Post lab 8 - lab 8 PDF

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lab 8...

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Teaching Assistant: Lab Technique: Leave this section blank in your report. But, make sure to tell Gradescope it is on page one of your lab report. Your TA will assign the technique points when they grade the post-lab. Do not delete this text. Purpose: The purpose of this lab is to obtain the pure organic compound Trimyristin from its natural source of nutmeg. This will be done by isolating trimyristin and recrystallizing the product with acetone, then hydrolyzing and acidifying the trimyristin to produce myristic acid. Pre-Lab: Leave this section blank in your post-lab report. But, make sure to tell Gradescope it is on the appropriate page. Your TA should have graded the prelab before you began the experiment. They will assign the awarded points for the prelab with the report. Do not delete this text. In-Lab Observations and Recordings: Enter your in-lab observations here. 

after passing air over yellow aq. Solution it immediately dried up

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became a yellow solid at the bottom of flask

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cream like consistency

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measure Erlenmeyer flask to be 24.033 g

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during part 2 crystals only started forming once flask was put in ice bath

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before ice bath, crude product with heated acetone had to be put back on the aluminum block

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there was too much solvent for the crystals to form

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once crystals formed they were white

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paper weight (what the crystal was on): 0.225g

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looked like they were a small plated structure

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for first recrystallization MP: 54-58 °C

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for second recrystallization MP: 56-58 °C

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final MP: 53-55 °C

Reaction Scheme:

Experimental Procedure: Once the hot plate was turned on (~225 °C), ground nutmeg (1.00 g) was added with tertbutyl methyl ether (3 mL) and 3-4 boiling chips in a round bottomed flask (RBF), and was gently heated for 10 minutes. The boiling mixture was filtered using microfiltration where the 25-mL Erlenmeyer flask was filtered and drained. Tert-butyl methyl ether (2 mL) was added to the liquid and re-filtered using micro-scale filtration to obtain any excess trimyristin. A gentle stream of air is then passed over the solution while warming the flask with a hand until the solvent evaporated. A yellow solid is left over and allowed to air dry after for 5 minutes before obtaining its weight. For every 100 mg of the crude material, about 1 mL of acetone was added to the Erlenmeyer flask and allowed to boil then allowed to cool to room temperature for about 5 minutes. After cooling, the Erlenmeyer flask is placed into an ice bath for another 5-10 minutes

and then placed under vacuum filtration and left to dry. Once dried, the melting point, final weight, and percent yield were recorded. The 5-mL round bottom flask was cleaned and then refluxed using trimyristin (0.060g), 6M NaOH (2 mL), 95% ethanol (2 mL), and 3-4 boiling chips on the hot plate for 45 minutes. During the reflux period, the leftover trimyristin was recrystallized for a second time where it was boiled and then cooled to room temperature for 10 minutes. Once cooled to room temperature, the round bottom flask is placed into an ice bath for 15 minutes and then placed into vacuum filtration. After the reflux period, the contents from the round bottomed flask were obtained and then transferred to a 50 mL beaker containing water (8 mL) and HCl (2 mL) which was added in drops. Once again it was cooled in ice water for 10 minutes and after the period was over, the crystals were collected and filtered. The myristic acid was then left over night to dry and the melting point, final weight, and percent yield were recorded.

Results (modify table as needed). Delete this and the parenthetical text Table 1: Results of Extraction of Trimyristin from Nutmeg Initial nutmeg mass (g) 1.00g

Final crude trimyristin mass (g) 5.103 g

Percent recovery (%)

Observations

(5.103g/1.00)*100 Crude was yellow = and had a cream like consistency 510.3 % Initial mass of nutmeg and the final crude after extraction of trimyristin. The percent recovery and crude product observations were noted.

