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Isolation and Purification of Caffeine Samuel Kolawole, Stuart Hinds, Deliris Diaz, Christopher Silva Organic Chemistry II Lab Onyia Ngozi 2/14/17

Objectives:  To acquire caffeine by means of solid-liquid extraction, liquid-liquid extraction, then solid-liquid separation, simple distillation and finally sublimation  To examine the caffeine using thin layer chromatography (TLC)

Abstract Caffeine was extracted from tea by the use of solid-liquid and liquid-liquid extractions. An acid/base liquid-liquid extraction took place in order to force caffeine into the organic layer. A pure product of caffeine was obtained as the final product. Many sources of error may have occurred such as an incorrect calibration of the scales with which the samples were measured and improper setup of the liquid extraction experiment resulting in some loss of the organic solvent. Introduction Tea is one of the most popular beverages containing caffeine. The form of caffeine found in tea is an alkaloid, specifically a methylxanthine that is bitter and white (C 8H10N4O2). Alkaloids are compounds that contain basic nitrogen and can be found in plants. The structure of the caffeine affects its function. The structure for caffeine can be seen below.

The tea leaves that caffeine can be found in also contain tannic acid. This must be removed from the solution to extract the caffeine. To extract the caffeine, several steps are taken. First, a solid liquid extract takes place to get the solid natural product in the liquid solvent. The second step is a liquid/liquid extraction that isolates the desired compounds from the natural product. For this experiment, we used an acid/base liquid/liquid extraction. This results in an organic and aqueous layer. The ideal solvent in the extraction should have a low boiling point, not react with the solute or other solvents, not be toxic or highly flammable, not miscible in water, be inexpensive, and should readily dissolve caffeine at room temperature. This was achieved by using methylene chloride, which has a low boiling point. The aqueous layer went above the organic layer containing the caffeine. Since the organic layer has many impurities, the third step, sublimation, was used to remove them. To remove the water still in the solution, anhydrous sodium sulfate was used. The solution was then decanted into another container and the waste was disposed of. Then, evaporation with boiling chips and an apparatus were used to get rid of the methylene

chloride. Then another apparatus was used for sublimating the waste from the caffeine, leaving us with the pure product. Then we used Thin Layer Chromatography to determine whether out product was indeed caffeine and how pure it was. The percent yield was calculated and errors were accounted for. Materials The following materials were used in the experiment:  14 Tea bags  Sodium carbonate  Methylene chloride  Sodium sulfate  Ethyl acetate  1-liter separatory funnel  Long neck funnel (long stemmed funnel)  Boiling chips Methods There were seven parts to this experiment that ended in the reception of the results discussed further in this paper. Solid-Liquid Extraction The purpose of this step was to extract caffeine from the tea bags into the solution. To achieve this, we opened 14 packs of tea bags and placed them in a 1-liter beaker, to which we added 6.16 grams of sodium carbonate. To that, we added 250 mL of tap water. The sodium carbonate was used to neutralize the tannic acid extracted from the tea, which would otherwise interfere with the sublimation operation later on. We let the water boil on a hot plate for 7 minutes until we saw water vapor and gas bubbles at the interface between the water and the vapor. We stopped the boiling of the water and lets it rest, speeding up the cooling process by adding ice to the solution. The tea bags were then removed from the beaker without breaking them and were discarded. The beaker was then taken off the hot plate for the next part of the experiment Liquid-Liquid Extraction The purpose of this step was to get the caffeine into an organic solvent. This was done by using the 1-liter separatory funnel and positioning it in the hood by placing a ring clamp at 60% of the height above the stopcock. The tea solution created in the previous step was then added to the separatory funnel through a long neck funnel to which ethylene chloride was added. The stopper was then put in place and the separatory funnel was rocked five times gently to prevent the formation of an emulsion. After each rock, the stopper was removed, pressure was released, and venting was allowed. It was then placed back on the ring clamp to rest until a clear separation of two layers was observed. The stopper was then removed to release pressure again and the bottom organic layer was drained into a 125 mL Erlenmeyer flask that was then stoppered with a cork. The top inorganic layer was then drained into the sink as waste. This solution contains methylene chloride, caffeine, and a small amount of water.

