Organic Chemistry: Techniques and Transformations

This part should be filled in after the completion of the experiment and analysis of all data. When submitting the report, the abstract should appear at the beginning of the report. Report Adhere to the format required by your instructor and submit the report on time. Summary 1. Chromatography is a separation technique used to isolate a pure compound from a mixture using the difference in polarities of the various compounds. 2. Thin Layer Chromatography is a separation technique wherein a mixture of compounds can be separated into its individual components based on the difference in polarity of the compounds. The stationary phase used is silica and the mobile phase is in general, an organic solvent or a mixture of organic solvents. 3. Given a mixture of compounds, you should be able to predict how the mixture will appear if spotted and developed on a TLC plate (the separation will be based on the polarity of the compounds and the solvent used as well as the nature of the TLC plate). 4. Given an unknown sample, you should be able to figure out what it is by spotting it with and comparing it to the standard samples. 5. Know how to calculate Rf values. 6. A more polar developing solvent will make the spots move further up on a TLC plate (know why). 7. A more polar compound will stick more to a normal phase TLC plate and move slowly than a relatively less polar compound (know why). 8. You used short-wave UV light to visualize the TLC plates, after developing. Organic Chemistry: Techniques and Transformations 7 Questions Your instructor may assign some or all of these questions as preor post-Laboratory assignments. 1. Indicate which property of compounds is responsible for the separation in a TLC. 2. How does the separation occur during a TLC? 3. Name 3 adsorbents used in TLC. 4. Define eluent. 5. Indicate 3 ways of visualizing a TLC after elution. 6. Define Rf. 7. Name three other types of chromatography. 8. Indicate 3 uses of Thin Layer Chromatography 9. (a) A student performed a thin layer chromatographic separation experiment. In the first run, four standard substances A – azobenzene, B – benzoin, C –cinnamic acid, and D – dextrose were spotted on the plate. The line indicates the solvent front. In the second TLC run a mixture (X) of two of these same substances was separated. Based on Rf values, what is the identity of the unknown mixture X? (b) A second mixture, Y, was run at the same time. What is wrong with the solvent system used to try to separate Y? 10. A student was asked to spot the following three compounds on a TLC plate and develop it. Show the diagram of the developed TLC plate appropriately labeled.