Instrumental Analytical Chemistry
Lab 1: FT-NMR
INTRODUCTION
The NMR is an instrumental that is mainly used to find the structure of organic compounds. The
instrumental is a very precise instrument that can distinguish between different function groups
relative to other structures within the same structure. The use of an applied magnetic field helps
analyze and determine the chemical makeup of a structure. In this experiment we will be analyzing
two different types of spectra; one is for the H1NMR and C13NMR. We will analyze the spectra
compounds of three acids that make up the structural framework of peanut, vegetable, and olive oil.
Then we will analyze the three oils (vegetable, olive, and peanut) to determine which fatty acid is the
major constituent of each. Afterwards we will analyze an unknown mixture of oil and determine what
the ratio of the mixture is and what oil makeup that mixture.
Palmitic Acid
Stearic Acid
Oleaic Acid
PURPOSE
The purpose of this experiment is to learn how to operate and run samples the NMR instrument and use
the NMR to evaluate and analyze an unknown sample.
PROCEDURE
1. Read an overview of the NMR manually, briefly read threw the directions to become familiar
with the instrument.
Prepared NMR sample
2. Added 5-8 drops of sample into a test tube.
3. Added 1mL of CDCL3. Mixed the substances together.
4. Transferred the sample from the test tube into an NMR sample tube. Measured the height and
made sure it was 4-4.5cm.
Running Samples
5. **Ran standards of the three fatty acid oil. The standards were (pamitic, oleic, and steric acid).
For this analysis a H1NMR and C13NMR were ran and instead of running a C 13NMR a C13NMR APT
was ran.
6. Ran H1NMR and C13NMR-APT for peanut oil and vegetable oil.
7. Ran a H1NMR and C13NMR-APT of the unknown A.
** When preparing for the lab, the fatty oils weren’t available for analysis. So step 5 is a step that
wasn’t done but should be in all labs and should be used to help identify the known oils.
DATA
Since the C12NMR-APT spectra didn’t come out that well. We, as a group, decided to base our results
and decision of the H1NMR.
Peanut Oil H1NMR Spectrum
NMR Spectra Peanut Oil
PEAK (1)
NO PEAK 2
Vegetable Oil H1NMR Spectrum
NMR Spectra Vegetable Oil
PEAK (1)
PEAK (2)
Unknown A H1NMR Spectra
NMR Spectra Unknown A
PEAK (1)
Peak 2
RESULTS
The NMR Spectra for between Peanut oil and Vegetable oil there was only minor difference
between the two spectra. I found that the peanut oil and the vegetable oil contained a peak around
1.5 ppm, (PEAK 1) was slightly different from both spectra. The second peak was only visible in the
Vegetable oil (PEAK 2). This peak was only present in the vegetable oil spectrum but not the peanut
oil. Thus, this peak showed to exhibit a different structure.
In the unknown NMR Spectrum, showed both peaks. The peanut oil and vegetable oil peak (PEAK1)
were present. The presence was both at slightly different location around 1.5 ppm. However, an
additional peak was visible on the spectrum (PEAK 2). This peak was the only component found in the
vegetable spectrum. This peak was not present in the peanut oil spectra.
CONCLUSION
Considering that the unknown NMR spectra showed to have a more vegetable oil peaks present
than the peanut oil peaks and the intensity of the peaks were prominent than the peanut oil peak
and/or the peaks from both the peanut oil and vegetable oil spectra respectively, I concluded that the
ratio of oil in the unknown was 70% vegetable and 30% peanut oil.
Due to time constraints I was unable to run a 2D NMR spectrum. Perhaps, if I was able to run an
NMR spectrum for 2D analysis I would have been able to possibly indentify the ratio better. Also, the
sample that needed to be ran were saved until the proceeding lab day, and when we observed our NMR
tubes, the chloroform was lower than 4-4.5cm, which meant that it could have evaporated. This could
have messed with our data a little bit. To fix this problem we just added some more chloroform to the
NMR tube because we assumed that the oil wouldn’t’ have evaporated or degraded. However, we were
uncertain about that we just made an educated guess.
Another problem we faced when using the NMR was that when we were shimming, our line was
a little thicker than normal. This could have been an indication that the instrument had a harder time
locking and finding our sample than it would have been with a fresh made sample.
Another issue we encounter was that the fatty acid weren’t available for analysis. Although I
included that step in my procedure that was just a step added for students to know if my lab was
reviewed for reference. Since the fatty acid weren’t available we didn’t run an NMR on them. Thus, if
we had taken an NMR of the fatty acid we could have possibly gathered more information from the
spectra which could have helped us to indentify the ration of oils in the unknown. I initially have a
thought to look up NMR spectra for the fatty acid but since it made have been with a different NMR
instrument it could have skewed our data analysis.
Overall, using the data we obtained, we found that the ratio of oil within the vegetable oil was
70% vegetable oil and 30% peanut oil.