Caffiene Extraction Lab PDF

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Experiment 5: Extraction of the Natural Product Caffeine John Doe– A00xxxxxx CHEM - 2423-OO1 – Organic Chemistry I, Summer 2021 Dr. Khalid Salmani 21 July 2021

Experiment 5: Extraction of the Natural Product Caffeine I.

Introduction Caffeine is one of the of the most commonly used central nervous stimulants in the world. It is commonly consumed in the form of beverages, such as coffee or soda, or in pill form to prevent drowsiness. It is a naturally occurring organic compound that is produced by many plants such as the Cocoa plant found in South America. The purpose of this lab is to extract caffeine from tea bags using dichloromethane (DCM). This lab reinforced the principles of miscibility and immiscibility and gave students hand-on practice with organic extraction technique. Students were able to determine the purity of the extracted sample by comparing its melting point to the known melting point of caffeine found in literature.

Caffeine Molecule

II.

Pre-Lab Questions 1. What are the 2 types of liquid-liquid extraction? A. A: The two types of liquid-liquid extraction are extraction with an immiscible organic solvent and acid/base extraction. 2. Define the term miscible and immiscible. A. A: A miscible substance is one that is able to be mixed and form a homogenous solution. An immiscible substance is not able to be mixed, thus a heterogenous solution is formed. 3. What 2 characteristics are needed between the 2 solvents used for the caffeine extraction process for the liquid-liquid extraction to succeed? A. A: Both compounds should be miscible with the first solvent whereas the second solvent should only be miscible with one of the constituent compounds in the initial mixture. It is also important that both solvents are immiscible with each other so that separate layers are formed in the separation funnel. 4. What component of the caffeine structure allows it to be classified as an alkaloid? A. A: Caffeine is considered an alkaloid because it is a naturally occurring organic compound that contains primarily N atoms. 5. What bond vibrations and stretching frequencies should you observe in the IR spectrum of caffeine? (See Results) 6. A 12 fl. Oz. can of coke has 46 mg of caffeine. If you extracted caffeine from 125 mL of coke, how much caffeine, in grams, would you expect to collect? A. 125 mL 1 fl oz

46 mg

29.5 mL 12 fl oz

= 16.24 mg of extracted caffeine

III.

Procedure First, 6 tea bags, each of which contained a theoretical caffeine content of 40 mg, were placed into a 500 mL Erlenmeyer flask. Next, 12 g of calcium carbonate and 125 mL of water were added to the flask. The solution was then brought to a boil using the hot plate. Once the solution reached a boil, the flask was removed from the hot plate for a few seconds, then placed back on the hot plate and was allowed to reach boil again. The hot plate was then turned off and the solution was allowed to cool to room temperature. Using the vacuum filtration apparatus, the solution was slowly filtered. The cooled, filtered solution was then placed into a 500 ml separation funnel. The first 15 mL portion of dichloromethane was then added to the solution in the funnel. The rubber stopper was then placed in the opening of the funnel and the pressure was released. The funnel was then rocked very gently about 12 times. It was very important to avoid vigorous rocking in order to prevent the formation of an emulsion. The funnel was then placed on a ring clamp, the rubber stopper was removed from the mouth, and the solution was allowed to separate into 2 layers. The bottom layer of the solution was then drained into a separate 250 mL flask. A second 15 mL portion of DCM was then added to the funnel. The process was then repeated. The rubber stopper was then placed in the opening of the funnel and the pressure was released. The funnel was then rocked very gently about 12 times. The funnel was then placed on a ring clamp, the rubber stopper was removed from the mouth, and the solution was allowed to separate into 2 layers. The bottom layer was once again drained into the 250 mL flask. Finally, the third 15 mL portion DCM was added and the process of rocking, layer separation, and removal of the bottom layer was repeated a 3rd time, exactly the same way as the first two times. The 250 mL flask then contained approximately 45 mL of solution composed of the 3 separate extractions of the bottom layers from the separatory funnel. Next, 3g of anhydrous magnesium sulfate was added to the solution for the purpose of drying it. The dried solution was then added to a clean, dry 100 mL round bottom flask and the solvent was evaporated on a rotary evaporator. A thin layer of white, crystallized caffeine remained in the flask. The flask was then weighed in order to determine the amount of crude caffeine that was obtained. The caffeine was then transferred from the flask to a wash glass using a small amount of acetone. The crystals were allowed to air dry. After the sample was dried, the experimental melting point of caffeine was determined and an IR spectrum was obtained.

IV.

Table of Chemicals Chemical

Quantity

Calcium carbonate3

12 g

MW, g/mol 100.09

Dichloromethane4 Acetone1 Water2 Caffeine5

45 mL 20 mL 200 mL (see data)

84.93 58.8 18.015 194.19

Decomposes at 899 40 56 100 Sublimes at 178

Magnesium Sulfate6

3g

120.37

N/A

BP, C

MP, C 825

Density, g/cm3 2.93

-96 -95 0 236

1.33 0.791 0.9998 1.23

1124

2.66

V.

