How to Acquire a Good 1H NMR Spectrum

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1.    Choose an NMR solvent appropriate to your compound.

Tips ( see all )

•  Chloroform is the standard solvent to try first. Be aware that it can be acidic; it is a good idea to add potassium carbonate to a bottle when you first open it. Put enough in that it forms a thin white layer at the bottom of the bottle.

•  If your compound is not soluble in chloroform, try benzene (nonpolar or average polarity compounds), acetone (dissolves almost anything) or methanol (polar compounds).

2.    Find a clean, dry NMR tube.

Rule of Thumb ( see all )

•  After washing NMR tubes with acetone, put them in the oven for two hours before using them again.   Acetone hangs around longer than you might think.

3.     Prepare your sample.

a.       Make sure your sample is free of solvent- if your compound is not volatile, placing the flask on a high vacuum line for 5-30 minutes is a good idea.  

b.       Measure the correct amount of sample.  

Rules of Thumb ( see all )

•  For a solid, thinly coat the bottom of a 1 dram vial.

•  For an oil, dip a glass pipette into the oil until you have a column 1/2 inch high.

c.         Dissolve the sample in 0.75 mL of the NMR solvent.

d.         Put the sample into the tube. If any solid remains, filter the solvent into the NMR tube through a pipette with a cotton plug.

4.     Acquire your spectrum.

5.     Process the data, collecting

      a.       Accurate chemical shifts.

      b.       Integration

for all important peaks. This may require you to expand the spectrum, if peaks are close together.

6.    Print the entire spectrum, not just the region with peaks. Then print expansions of regions of interest.

Rule of Thumb ( see all )

•  Print the region from 10 ppm to 0.5 ppm for every spectrum you take.

  1. Draw the expected structure on the spectrum, and label it with your notebook page number.
  2. Number the hydrogens on your drawing and assign them (with labels) to the peaks in the spectrum.