Structure Determination of Vegetable Oil to Biodiesel (acid and base catalyzed)
ID: 1015343 • Letter: S
Question
Structure Determination of Vegetable Oil to Biodiesel (acid and base catalyzed)
I need help labeling these three NMR spectra. One is of vegetable oil, the other two are the acid and base catalyzed results of the vegetable oil to yield Biodiesel. I'm looking to label the major differences amongst the three (the diagnostic signal) as well as the major constituent of the Biodiesel in the acid and base catalyzed results.
I should clarify that the three H-NMR images were given to me with no additional information. It was told that not every single peak needs to be labeled but rather the major differences amongst the three should be noted to show what the transesterification process does. The major constituent, I'm assuming, for the acid-catalyzed version would be propyl ester? And for the base-catalyzed version ethyl ester? Please comment if you need additional information.
Vegetable Oil H-NMR
From right (the "ppm" side) to left (down to #9) are the integration numbers if they are too hard too see from the picture:
9.08---51.98---6.56---10.22---6.20---4.11---2.00---1.96---10.20
Vegetable Oil Acid Catalyzed + 1-propanol H-NMR (to yield Biodiesel)
From right (the "ppm" side) to left (down to #9) are the integration numbers if they are too hard to see from the picture:
7.65---18.48---5.12---3.61---0.70---2.20---2.15---2.00---3.29
Vegetable Oil Base Catalyzed + ethanol H-NMR (to yield Biodiesel)
From right (the "ppm" side) to left (down to #9) are the integration numbers if they are too hard to see from the picture:
4.78---29.92---3.50---5.25---3.17---3.52---2.00---1.02---1.02---5.17
Explanation / Answer
Let's consider the NMR spectras as a) vegetable oil b) acid catalyzed +propanol c)base catalyzed +ethanol
In b) the triplet signal of a) (as visible from the image) at 4.1 and 4.3 is clearly absent during the transesterification reaction.
The signal at 4.1 and 4.3 arises from R2C=CH2 group unsaturation present in the vegetable oil(probably oleic acid) at a). The signal disappears during acid catalysed reaction but is present during base catalysed reaction in c).
Again in c) a new singlet appears at 4.5. due to the proton group of RCO2CH-