Extraction and Purification of Caffeine from Tea Leaves | CHEM 30AL, Lab Reports of Chemistry

Download Extraction and Purification of Caffeine from Tea Leaves | CHEM 30AL and more Lab Reports Chemistry in PDF only on Docsity! CHEM 30AL SPRING 2009 EXPERIMENT # 13: EXTRACTION AND PURIFICATION OF CAFFEINE FROM TEA LEAVES Experiment #13 IS AN INDIVIDUAL WORK & REPORT IMPORTANT: Make sure that you follow the proper laboratory safety protocol (refer to the course syllabus) BEFORE going to the lab. You will be dismissed from the laboratory if you do not follow the proper safety protocol. There is ONLY ONE pre-lab report for this experiment even though this is a 9-hour lab (3 lab periods). (I) On-line Resources For This Experiment: Please go to chem. 30AL VOH page under Web links and click on Way to Downloading appropriate Video to view the following: •Extraction procedure •TLC Procedure on this Orgchem site (II) PRE-LAB REPORT GUIDELINES (PRE-LAB REPORT MUST BE WRITTEN INSIDE YOUR LAB NOTEBOOK) NOTE that ONLY parts 1, 2 and 3 are DUE on 4/14 & 15 depending on when your section meets. Part 4 (study questions) is DUE on 4/16 & 17 depending on when your section meets. 1. Introduction - list the goal(s) of the experiment as well as any experimental techniques that will be used during the experiment for purification and/or identification. Include references and the changes to the procedure noted below: CHANGE IN THE LAB PROCEDURE On page 115, make the following changes to the LAST SENTENCE in the last paragraph: Instead of “Add the 1-propanol from the first two extractions to the funnel” Replace it with “Add the 1-propanol from the last 2 extractions to the same beaker used previously to store the other 1-propanol layers.” Also on page 115, in the last paragraph, the drying agent will be anhydrous sodium sulfate and NOT anhydrous sodium sulfite. On page 116, in the middle of the second paragraph replace "Repeat the extraction 2 more times with an additional 10mL of acetone each time,...." with "Rinse the NaCl precipitate in the beaker 2 more times with an additional 10mL of acetone each time...." 2. Flowchart - Prepare a flowchart of procedures AND show the location of the caffeine throughout each step of the experiment in the flow chart. Make sure you also REFERENCE the procedures. 3. Set up BLANK DATA tables for recording any numerical values AND in-lab observations. (Use a NEW page for the tables). IMPORTANT: You MUST record ALL the observations during the lab period for this experiment in your notebook. Failure to do so will result in no credit for your lab technique as well as part of your post-lab report. NOTE: Make sure that you look for organization of ideas and not just a copy of the procedure in boxes. CHEM 30AL SPRING 2009 EXPERIMENT #13: EXTRACTION AND PURIFICATION OF CAFFEINE FROM TEA LEAVES IMPORTANT: Make sure that you follow the proper laboratory safety protocol (refer to the course syllabus) BEFORE going to the lab. You will be dismissed from the laboratory if you do not follow the proper safety protocol. 4. Study Questions Complete the following questions. (MUST SHOW ALL WORK FOR FULL CREDIT). Note: Kp is equivalent to α (refer to lecture guide for definitions and the necessary equations to complete the study questions). (a) You wish to extract an organic compound from an aqueous phase into an organic layer (three to six extractions on a marcoscale). With regard to minimizing the number of transfer steps, would it be better to use an organic solvent that is heavier or lighter than water? Explain. (b) A compound distributes between water (solvent 1) and benzene (solvent 2) with Kp = 2.7. If 1.0g of the compound were dissolved in 100mL of water, how much compound could be extracted by THREE 10-mL portions of benzene? (c) If the value of Kp is 0.5 for the distribution of a compound between pentane (solvent 2) and water (solvent 1), and equal volumes of the two solvents were used, how many extractions of the aqueous layer will be required to recover at least 90% of the compound? (d) Calculate the % of a compound that can be removed from liquid phase 1 by using ONE to FOUR extractions with a liquid phase 2. Assume that Kp = 2 and the volume of phase 2 equals to 50% that of phase 1. (e) A slightly polar organic compound distributes between diethyl ether and water with a partition coefficient equal to 3 (in favor of the ether). What simple method can be used to increase the partition coefficient? Explain. NOTE: You MUST turn in this pre-lab report to your TA at the BEGINNING of the lab on the dates listed above even if you finished the entire experiment in ONE lab period. Pre-lab reports will not be accepted at other times or locations.