes it may be acetone may be in compound or in acetone d-6

Some time the solvent used in the reaction remains with the product and that give tall peak. So i would suggest you to look for the region in NMR spectrum where your solvent peak should come. If it is matching then ok otherwise this could be due to impurity  in your deuterated solvent used for NMR sample preparation.

Dear Mohammed,

You state that your compound was "very neat..." I am not sure what you mean by "very neat". Does it mean that no solvent was used for obtaining the spectrum, or only that it was very pure? If there was moisture present, and/or D2O was used as solvent, the water signal / residual HDO signal could be around 4.8 ppm (note, however, that the location of the water signal is very much dependent on the solvent). Methanol OH may be at ca. 4.87 ppm. CD2Cl2 also gives a residual signal at ca. 5.32 ppm. Not knowing anything about your sample, its background, and solvent if any, my suspicion is that the "very tall peak" is likely be from water / HDO. 

For detailed information, you might want to look up on the Internet: (PDF) NMR Chemical Shifts of Common Laboratory Solvents as Trace Impurities by Hugo F. Gottlieb et al., J. Org.Chem. 1997, 62(21) pp. 7512-7515 Table I;  and NMR Solvent Data Chart, Cambridge Isotope Laboratories, Inc.

Good luck in your research!

Dear Mohammed

I think Anthony answer is very relevant to explain your spectra, most likely your solvent contain  a water residual or you use D2O and the  HDO signal would be around 4.8 ppm

Best

Abdul-Hamid

Dear Mohammed,

as you have been told, for knowing what may be the impurity is necessary to know what solvent you have used. The impurity may be water or remaining solvent from the synthesis. Maybe if you leave drying the compound in a glass desiccator all the weekend and repeat the NMR analysis next Monday, you will have your compound without the impurity peak if it is due to presence of solvent in the sample.

In case it is due to presence of water in the deuterated solvent, you should dry the solvent with molecular sieve and using it in the preparation of the next NMR samples for diminishing this peak (it is always present but you can reduce its size).

Good luck and best wishes!

The (CH2)signal of benzyloxy (-OCH2Ph) group experimentally appear at 5.2ppm, or may be due to a  solvent 

Thank you all for your great help. The solvent I have used was MeOH-d4, and I did suspect it to be water and it does seem so from your answers which I highly appreciate. This tall peak was seen on almost all the spectra of the other compounds, so is it safe to assume it to be water?

Thank You

Dear Mohammed,

I also suspect that your solvent was "soaking wet" with water. To avoid similar situations we do not buy deuterated solvents in larger bottles (except nonpolar ones) but buy ampoules containing just about the volume required to make one NMR sample (ca. 0.7 mL). This is more expensive but mostly worth the trouble.

Best regards.

Dear Mohammed, 

If all your other compounds were examined also in CD3OD solution and their 1H spectra all showed the same strong peak at ca. 4.87 ppm from TMS, it is safe to assume that water in your solvent (or/and in your sample) is the source. CD3OD is, as are most NMR solvents, hygroscopic to some extent; once the bottle of CD3OD is opened, humidity from the air will be absorbed, and over time, the water peak may get to be larger than the residual solvent peak. Check out the following:

2005-3-University of Alberta NMR News 2005-03. This useful reference shows spectra of CDCl3, C6D6, CD2Cl2, D2O, CD3OD, DMSO, Acetone-d6. Like Prof. Ernst, we also avoided buying deuterated solvents in larger bottles. Although more expensive, small sealed ampules containing the amount of solvent enough for just a single sample can save you a fair amount of trouble. To minimize the residual solvent signal, buy the highest grade (e.g. "100% deuterated") solvent you can afford. But remember, even a "dry" solvent will have a residual signal because there is no real 100% deuterated solvent. But using high grade, dry solvents will minimize the residual solvent peak(s) assuming no water in your sample.

Dear Mohammed,

Other more economical alternative is to buy deuterated solvents in large amounts, but transferring 2-3 mL to a small flask a few days before experiment, to dry the solvent in it with molecular sieve (it is also good to store this flask in a glass dessicator). Remember also to change the flask and the sieve from time to time to avoid contaminations.

Best wishes

Show me the compound structure then it could be find easily.

This signal corresponds to the proton of methylene chlrid solvent (CH2Cl2), so try to evaporate well your solvent .

1H and 13C NMR chemical shifts have been compiled for common organic compounds often used as reagents or found as products or contaminants in deuterated organic solvents.

This signal  corresponds to the proton of trace Impurities of D2O.

Dear Mohammed,

As others have stated, the nature of the solvent used is important in determining this peak.

It could be HOD in deuterated water or water (4.79 ppm)/HOD in MeOD (4.87). In deuterated chloroform, dichloromethane appears at 5.3ppm.

As such, it is really important to dry your compound well before obtaining an nmr spectrum.

Solvents such as DCM can sometimes be difficult to remove, so a trick is to dissolve a couple of times with normal chloroform then rotary evaporate to drive off residual DCM (particularly if your compound is an oil). Once dried, your nmr can then be performed in deuterated chloroform, which will have a chloroform peak in it anyway.

The other option, if you are using MeOD, is to use vials rather than a bottle, as these will have negligible amounts of water in there. Unfortunately, as soon as you expose MeOD to the atmosphere (especially in a humid environment), it will begin to absorb atmospheric moisture, so the trick is to get everything ready and dried then quickly add your MeOD from the vial. However, you will always see some water/HOD in the spectrum.

Regards

 you need to provide the solvent in which you have taken H-NMR, and i also want to suggest you the same publication what Anthony Foris suggested you

i personally feel it may come from traces of CH2Cl2 when your sample is in CDCl3

Dear Mohammed,

As pointed out by all the other correspondents, without information which NMR solvent you used to record your 1H NMR spectrum it is difficult to give you an unambiguous answer.

If there are no other "alien" signals in your spectrum, depending on your NMR solvent, the signal could be caused either by water (originating either from your NMR solvent [absolute organic solvents are hygroscopic] or from your sample if it was not dried under vacuum in a desiccator prior to analysis) or by DCM if your sample was e.g. extracted using this solvent.

Water typically gives rise to an 1H NMR signal at 4.8 ppm while DCM will give a signal at 5.3 ppm.

It could be water signal (4.8 ppm)

Until you name the solvent you used for NMR, it is difficult to say what it could be, it could be water or DCM 

Yes, I think this peak belongs to the water signal. However, don't assume anything. Try to dry your compound as much as possible and then try to solve it again in a brand new solvent (avoiding contacting with water and/or humidity). Run the NMR again and see what happens. 

Best, 

Pedro M. 

PS: When I was doing my PhD, I run up to 3 cycles of freeze-dry to my samples in order to avoid 1H signal from water. 

Water. What was the protocol leading up to NMR? Did you use any water?

The two things that first came to my mind were water (or HOD) and dichloromethane.  Neither typically appears at exactly 5.0, but both appear near 5. If you are sure neither of these could be in the sample, consider taking a spectrum of  whatever materials you used in your process.  Perhaps one of them is contaminated.