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Problems Set #6
ATTN: answers to the below questions are due at the start of your lab period of Meeting 6; these answers should be part of your pre-lab write-up.
Announcements:
1. Make sure that you make progress on your formal report as well in terms of literature research and writing the parts that you completed already in the lab. The draft version of paper is due on October 23, 2009 at 5 pm. The draft version is worth 15 points, the final paper 45 points. For more information what the draft is supposed to contain see here. Late submission will receive less credit. The more of your work you submit in the draft, the more feedback you will get, which will beneficial for the final version. We will try to return the reports by Monday, October 26, 2009.
2. It is highly advisable to look at the reader prior to attending to lecture. There are a lot of issues to discuss in the individual experiments, but not enough time to discuss every little thing in great detail. It is also recommended to review the techniques that should be familiar to you from 30AL/BL i.e. extraction, recrystallization, TLC, IR/NMR spectroscopy, etc.
3. The second quiz will be administered on Tuesday, October 13, 2009 at 11:00 am covering the ligand and catalyst synthesis and characterization. Bring a ruler, non-graphing calculator and blue or black pen with you. Please make sure that you arrive on time (this means that you should be seated by 10:55 am!!!). Late arrivals will not be allowed into the class room since they disturb the rest of the class!! This also means that you will not be allowed to take the quiz!!!
4. There is no data sharing. Everybody has to acquire her/his own spectra and data i.e. malting point, optical rotation. Students who share data will be reported to the Dean of Students since this is be considered cheating.
5. The lecture for October 8, 2009 is canceled due to "personal obligations" of the instructor.
And now to the fun part...the prelab questions:
1. Referring to the catalyst design, answer the following questions.
a. What is the exact function of the tert.-butyl groups in the catalyst? What would happen if the were replaced by methyl groups?
b. What is the function of the cyclohexane part in the catalyst?
c. Why is manganese used as central atom here and not Mg?
d. How many products would be obtained if b-methylstyrene was used as reactant for the epoxidation? Explain.
2. Referring to the epoxidation reaction carried out in the lab, answer the following questions.
a. Why is the reaction carried out in a biphasic system?
b. Why is it imperative to use a buffer in this reaction?
c. In lecture it was emphasized that the reaction mixture should be worked up immediately after the reaction was completed. Explain.
d. The student starts off with a solvent mixture of dichloromethane:hexane=1:1 for TLC. The procedure asks to optimize the mixture. What does this mean and how is this accomplished? Why is this optimization important?
e. How are the alkene and the epoxide being visualized? Outline a brief procedure.
f. How does the crude product appear? How should it be stored?