Objective:
To isolate trimyristin from nutmeg seed by solvent extraction
To purified it by recrystallization.
To obtain an infrared spectrum of the isolated trimyristin from the recrystallized trimyristin from the experiment.
To study the difference between the infrared spectrum results of the isolated trimyristin from experiment 3 and the recrystallized trimyristin
Materials and Methods
Procedure for the isolation trimyristin from nutmeg seed by solvent extraction
15.13g of ground nutmeg seed, 40ml of acetone and five antibumping granules were placed into a 100ml round bottom flask. The ground glass joints of the 100-ml reaction flask and the outer joint of the reflux condenser were lubricated by Vaseline to prevent the glass joints from freezing together. The mixture was then allowed to reflux for 15 minutes.
Then, the heating mantle was switched off and the hot solution was filtered into a 100 ml conical flask containing 15 ml acetone on a hot water bath using a hot stemless funnel which was preheated to about 80。C and fitted with a fluted filter paper. The extracts were allowed to cool in an ice bath until crystallization was complete while the solid material was isolated by suction filtration.
Procedure for recrystallization
The isolated product from ex 3 was placed in a 100ml conical flask. Then 30ml acetone and a very small amount of activated charcoal were added. The mixture was warmed in a hot water bath. After that, the solution was filtered and allowed to cool in an ice bath. The purified trimyristin crystals were collected by suction filtration. The weight and melting point of the product were also determined.
Procedure for infrared spectroscopy
About 15 to 20 mg of the recrystallized sample was ground in an agate mortar, then a drop of the paraffin oil was added, and was ground for 2 to 5 minutes until a mull was formed. The mull was transferred to the bottom salt plate of a demountable cell. The top plate was then placed and twisted to distribute the sample evenly and eliminate all air pockets and the spectrum was run. After running the sample, the salt plates were wiped clean with a tissue paper saturated with acetone.
Results
For experiment 1,
Mass of nutmeg used for solvent extraction: 15.13 g
Mass of trimyristin isolated: 3.046g
Percentage of non-purified trimyristin in nutmeg =20.13%
For experiment 2,
Mass of sample used for purification = 3.00 g
Mass after recrystallization: 1.639 g
Percentage yield of recrystallization = 54.63%
Melting point of Trimyristin after recrystallization:
1st :55.8。C-59.5。C
2nd: 55.8。C-58.2。C average m.p.:55.8。C-58.85。C
Colour of the filtered solid before recrystallization: yellow powder
Colour of the filtered solid after recrystallization: white powder
Discussion
Question
The apparatus for refluxing a solution is always left open to the atmosphere during heating and is never stoppered because if the apparatus is in a closed system and the temperature of that system is increased, air will expand. And the solvent will evaporate into gas so the pressure inside will increase also. As the pressure inside will continue to increase and until the apparatus cannot stand the pressure, the apparatus will break and the solution may spread. That is why it is really unsafe when heating in a closed system.
IR spectrum
In our group, the IR spectrum of recrystallized sample was done. In the spectrum, there were a peak at 1735.84cm-1 which indicated the presence of C=O bond,
peaks at about 1180cm-1 which indicated the presence of C—O bond and the peak at 2842.67cm-1 to 2920cm-1 indicated the presence of aliphatic C—H bond.
By comparing the IR spectrum of un-recrystallized sample from the other group, similar pattern of the spectrum was obtained. Same functional groups were found in that sample but the transmittance of the recrystallized one was much lower than the un-recrystallized one which indicated that the purity of the recrystallized sample was higher.
Source of errors
If the mixture was heating under reflux for too long, other things may also extract. Moreover, there was loss of sample during the transfer process as some solid might adhere on the flasks, Buchner funnel or even the weighting bottle. Some of the trimyristin might not completely dissolve in the hot acetone so less trimyristin was extracted. As the solubility of trimyristin in hot acetone is much bigger than in colder acetone, if we don’t filter quickly after heating, the temperature would decrease and less trimyristin would be isolated. For the IR spectrum of the recrystallized sample, some sharp unnecessary peaks may appear because of the acetone or other impurities as we used acetone to clean the plate which did not evaporate completely before we put them in the spectroscopy.
Improvement
For the purity, we can repeat the process of recrystallization although the yield might be lowered. Moreover, the product could be allowed to dry in the suction filter for more time. Tiny amount of charcoal was added first, then warm the mixture for a while if the yellow colour still present, a little more charcoal is added instead of adding too much at first. For the reflux, it is better not reflux for more than 20 minutes. During reflux, the stand should shake gently so that the trimyristin can better dissolve in the hot acetone and should filter the solution as quick as possible after heating. Finally, wait for a while after cleaning the salts plates or apparatus used for IR spectroscopy so that the acetone can fully evaporate in order not to interfere the results.
Conclusion
There was 1.639g trimyristin with melting point between 55.8.—58.85 ℃ was isolated from natural product.
Reference
Organic Chemistry by Morrison and Boyd (sixth edition)