Solid-Liquid Extraction The purpose of this step was to remove the water remaining in the organic solution. To achieve this, 2.13 grams of anhydrous sodium sulfate (a drying agent) was added to the flask containing the solution. We then swirled the solution until it was clear. The sodium sulfate absorbed all of the remaining water in the solution. Solid-Liquid Separation The purpose of this step was to remove the sodium sulfate from the solution. This was done by decanting the supernatant solution into a 125 mL round bottom flask through a long stemmed funnel. The remaining solids were then disposed of as waste. Simple Distillation (Evaporation) The purpose of this step was to remove the methylene chloride from the solution. This was done through evaporation. A distillation apparatus was set up in a hood allowing for venting to prevent the buildup of pressure. Three boiling chips were then added to the solution in the round bottom flask to prevent superheating. The heating mantle was placed under the round bottom flask and was turned on while the system was left run by letting cold water run through the apparatus. This was done until no liquid was left in the round bottom flask and all of the methylene chloride had been removed and distilled into the 150 mL beaker placed at the end of the apparatus. The methylene chloride was then disposed of as organic waste in the organic waste container. The residue in the round bottom flask was scraped off, put in a separate container and the boiling chips were disposed of. Sublimation The purpose of this step was to obtain the pure caffeine from the solution. To do this, we set up a sublimation apparatus in the hood. The stopper on the round bottom flask was removed and the flask was attached to the apparatus. A heating mantle was placed under the container containing the residue from the previous step and cotton was put around the container to prevent it from burning. The water and the vacuum were turned on and the heating mantle was turned on. The system was left to run until crystals of caffeine were formed. The heating mantle was then turned off. The container was left to cool and the crystals were then scraped from the inside of the container and put in another container for storage. Thin Layer Chromatography The purpose of this step was to determine whether or not the caffeine was isolated. To do this, we prepared 3 solutions; ‘pure’, ‘crude’, and ‘Isolated’. We did this by pouring 3 mL of methylene chloride a separate container with the pure caffeine, using 3mL of the liquid in the flask from the previous step that was rinsed with acetone, and pouring 3 mL of methylene chloride into a separate container containing the caffeine we produced in the experiment. Two plates were then prepared by marking two horizontal lines and marking the starting points of the three solutions. Then the three samples were put on the matte side of the place using a capillary. This was then gently placed in a glass container containing 3 mL of ethyl acetate. The plate was left in there until the liquid level reached the top marking on the plate. The plate was then taken out, air dried, and then put under UV light for further examination. Results These are the results from the TLC

Solution = 9.35cm Isolated = 1.55cm Crude = 1.7cm, 6cm, 6.8cm Pure = 1.30cm Rf values: 1.55 cm =0.16578 9.35 cm 1.7 cm =0.18182 Crude Caffeine 1 = 9.35 cm 6 cm =0.64171 Crude Caffeine 2 = 9.35 cm 6.8 cm =0.72727 Crude Caffeine 3 = 9.35 cm 1.30 cm =0.13904 Pure Caffeine = 9.35 cm Isolated Caffeine =

This result shows that pure caffeine is a very polar molecule because it had the lowest Rf value. This means that it moved the shortest distance due to its polar bonds interacting with the polar bonds of the TLC plate. We can tell that crude caffeine is weakly polar, hence why it traveled a distance on the TLC plate. The experiment also shows that caffeine is an active ingredient in tea bags.

Discussion We concluded that the product we had formed through this experiment was indeed caffeine. However, we produced, much less than anticipated. This could be because of many reasons. One major reason would be because we didn’t let the tea solution cool down to room temperature before adding Methylene chloride. When we added Methylene chloride to the warm tea solution, there was a somewhat violent reaction and the tea solution appeared to start boiling even though it was already taken off the heating plate. We then had to add a lot more ice to make sure that the solution was cooled below 25 degrees. I believe this misstep resulted in the loss of some solution. We could also have measured the reactants wrong, resulting in a lower yield. Or we could have missed something in the setup of the apparatuses used throughout the experiment. Questions 1. Why does the addition of salt to the aqueous layer sometimes help to break up an emulsion which forms in an extraction? The salt increases the ionic strength of the aqueous layer that pushes the organic compound more into the organic layer. This is known as the “salting-out effect” 2. Why is the water solution cooled to 15-25° C before the Ch 2Cl2 is added? It must be cooled since the boiling point of Ch2Cl2 is 40° C, so if the water solution is too hot a dangerous situation could arise because ethylene chloride is a volatile at high temperatures.

3. What is the purpose of adding filter paper to the TLC chamber? The purpose of adding filter paper to the TLC chamber is to absorb the liquid and assists in creating an environment within the chamber that is saturated with the solvent. When the environment is saturated by the solvent, the TLC experiment occurs much more quickly, which is important when time is crucial. 4. What will happen if the level of ethyl acetate in the TLC chamber is above the base line you draw on the TLC plate? If the level of ethyl acetate in the TLC chamber is above the base line drawn on the TLC plate then the solvents could dissolve off of the TLC plate and into the solvent pool instead of eluting up the plate as preferred, rendering the plate useless and yielding no data.

Conclusion Overall, the lab went well except for the little misstep we had that significantly lowered our yield. The Rf values were not expected to be this low, but they are somewhat similar which means that there was a positive relationship between the pure, crude, and isolated caffeine.

References Ngozi, O. Experiment 1: Isolation and Purification of Caffeine. In Organic Chemistry II Laboratory Manual; New Jersey Institute of Technology: Newark, NJ, 2017; pp 4-13. (assessed September 2017) Tello, J. Extraction of caffeine from Robusta coffee (Coffea canephora var. Robusta) husks using supercritical carbon dioxide. [Online] 2011, 53-60. Amrita University. Extraction of Caffeine from Tea. 2013. http://amrita.vlab.co.in/? sub=3&brch=64&sim=169&cnt=1 (accessed Oct 7, 2013)...