the lab (20 pts) Post-Lab Questions 1. (5 pt s) Th is reaction works with trans-
ID: 551617 • Letter: T
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the lab (20 pts) Post-Lab Questions 1. (5 pt s) Th is reaction works with trans-cinnamic acid. Using your knowledge of Thin Layer Chromatography, why is t identificaio wth wto?s rans-cinnamic acid not a good potental subsrate for rans-cinnamic acid not a good potential substrate for OH trans-cinnamic acid 2. (5 pts) When the catalyst was added to the reaction, you should have observed a color change. Describe what is happening on a molecular level to cause the reaction mixture to change colors. a. Hint: DBDMH is the brominating agent in this reaction and is depicted below; the key to this problem is to think about how the catalyst would interact with this substrate O Br Br-N DBDMH 3. (10 pts) Using your knowledge of the structure of trans-cinnamic acid, explain why the bromine atoms add anti across the alkene. Draw a mechanism and explain. i. Your answer should be informed by the following: a. Bromonium ion formation b. Steric hindrance c. Oxymercuration-demercuration mechanismExplanation / Answer
1- reason for fail to identify the trans cinnamic acid on TLC is given below-
By use high polar/nonpolar ratio of solvent (eluent) combination shuold use to run the TLC. The spot could not be clear on TLC, But show tailing on TLC plate because it could bind strongly on TLC silica gel.
Carbxylic acids(acid group) are highly polar compounds which do not move up very easily in most of the solvents. Thus as we run the tlc for the reaction, trans-cinnamic acid would sit at the base along with some other colored impurities of the reaction.
Acid group is highly polar group, thats why it could bind strongly on TLC, show tailing.
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