Work Completed: 01.22.09 Work Submitted: 02.03.09 Synthesis 0732: Isolating Caffeine from Tea Abstract Caffeine was extracted from instant tea and purified by recrystallization. The yield was determined to be 1.2152 % of per one gram of instant tea. Introduction In this experiment, will be extracted from instant tea. The will be purified by recrystallization and the percent mass of per gram of instant tea will be determined. Students will perform the following experiment to determine how much is in one gram of a typical caffeinated beverage such as instant tea. bjectives: 1. To extract from tea 2. To perform a vacuum filtration 3. To separate layers from a crude extract 4. To purify by recrystallization 5. To determine the percent of per gram of instant tea Descriptions Caffeine is a natural product belonging to the alkaloid group. Caffeine is a stimulant and has some undesirable side effects where an individual has a physical dependence to this chemical. Many of the earliest isolated pure compounds from plants were alkaloids because of the ease of isolation. This is because a nitrogen atom generally makes the compound basic and the compound exists in the plant as a salt. Most alkaloids are extracted with water or weak acid and recovered as crystalline material by treatment with base. The following flow chart outlines a typical extraction of the stimulant from its natural alkaloid state. rganic Chemistry II, Lab Report 2 Page 1
Flow chart: Isolating Caffeine from Tea Tea + dichloromethane (DCM) + 2M a Extract Tea + dichloromethane (DCM) + 2M a Separate rganic Layer - DCM + Caffeine Aqueous Layer a Discard Collect Excess DCM Distill Caffeine + small amount of DCM Crude Caffeine Caffeine + 2-propanol Add 2 propanol, eat (hv) Cool Cooled Caffeine + 2-propanol Evaporate Remaining DCM into the atmosphere Add exane, Filter Caffeine Crystals Structural formulas of some xanthine alkaloids: Xanthine Caffeine Theophyline Theobromine rganic Chemistry II, Lab Report 2 Page 2
3 2 4 5 6 7 1 11 10 8 9 3 2 4 5 6 7 1 10 8 9 Materials: Figure 1 Distilling Apparatus Thermometer Water ut Condenser Water In ickman Still ead Conical Vial Sand Bath eat Source Stirring Apparatus Students will use the distilling apparatus to separate the and DCM. Table 1 List of Materials and Equipment List of Materials 1. Instant tea 2. Dichloromethane 3. 2M a 4. 2-propanol 5. exane 6. Anhydrous sodium sulfate To isolate purified To extract the To extract the To recrystallize To wash the purified crystals Drying agent List of Equipment 1. Round bottom flask 2. Phase separation paper 3. irsch funnel with adapter 4. ot plate To mix tea, a, and DCM To separate the from the tea, a, DCM mixture To filter crystals For hot water bath rganic Chemistry II, Lab Report 2 Page 3
Procedural Steps: 1. Mix tea 2. Separate aqueous and organic layers 3. Distill 4. Evaporate to crude 5. Dissolve and recrystallize 6. Filter purified 7. Record mass of crystals Data and Results Table 2 Data and Results Mass Instant Tea Mass Recovered Caffeine Crystals 1.0122 g 0.0123 g Calculations: (Eq. 1) = 1.2152 % Discussions and Conclusions By calculation, the amount of per one gram of instant tea was determines to be 1.2152 %. This data may be imprecise because during the extraction of, emulsions may have occurred. This happens when an organic compound of one liquid in a second liquid and the first compound will not mix such as a case with water and oil. Because of this, during phase separation, a arbitrary amount of was separated depending on how gentle students shook the mixture. In this experiment, was extracted from instant tea using an aqueous solution of sodium hydroxide and hexane. Sodium ydroxide was used to prevent the extraction of acidic compounds called tannins from the tea leaves. Caffeine is more soluble in an organic solvent, which is why dichloromethane was used instead of water to extract the organic solvent and separate it from glucose, tannins, and other water soluble compounds. rganic Chemistry II, Lab Report 2 Page 4
References McMurry, John, rganic Chemistry 7 th edition, Thompson Learning Inc. Books/Cole 2008. Silberman, Robert. Isolating Caffeine from Tea, page 65-73, Signature Lab Series, CE 2403, Cengage Learning. Mason, hio: 2008. Wu, Jennifer CE 2403 Signature Lab Series Page 65-73. rganic Chemistry II, Lab Report 2 Page 5