Fourier Transform Nuclear Magnetic Resonance (FT-NMR)
Introduction:
Fourier transform nuclear magnetic resonance (FT-NMR) spectroscopy is based on the
measurement of absorption of electromagnetic radiation in the radio-frequency region. It is used in
determining the structure of organic compounds. A sample is placed in a strong magnetic field so the
nuclei can develop the energy states required for absorption to occur. The most common nuclei are
hydrogen and carbon.
Purpose:
The purpose of this lab is to become comfortable using the NMR instrument. A Proton, C13, and
2D analysis will be run on a sample.
Procedure:
1.
2.
3.
4.
Pick unknown A or B
Prepare an NMR sample in an NMR tube
Run a Proton and C13 analysis
Run a 2D analysis
SOP:
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 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.
Data:
See spectrum attached in notebook on pages 108-117.
Conclusion:
This week we ran several samples through the NMR. Those samples were vegetable oil, olive
oil, peanut oil, and Unknown A. On the first day, we were only able to collect Proton and C13 spectrum
for peanut oil and Proton spectrum for vegetable oil. This was due to error on our part. We set the
carbon spectrum to run for an hour, which took up most of lab time and did not allow us to collect any
other C13 spectra. On the second day, we fixed this error and used the Carbon Apt so that each carbon
sample only ran for about 16 minutes. Thus, we were able to collect Proton and C13 spectrum for
vegetable oil, olive oil, and Unknown A. We were also able to run a 2D scan on the unknown. This
unknown corrected well with vegetable oil. All of the peaks matched, therefore, Unknown A is
vegetable oil. Overall, the NMR is an excellent instrument to use to identify organic compounds using
Proton and C13 spectrum.