FT-NMR Laboratory
Fourier Transform Nuclear Magnetic Resonance
Purpose:
The purpose of this experiment was to gain a greater understanding of nuclear magnetic
resonance through experimentation. This was done through the analysis of two
different oils and two mixtures of the two.
Introduction:
Nuclear Magnetic Resonance, NMR, is used primarily to analyze organic compounds.
The NMR uses an applied magnetic field to spin the molecule, and the electrons oppose
the applied field, which gains a response from the nuclei of the atoms. The spectra
produced from this analysis from the spinning of the molecule are interpreted based on
several aspects, including chemical shift, multiplicity, and splitting. All of these occur
based on the nuclear response to this applied force field. The NMR can produce spectra
from the analysis of the hydrogen atoms on a compound, as well as the carbon atoms.
These spectra are interpreted in order to learn the structure of the compound and the
orientation of the carbon and hydrogen atoms in the molecule.
Method:
For this experiment, we were given two oil samples, peanut and vegetable oil, and two
mixtures to analyze.
We mixed about 4 drops of the oil samples with about 1mL of chloroform-d, mixed the
samples in test tubes, and placed them in NMR tubes at the appropriate volume for
analysis.
We ran each of the four samples for C13APT NMR analysis and H1 Proton NMR analysis.
All spectra are located in supplementary folder.
NMR Standard Operating Procedure:
Preparing the sample:
Deposit your sample (80mg for a solid, about 4 drops for a liquid) in a test tube with 1mL of solvent.
Mix the sample and place in an NMR tube with cap. Your sample should come to about 4cm in the NMR
tube.
Loading the sample:
Wipe your sample tube with a kim wipe so that the tube is clean when you run the sample. Place your
sample tube in the blue spinner carefully. The blue spinner will be in the wooden stand by the
computer, and the tube should be placed in the spinner while it is still in the stand. Make sure that when
you put the sample in, the bottom of the tube touches the stand. This will help get it in at the right
length. Hold the tube from the top so you don’t get fingerprints on the bottom of the tube.
Follow the instructions in the packet by the computer for step by step instructions on running TopSpin.
After you’ve opened the program and ejected the placeholder tube from the NMR, wait until the
placeholder pops out of the NMR and switch it with your sample carefully and quickly. Then you can
inject the sample tube and continue working on your experiment with TopSpin.
Make sure that when you are done and you have ejected your sample that you put the placeholder tube
back into the NMR and you inject it before closing TopSpin.
Conclusion:
In this experiment, we were certainly successful in gaining better understanding of the
FT-NMR. We previously learned a little about the instrument in our Organic Chemistry
courses, and this gave us the chance to learn how to operate the instrument on our
own. We were able to obtain good spectra for each of the samples, however,
interpreting the results appears to be a difficult task. The original procedure was
supposed to involve several different acids that might have helped identify the
components of different oils, but for this we were given two oils and two mixtures of
the same oils, both in 70:30 ratios, just reversed for the other mixture. The spectra we
obtained for both mixtures (Labeled Unknown A and Unknown B) were almost exactly
the same, and we can only conclude that the similarity is due to the fact that the
mixtures were too similar.