Nguyen 3Extracting Caffeine ReportKatherine NguyenTuesday, January 23, 2018SCH4UMr. HathawayDisclaimer This report comes from the observation of a Dichloromethane (DCM) method extraction of caffeine from a tea video (link for the video is in the bibliography number #). All observations made are directly from the video or from other reports about caffeine extraction. In addition, no results section will be added due to lack of quantitative data.Introduction Tea has a rich and deep history in many cultures. This beverage, to this day, still remains current and ever evolving. It was first harvested by the Chinese about 2,000 years ago. Many different techniques were used to enhance the tea plant’s, camellia sinensis, flavor (BK, 2010). From creating hybrid combinations to fermenting, the same leaf can be changed to create millions of different teas. As time passed, the British Empire became the largest producer of tea. This came about after the colonization of India which provided them with space for large tea plantations. Tea spread to other countries and became a worldwide sensation. The Japanese use it for ceremonies and it now provides households with a daily routine (Weaver, 2017). Figure 1 – Caffeine Blocking AdenosineCaffeine has a bitter taste and is said to make up 5% of a whole tea leaf (OCL, n.d.). In its pure form is an odorless white powder (PubChem, n.d.). It is a methylxanthine alkaloid that is primarily found in organic material like seeds, plants, and leaves. Caffeine, like other alkaloids, are also able to stimulate a variety of systems in the body like respiratory, cardio vascular and the nervous system. Stimulating all of these systems, tea is able to delay fatigue. Caffeine is able to bind to the adenosine receptors in the brain and block their activity. Normally, the adenosine slows down the receptors, therefore, slowing the activity in the body like during sleep. Caffeine is able to completely block these receptors and allow the hormone epinephrine to be released. This hormone is able to “higher heart rate, increase blood pressure, increase blood flow to the muscles and decrease blood flow to the skin and inner organs, and release glucose by the liver” (OCL, n.d.). This results in an alert and awake body that is commonly found when drinking a black coffee.Purpose The purpose of this lab is to extract caffeine from 4 bags of tea using the liquid-liquid extraction method. Hypothesis I hypothesize that caffeine will be extracted from the tea successful using the DCM method. One bag of tea is able to make about 30 – 70mg of caffeine(OCL, n.d.). The expected yield from 4 bags of tea would be 120 – 280 mg of caffeine.Material – 45 ml dichloromethane- Water – 4 bags of Green tea – 6g Na2CO3 Procedure 1. 4 bags of green tea, 90ml of water and 6g anhydrous sodium carbonate was placed in a beaker and a lid was added 2. The mixture gently boiled for 10 minutes, until it was a deep brown colour, occasionally the lid was removed when the mixture bubbled3. The mixture was removed to an Erlenmeyer flask and the tea bags were squeezed to release as much liquid as possible. 4. 60ml of water was added back into the beaker with the tea bags and steps 2 -3 were repeated 5. The resulting mixture was added to the Erlenmeyer flask 6. The mixture was allowed to cool to room temperature 7. The mixture was filtered through filter paper and celite to remove any additional substances 8. The mixture was transferred from the Erlenmeyer Flask to a separatory funnel with two support rings 9. 15ml of Dichloromethane was added to the mixture and shaken 10. After the mixture settled and created 2 layers. The dichloromethane was drained11. Steps 9 – 10 were repeated 2 more times12. A small amount of sodium sulfate was added as a dehydrating agent leaving a crud layer13. The mixture was filtered into a round bottom flask with more dichloromethane14. A distillation was set up to remove the dichloromethane leaving crud caffeine at the bottom of the round flask15. The solution was then heated to remove additional dichloromethane 16. 95% ethanol was added to the cooled solutions to recrystallize the caffeine17. The mixture was vacuum filtered and washed with 95% ethanol 18. These crystals were drained under a vacuum Discussion Green tea was chosen as the tea to extract the caffeine from. This was probably chosen due to convenience vs caffeine concentration. It is a misconception that teas like black have more caffeine than other teas like white or green. The flavors are determined by the preparation but the preparation does not determine the concentration. The only difference would be if a herbal tea was used. Unlike green or oolong tea, herbal teas come from flowers which do not contain caffeine or too little to have any affect. Figure 2 PurineCaffeine has a unique structure that allows it to attach to the body from the nervous system to the cardiovascular system. This comes from the hydroxylic base, two ring structures, family called the purine (Britannica, 2017). In its most basic form, it is made up of carbon, nitrogen, and hydrogen. These atoms were joined together with three different functional groups: an amine, amide and an alkene (Postu, 2013). As shown in figure 2, the structure is not symmetrical due to lone pairs off the nitrogens creating negative regions, dipole-dipole interaction, and it is dispersion forces that result from the shape and covalent bonds. Caffeine’s polar properties allow it to bond with the hydrogen in water but its structure makes it not very soluble. In addition to the caffeine, there are two other components that are stored in the tea leaves, cellulose, and tannin. Cellulose functions as the structure of the leaves but is ultimately insoluble in water (BK Rev, 2010). The cellulose does not affect the results as it is the loose leaves that are strained out of the mixture in the beginning. Tannin, on