CHEM 30ALSPRING 2002CHEM 30AL Spring 2002CHEM 30AL Spring 2002Postlab Guidelines - This is an individual reportCHEM 30AL SPRING 2002 EXPERIMENT #13: EXTRACTION AND PURIFICATION OF CAFFEINE FROM TEA LEAVES PRELAB GUIDELINES NOTE: There is ONLY ONE PRE-LAB for this experiment even though this is a 9-hour lab (3 lab periods). 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. 2. Prepare a flow chart 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. NOTE: Make sure that you look for organization of ideas and not just a copy of the procedure in boxes. 3. 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 (phase 1) and benzene (phase 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 (phase 1) and water (phase 2), 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?CHEM 30AL SPRING 2002 Report Guidelines for EXTRACTION AND PURIFICATION OF CAFFEINE FROM TEA LEAVES EXPERIMENT Study Questions (Continue): (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 of 3 (in favor of the ether). What simple method can be used to increase the partition coefficient? Explain.CHEM 30AL SPRING 2002 Report Guidelines for EXTRACTION AND PURIFICATION OF CAFFEINE FROM TEA LEAVES EXPERIMENT POSTLAB GUIDELINES - THIS IS AN INDIVIDUAL REPORT (A) Abstract Outline the objective of the experiment as well as any experimental results that obtained. Include any technique that you used in the lab to isolate, purify and analyze the experimental products. (B) Data and Data Analysis (i) Record all observations. (ii) Use equations to help explain any chemical reactions.or explain the phenomenon (physical changes)behind each of your other observations. (iii) Calculate the % caffeine that you recovered from tea. (iv) Mass Spectrum of caffeine: (i) identify the base peak. (ii) identify the molecular ion peak. (iii) does the molecular ion peak confirm the present of caffeine? Explain. Note: We will discuss mass spectroscopy at the end of the quarter. At this point, use the following definitions to answer the questions related to mass spectrum of caffeine. Base peak is the signal on the mass spectrum that has the highest intensity (or 100% on the y-axis) Molecular ion peak refers to the signal on the mass spectrum that gives you the molecular mass of the sample. Simply look at the x-axis (which is the mass) and look for a signal that give you the molecular weight of caffeine. (v) Calculate the Rf values of BOTH the pure caffeine and the crude caffeine. Show all your work. Note: Read pages 697-708 in Pavia about the concepts in Thin Layer Chromatography (TLC) . Pay special attention to pages 706-708 on how to find Rf value and what it means. I will explain TLC later on in the quarter. (C) Conclusion (i) Compare your % caffeine value to the reported value of about 2-4% caffeine content in tea leaves. Explain what may cause the % to be differed (i.e. where the loss of caffeine may come from during the experiments). (ii) Compare experimental IR spectrum to literature IR spectrum (provided with the experiment #14 worksheets). What can you conclude about the purity of your product.(iii) Interpretation of caffeine product composition and purity from TLC results. Explain all your reasoning. NOTE: Before answering part (iii), refer to the notes on TLC listed
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