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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 10-24-2008 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.
2. The third quiz will be administered on Thursday, October 16, 2008 at 12 pm covering the catalyst and epoxidation. Please make sure that you show up on time. Otherwise you will not be allowed to take the quiz.
3. 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.
1. Referring to the catalyst design, answer the following questions.
a. What is the function of the tert.-butyl groups in the catalyst?
b. Why is the function of the cyclohexane ring?
c. What species transfers the oxygen to the alkene? How can teh structure of this species be described?
2. Referring to the epoxidation reaction carried out in the lab, answer the following questions.
a. The reaction is carried out as a biphasic reaction. Which two solvents are used in the reaction?
b. Why is it important to use a buffer? Which one is used?
c. The student starts off with a solvent mixture (dichloromethane:hexane=1:1) for TLC. The procedure asks to optimize the mixture? What does this mean and how is this accomplished?
d. A student is asked to use 6 mol% of the catalyst in the reaction. How much does he have to use (based on the numbers given in the reader)? Why is it not advisable to reduce the amount of catalyst significantly?
e. Why is it imperative to do the workup after the reaction is completed?