UCLA CHEM 14CL - Report Guidelines for Extraction of Caffeine7a (4 pages)

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Report Guidelines for Extraction of Caffeine7a



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Report Guidelines for Extraction of Caffeine7a

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Pages:
4
School:
University of California, Los Angeles
Course:
Chem 14cl - General and Organic Chemistry Laboratory II
General and Organic Chemistry Laboratory II Documents
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CHEM 14CL WINTER 2006 EXPERIMENT 7A 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 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 1 31 and 2 1 depending on when your section meets Part 4 study questions is DUE on 2 2 and 2 3 depending on when your section meets NOTE There is ONLY ONE pre lab report 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 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 4 Study Questions Complete the following questions MUST SHOW ALL WORK FOR FULL CREDIT Note Kp is equivalent to 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 CHEM 14CL WINTER 2006 EXPERIMENT 7A 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 Continue 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 CHEM 14CL WINTER 2006 Report Guidelines for EXTRACTION AND PURIFICATION OF CAFFEINE FROM TEA LEAVES EXPERIMENT POST LAB REPORT GUIDELINES THIS IS A GROUP REPORT Post lab report must be written inside your lab notebook 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 Observations and Data Analysis i Recopy all observations as well as numerical data in an organize manner ii Use equations to help explain any chemical reactions that occur during the experiment and explain the phenomenon physical changes behind each step of the observation 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 v UV Spectrum of caffeine Calculate the molar extinction coefficient for caffeine Show all your work Note Assume the diameter of the cell holder to be 1 cm Note We will discuss mass spectroscopy later on in the course 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 with respect to 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 gives you the molecular weight of caffeine vi Calculate the Rf values of BOTH the pure caffeine and the crude caffeine Show all your work Note Read pages 153 162 in Mohrig Techniques on Organic Chemistry about the concepts in Thin Layer Chromatography TLC Pay special attention to pages 154 155 on how to find Rf value and what it means Concepts behind TLC will be discussed later on in the course CHEM 14CL WINTER 2006 Report Guidelines for EXTRACTION AND PURIFICATION OF CAFFEINE FROM TEA LEAVES EXPERIMENT POST LAB REPORT GUIDELINES THIS IS A GROUP REPORT Post lab report must be written inside your lab notebook 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 Note If you don t have the literature caffeine IR spectrum go to the following Web site and download the IR spectrum http webbook nist gov chemistry Do a NAME search on caffeine and there should be a hyperlink for the gas phase IR spectrum of caffeine 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 on the previous page of this guideline Attach ALL the spectra the experimental TLC plate with your post lab report


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