My compounds are aromatic. The peaks and integration of aromatic region is accordingly, still some extra peaks mainly from 0.7 to 3 ppm, are observed. the peaks from 2 to 3 are usually singlet. The compounds are purified by c.c using DCM or ethyl acetate/n-Hexane. Can you please share your experience??????? Thank You.
Please check the following paper; it is available online:
NMR Chemical Shifts of Common Laboratory Solvents as Trace Impurities. J. Org. Chem., 1997, 62 (21), pp 7512–7515
I guess they are related to the residual amounts of the applied solvent(s). For example, the singlet is related to DCM (singlet at 5.3 ppm), acetone (singlet at 2.1-2.2), ethyl acetate (singlet at 2 ppm), n-hexane (0.8-1.3 ppm). Check the accurate place of solvent picks in SDBS...
From my experience, many peaks are coming from solvent traces or other impurities (e.g. grease used with glass material). In the case of solvent traces, I don't think that your peaks are related to ethyl acetate or n-hexane, as you should find multiplets.
Simply, you should do first a blank experiment (solvents without compound) to identify the source of impurities.
Alternatively, I recommend to do additional NMR experiments (1D 13C and/or 2D-HSQC) to assign these peaks and check whether it is related to your compounds.
With additional information, I think that we will be able to solve the problem.
Hope it helps.
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