VI.

Observations

Data

Theoretical Yield of Caffeine per Tea Bag

40 mg/bag

Total Theoretical Caffeine Yield (6 bags)

240 mg

Recovered Caffeine

65 mg

Percent Recovery

27.08%

Experimental MP of Caffeine

227C

Actual MP of Caffeine

236C

Percent Error

3.81%

VII.

Results Extraction (Dichloromethane) yielded 65 mg of caffeine as a white crystal (27.08% recovery). Melting point was measure as 227C (3.81% error; lit mp 236C).

Figure 1.1: IR Spectrum of Caffeine

Image taken from SDBS database

IR Analysis: Caffeine’s structure contains a total of 4 double bonds, all of which can be seen in the 15001800 cm-1 region. First, highlighted in blue are the two C=O bonds which are located around 1650-1750 cm-1. Out of the 3 different types of double bonds, these are the most intense due to the substantial difference in electronegativity between carbon and oxygen. To the right of that, there is a very small peak highlighted in pink. This is the C=C located around 1600-1700 cm-1. This double bond has the weakest intensity because it is between atoms of the same electronegativity. Finally, highlighted in green is the C=N which is located around 1600-1650 cm-1. This peak is of intermediate intensity; the difference in electronegativity is greater than C=C, but not as great as C=O. Finally, there are 2 small peaks in the 2700 – 4000 cm-1 region which is the region of hydrogen bonding. Note that one of the peaks is slightly below 3000 cm-1 and the other is slightly above 3000 cm-1. HC sp3 bonds are always found in the 2850-3000 cm-1 and H-C sp2 bonds are located from 3000-3100 cm-1, so we can assume that the leftmost peak is the hydrogen bonded with the sp2 hybridized carbon and the peak to the right of that is the hydrogen bonded to the sp3 hybridized carbon.

VIII.

Discussion and Conclusion The purpose of the lab was to perform a successful extraction of the organic molecule caffeine from tea leaves. Each tea bag theoretically contained 40 mg of caffeine, so the total theoretical amount of caffeine was 240 mg. After performing the extraction, we were left with 65 mg of recovered caffeine in the form of white crystals. This is equivalent to only a 27.08% percent recovery; only a little over a quarter of the theoretical total amount of caffeine in the tea bags was recovered at the end of the experiment. However, even though this was a relatively low percent recovery, the purity of the extracted caffeine was high. The experimental melting point of caffeine, 227C, differed from the actual melting point of caffeine found in literature, 236C, by only 9C. This equates to only a 3.81% error, suggesting that the extracted caffeine was very pure. There are several things that could have been sources of error in this experiment. Firstly, students were instructed to rock the funnel very gently. If students rocked the funnel too vigorously, it could cause the formation of an emulsion which was undesirable. Another source of error could have occurred when the tea extract was transferred from the flask though the filter and into the funnel. When pouring the extract from the flask into the filter, it is important to press the tea bags so that all absorbed water/ tea extract ended up in the funnel. If the tea bags were not pressed well, some of the caffeine could have been lost in the tea extract that was absorbed by the tea bags, leading to a decrease in % recovery. There was a lot of transferring of substances between different glassware in general, and each transfer presented the opportunity for losing some of the caffeine. Finally, another issue that may have skewed the percent recovery calculation is the theoretical amount of caffeine in each tea bag. Theoretically, each bag of tea should contain 40 mg of caffeine. However, this is merely an approximation, as it is extremely unlikely that each bag contained exactly 40.0 mg of caffeine. For example, if each tea bag actually contained exactly 37.0 mg of caffeine instead of the theoretical 40 mg, our percent recovery would hav e rose to about 29% instead of 27%. Although this certainly had some effect on our calculation, it was not a major contributor to our low percent recovery of caffeine. The most significant contributor to our low percent recovery was most likely the loss of caffeine during transfer between glassware, as mentioned previously.

IX.

Post-Lab Questions 1. Caffeine is classified as a teratogen. Define that term. A. A: A teratogen is something that causes the malformation of an embryo during pregnancy. They should be avoided by the mother during pregnancy at all costs. 2. In this experiment we use 2-propanol as our organic solvent for extraction. If we chose to use dichloromethane for our extraction, which layer would be the organic layer? Why? A. A: Between water (density: 0.9998 g/cm3) and dichloromethane (density: 1.33 g/cm3), DCM is the denser of the two. Therefor DCM would be the organic bottom layer with the water layer separated above it.

3. Ethanol is miscible in water. Can it be used to extract the caffeine? Why or why not? A. A: You would not be able to use ethanol because ethanol and water are miscible with each other; they would mix and form a homogenous solution instead of separating into 2 distinct layers. X.

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