Naomi Bryner
NMR lab
Week of 3/11/13
Introduction:
Nuclear magnetic resonance (NMR) spectroscopy exploits an individual atom’s response to a
specific resonance frequency. This allows for observations of magnetic properties demonstrated by the
isotopes of each atom. Atoms within a compound are distinguished via NMR frequency. The frequency
corresponds to the nuclear shielding experienced by each atom’s nucleus. Shielding is determined by
the effects of the electron shells with respect to all the other atoms of the compound.
NMR produces spectra which require interpretation based on the shielding effects each atom
experiences. Relative spectra can be produced by hand using the predicted frequency of a particular
atom (alkane, alkene, benzene, etc.) in combination with the shifts predicted by all other atoms. These
frequencies and shifts are approximate, but are often extremely accurate. NMR is most frequently used
to identify compounds via carbon atoms or protons.
Purpose:
Proton and carbon spectra will be obtained for 3 known oil samples and 1 unknown oil sample.
A 2-D spectrum will be produced to enhance the understanding of the capabilities of the NMR.
Procedure:
1. NMR tube preparation: Place sample (80 mg solid or 4 drops liquid) into test tube and dissolve in
1 mL solvent. Transfer to NMR tube (should be about 4 cm) and seal with a cap.
2. Be sure that the NMR tube is clean (use a KimWipe). Place in the blue spinner while the spinner
is in the wooden stand. For proper placement, ensure that the tube touches the bottom of the
stand.
3. Follow the instruction booklet for instructions on how to eject the placeholder and inject the
tube containing the sample.
4. Continue following instruction booklet to obtain the following
a. Proton spectra (standards and unknown)
b. Carbon APT spectra (standards and unknown)
c. 2-D spectrum (one standard)
5. Be sure to eject sample and replace with placeholder before leaving
Data:
Peanut oil spectra can be found on page 24
Vegetable oil spectra can be found on page 25
Virgin olive oil spectra can be found on page 26
Unknown B spectra can be found on page 27
Conclusion:
Unknown B is suspected to be primarily composed of virgin olive oil. It is possible that a small
amount of vegetable oil was also a component of Unknown B. Peanut oil did not appear to be present in
Unknown B. However, the spectra obtained for peanut oil did not show signals downfield from atoms
about the carboxylic acid tail. It is likely that the peanut oil sample was old and the carboxy group was
degraded. The unknown sample appears to be virgin olive oil, possibly mixed with vegetable oil. It was
difficult to distinguish is peanut oil was present because the standard was missing notable peak,
indicative of sample degradation.