The Isolation of Trimyristin From Nutmeg
Written by Adi
The purpose of this experiment was to illustrate the process of obtaining a pure organic compound from a natural source. The subfield of organic chemistry that deals with isolating and studying chemicals found in nature is natural products chemistry. Extraction, distillation, recrystallization, and chromatography are used the techniques that are used to isolate and purify chemical compounds from natural sources. The extraction of nutmeg seed to isolate trimyristin was performed in this lab.
Materials: sand bath, nutmeg, filter paper, round bottom flask, funnel, tert-butyl methyl ether, boiling chips, plastic connector, distillation column, ring stand and three-pronged clamp, pipette, centrifuge tube, pressure filtration assembly (a plastic pipette which has had the tip cut off and which has had a small hole cut into the squeeze bulb), 25mL Erlenmeyer flask, acetone, ice bath, vacuum, Hirsch funnel, filter flask, 6 M NaOH, 2 mL of 95% ethanol, concentrated HCl, water, graduated cylinder, weighing scale, Mel-Temp device and capillary tubes
Procedure: I warmed the sand bath first, and then turned it down to about 30°C. I tared a piece of filter paper and weighed 0.999g of ground nutmeg onto it. The nutmeg was then carefully transferred to a round bottomed flask with a funnel. I added 3mL of tert-butyl methyl ether and 3 boiling chips, connected the black distiller connector to the flask, and the distillation column. I clamped this to the ring stand and let it boil for 10 minutes. After allowing the solids to settle, I pipetted the solution into a centrifuge tube. It settled again and I pipetted it into a 25mL Erlenmeyer flask, through a pressure filtration device (plastic pipette with a small hole in the bulb), in order to leave behind as much solid as possible. I put 2 mL of tert-butyl methyl ether into the round bottom flask, heated it again for about five minutes, and repeated the same procedure. I applied a very gentle breeze with air inside the fume hood so that the solution evaporated and left behind crude trimyristin. I let that stand to dry a few minutes, and recrystallized it with acetone. I let it cool in the ice bath for 15 minutes before collecting the crystals via vacuum filtration. The crystals were then air dried and placed on a piece of filter paper. I used 0.624 grams of the crystals for the hydrolysis. The 0.624 grams of trimyristin crystals were added to a round bottom flask with 2mL of 95% ethanol and 1 boiling chip. I secured the flask to the three-pronged clamp on the stand over the sand bath to heat for 45 minutes. While that boiled, I recrystallized the remaining trimyristin, but there wasn’t enough product to utilize for a melting point assessment. After the hydrolysis, I let the solution cool, poured 8mL of distilled water into a 50mL Erlenmeyer and poured the solution into another flask. In the fume hood, I measured 2mL of concentrated HCl drop wise, stirring it with a glass stirring rod. Myristic acid precipitated. I cooled the beaker for 10 minutes in the ice bath, collected the precipitate via vacuum filtration, and left them overnight to dry
In lab data/observations: I had 6.7 grams of crude trimyristin upon weighing it. The crystals came out to be 0.629 grams, and I used 0.624 grams for the hydrolysis. The myristic acid crystals came out to weigh 0.528grams. The precipitation of myristic acid was brown and fumed a bit while I added the concentrated HCl. The evaporation of the tert-butyl ether was an interesting process. The remains were the yellow solid of crude trymyristin mentioned in the lab description. I got almost no crystals in the second recrystallization; they were visible, but not plenty enough to be put into the mel-temp device.
Results:
The percent recovery of crude and once recrystallized trimyristin from nutmeg was (0.629grams/0.999)(100%) = 62.9%
The percent yield of myristic acid obtained in the hydrolysis was as follows:
0.629 grams of trimyristin crystals collected (trimyristin = 723.16g/mol)
0.528 grams of myristic acid crystals collected (myristic acid = 228.37092g/mol)
Theoretical yield: (0.528 grams)(1mol/228.37092g) = 0.00231 moles of myristic acid crystals, (0.00231moles)(723.16g/mol) = 1.6705 grams
% yield = (actual/theoretical)(100%), thus (0.528g/1.6705grams)(100%) = 31.6%
Melting point of once recrystallized trimyristin: 54-55°C
Post-Lab questions
1.) What is the structural difference between saturated, monounsaturated, and polyunsaturated fats? Of which kind is trimyristin?
2.) In the first recrystallization, after the solid has been dissolved in warm acetone, the solution is allowed to cool slowly to room temperature. In an older procedure the warm solution was placed directly into an ice bath. How does this older procedure differ from a normal recrystallization and what might be the consequences?
3.) One triglyceride present in animal fats is tristearin (glycerol trioctadecanoate). What is the theoretical yield, in grams, of stearic acid upon hydrolysis of 1.8 g of tristearin? (See an Organic text, CRC Handbook, or ChemFinder.com for structure and MW.)
4.) In the hydrolysis of trimyristin the reaction mixture is heated at about 75° for 45 minutes. What is the purpose of heating a reaction mixture?
5.) If the mixture were heated at 40° for 45 minutes, what would be the result
1. If the carboxylic acid portion of the fat contains no alkene groups, the fat is said to be saturated. If one alkene group is present the fat is monounsaturated. If more than one alkene is present the fat is polyunsaturated. In a monounsaturated fat, if the alkene is one carbon in from the far end of the long chain (away from the ester group), the fat is said to contain omega-1 (read as omega minus one – omega refers to the end of the chain so omega-1 refers to one carbon in from the end) fatty acids. Trimyristin is a saturated fat.
2. This older procedure differs from a normal recrystallization in that most of the other numerous ether soluble components of nutmeg remain in the acetone solution. They must be allowed to dissolve further before the solution is put into an ice bath.
3. (1.8g)(1mol/891.48grams) = 0.0020 moles tristearin
(0.0020moles)(3) = 0.0060 moles
(0.0060moles)(891.48g/mol) = 5.4 grams
4. The mixture is high-boiling . A reaction mixture is boiled to separate the complex mixture of compounds.
5. If the mixture were heated at 40° for 45 minutes, the complex compounds would separate. Hydrolysis would yield trimyristin.