Table 2: Results of Recrystallization of Trimyristin Initial Trimyristin Mass (g) 5.103 g

Final Trimyristin Mass (g) 0.130 g

Percent Trimyristin MP Recovery (°C) (%) Recrystallizatio (0.13g/5.103g) 54-58 °C n #1 = 2.54% 0.031 g (0.031g/0.07g) 56-58 °C Recrystallizatio 0.070 g n #2 = 44.3% First recrystallization used 13.8 mL of acetone while the second recrystallization used 1.22 mL of acetone. Table 3: Results of Hydrolysis of Trimyristin to Myristic Acid Initial Trimyristin Mass (g)

Final myristic acid mass (g)

Theoretical Yield (%)

Percent Yield (%)

Melting point (°C)

0.069 g

0.053 g

(0.069g / 723.18 g) = 9.54*10-5 moles

(0.065g/0.069g)*10 0 = 94.7%

53-55 °C

(9.54*10-5 moles) (3)(228.38 g/mol) =0.065 g There was a stoichiometric ratio of 3 moles of myristic acid to 1 mole of trimyristin. moles of trimyristin were divided by the molar mass then later multiplied by 3 to find theoretical moles of myristic acid.

Discussion: Trimyristin was extracted from nutmeg seeds and then was used to create myristic acid through hydrolyzing the trimyristin . At the end of this, the target product was found to have a 94.7% yield. Melting point determination was the main method used to identify and test the purity of the product. After the first recrystallization occurred, it was found that the percent recovery was 2.54% and the melting point of the product was around the range of 54-58 °C. The reason for the very low percent recovery of trimyristin could be the fact that some product was lost as air was placed on the product to dissolve in the solvent. Through the given, the melting point of trimyristin is 56-57 °C and the range being much higher and wider in comparison of the

actual range. This means that the compound could have been not completely pure and there were impurities in the product. However, the value of the melting point is very close to the range of the actual melting point of trimyristin. Once the second recrystallization was completed, the percent recovery was found to be 44.3% and the melting point was found to be in the range of 56-58 °C. From the previous recrystallization, the range of the melting point became narrower and closer to the actual value of trimyristin. This demonstrated that the second recrystallization helped in the purification of the product. One possibility that lead to the percent recovery being so low is that the solution was heated too long during reflux heating, and this could have caused trimyristin to evaporate, leading to loss of product. The extraction of Trimyristin from nutmeg led to a percent recovery of 510.3% which shows that errors occurred in the experiment. The 5.103g of crude trimyristin obtained at the start of the experiment could have been a cause from a faulty scale or the weight was not taken correctly. After, the percent yield and melting point of myristic acid was found to be 94.7% and 5355 °C. The actual melting point of myristic acid is 54 °C which demonstrates that the acid was relatively pure with some minor impurity. For the percent yield to be so close to 100%, it means that only a little product was lost and there were basically no errors made in the procedure. The hydrolysis of 1 Mol trimyristin produces 1 Mol glycerol and 3 Mols of sodium myristate. Acidification of the 3 Mols of sodium myristate using HCl (a strong acid) produced myristic acid. In other words, through this experiment a pure organic compound was able to be obtained from a natural source, nutmeg. Because trimyristin is a saturated fat, hydrolysis of this triglyceride followed by acidification yield three molecules of a carboxylic acid, so in this case myristic acid is formed. Overall, the final product was mainly purified with only some imperfections.

Postlab Questions: 1.) What is the structural difference between saturated, monounsaturated, and polyunsaturated fats? Of which kind is trimyristin? Saturated fats have no C-C double bonds and have no alkene groups on their carboxylic portion of the fat. On the contrary, monounsaturated fats have one alkene group present and it is one carbon away from the ester group. They only contain one C-C bond. Polyunsaturated fats contain two or more C-C double bonds. Trimyristin is an example of a saturated fat.

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? The older procedure differs from the current one because sudden cooling can result in more smaller and more temporary crystals as opposed to slow cooling. Slow cooling would cause better purification while fast cooling would cause poor purification. 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.) a. 1.8g tristearin*1 mol/ 891.5 g = 0.002 mol b. 0.02 mol * 3 mol stearic acid= 0.006 mol c. (0.006 mol steric acid * 284.48g)/1 mol= 1.7g stearic acid

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?

Heating a reaction mixture helps catalyze the reaction. hydrolysis wouldn’t occur as quickly if it was just left at room temperature. Boiling helps separate the mixture into desired component.

5.) If the mixture were heated at 40° for 45 minutes, what would be the result? If the mixture was heated at 40° for 45 minutes, the components would still separate. Also, hydrolysis at this temperature would still yield trimyristin due to having a longer time, lower yield, and some contamination....