the other hand, is very soluble in water and slightly soluble in dichloromethane. Tannin comes in two different forms condensed and hydrolyzable. Condensed Tannin is derived from natural substances like the wood or bark of mangrove and wattles (Britannica, 2016). It is a dimer, two identical molecules linked, which “are usually linked by carbon-carbon bonds between carbon-4 and carbon-8 of two flavan-3-old” (Hil, 2003). These bonds are very strong and stable, therefore, condensed tannin usually comes in the form of a red precipitate that is insoluble in water. The hydrolyzable tannin form is most commonly found in Chinese or Turkish nutgalls, buds (Britannica, 2016). These are made up of gallic acid chains and a glucose core (Hil, 2003). This form can decompose in water and is able to react with other substances. At room temperature water doesn’t do a very good job dissolving organic materials like caffeine. Due to caffeine’s structure it can only become soluble in solvents that are polar aprotic (OCL, n.d.). This means that water, a protic solvent, has a hard time dissolving caffeine (Libretext, 2015). In order to extract the caffeine, it has to be forced out of the leaf. Caffeine has a solubility of 2.26g/100g in water at 25* but at 100* it has a solubility of 67g/100ml. When water is heated, the molecules increase in energy and become more active. As the energy and the motion increases so does caffeine’s ability to bond to the hydrogen in the water. Tannin, soluble in protic solvents, is able to easily dissolve into water. Heating the water extracts the tannin and the caffeine from the leaves leaving only the cellulose. Figure 3 Sodium CarbonateSodium carbonate was also added to the heated water for several reasons. The first reason is to prevent the caffeine from reacting and forming any cations. Sodium carbonate is a base and is able to neutralize any acid present in the solution (Weaver, 2017). Caffeine is mostly basic and becomes more soluble in low Ph solutions, however, this reaction creates protonated salts and becomes more hydrophilic (SendersReagent, 2015). The sodium carbonate is able to prevent the formation of these cations and also make it easier for the caffeine to bond with the dichloromethane (Postu, 2013). The second reason is to remove the tannin from the mixture. As the sodium carbonate, a base, (as shown in figure 3), is added to the tannin, an acid, the acidic aromatic rings known as phenolic groups will react to neutralize (Weaver, 2017). This reaction will form ionic bonds between the sodium carbonate and the tannin to create a salt that is soluble in water. However, this new salt is not soluble in dichloromethane and will remain in aqueous form during the extraction. This also aligns with the fact that tannin is soluble in mostly protic solvents. When the dichloromethane is added to the separatory funnel its heavy density, 1.325g/m, allows it to sink to the bottom creating the organic layer (Postu, 2013). The caffeine and tannin salt is left to cool back to room temperature. As dichloromethane has a boiling point of 39.60 ° C, the cooling allows them to combine with ease without boiling the dichloromethane (PubChem, n.d.). Caffeine solubility in dichloromethane is 8.45g/100ml, significantly larger then caffeine solubility in water (Weaver, 2017). This is due to the distribution constant between water and dichloromethane. The distribution constant is measured by the solute in the organic phase, dichloromethane layer, divided by the solute in the aqueous phase, the tea water layer. These concentrations aren’t known but because the ratios between concentration and solubility are similar the solubility can be used as a substitute. The value of Kd can determine which solvent the solute prefers. If the Kd value is greater then one the solute prefers the organic phase and the solute can be extracted from the aqueous phase. If the Kd value is lesser then one the solute prefers the aqueous phase and will not transfer to the organic layer (ChemistryConnected, 2012). Substituting the concentrations for solubility, the distribution constant is (Kd = 8.45 /2.26) 3.74 (Weaver, 2017). The distribution constant shows that the caffeine is 4-time soluble in the dichloromethane then in the water and will definitely be transferred. The dichloromethane step is repeated 3 times to efficiently extract the caffeine from the aqueous solution. During the experiment, the separatory funnel was shaken periodically to prevent emulsion. An emulsion is very common in liquid-liquid reactions and probably appeared in this experiment. This happens when two liquids that are insoluble in each other are mixed. This results in little droplets suspended in the middle of the solution (Weaver, 2017). Figure 4 Sodium SulfateAfter all of the caffeine is extracted from the aqueous solution the water and dichloromethane must be removed. Sodium Sulfate is added to the solution to remove the water. Sodium sulfate is a very commonly used drying agent, an anhydrous organic salt (as shown in figure 4). When added to the solution it is able to remove water by binding with it and becoming hydrous once again (Postu, 2013). This is very efficient but in order to remove the dichloromethane, the solution must be put on a heating mat to evaporate remaining dichloromethane. This creates a white crud that is then refiltered and washed to create the purist caffeine. It has a crystal shape and remains pure white as shown in figure 5. This shows that no tannin was also extracted.Figure 5 ResultsThough the experiment was successful and resulted in pure caffeine the predicted yield was very off. The predicted yield was 200g but the total yield was 30mg. When tested, the result of the NRM are very similar to pure caffeine. Comparing figure 6 to figure 7, they are almost identical. This shows that the experiment made pure caffeine.