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Problems Set #7
General announcements:
1. Waste management
a. I noticed that many students pour acetone down the sink, which is entirely unacceptable according to California Law. If the authorities notice this, we will get fined $$$$$$.
b. Gloves and paper towel below in the regular trash and not into the box where glass waste is collected. Students throw the hot glass waste (from pulling capillaries in there and the paper might catch fire!). On the same token, glass waste belongs into the blue-white box and not into the regular trash.
2. The next quiz (=quiz 3) will be administered on Thursday, October 16, 2008 at 11 am covering the catalyst and epoxidation (experimental and theory for both). Please make sure that you show up on time. Otherwise you will not be allowed to take the quiz.
3. On Tuesday, October 21, 2008 the class will meet for lecture in YH 4335 and YH 4336 (Chemdraw training).
4. 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 here, the more feedback you will get, which will beneficial for the final version. We will try to return the reports by Monday.
ATTN: answers to the below questions are due at the start of your lab period of Meeting 7; these answers should be part of your pre-lab write-up.
1. The last step of the epoxidation involves flash chromatography.
a. What is the purpose of this step?
b. The column can be packed wet and dry. Why is the dry packing preferred here? Which precaution have to be taken during the packing?
c. What is the function of the cotton ball on the bottom? Does the student have to add one on the top as well?
d. Why is the stationary phase pre-treated with a 1% NEt3 solution in hexane? What would happen if the student neglects to perform this step?
e. Which solvent is used as mobile phase here?
f. Why does the experimenter have to use air pressure to elute the sample?
g. How can one find out which part of the eluent contains the desired epoxide?
2. NMR spectroscopy
a. Which solvent is used here?
b. How much sample should be in the NMR tube?
c. Where is the sample labeled? What is included into the label?
d. Which information can the student gather from the H-NMR spectrum?