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Problems Set #7
General announcements:
1. Waste management and lab safety
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.
c. You are not allowed to wear gloves outside the lab. This applies in particular to the office suite in which the instructor resides since this poses a significant health risk for everybody in the suite. Another bad habit is to bring solutions and chemicals to the instructor's office, which is a no-no as well.
2. The next quiz (=quiz 3) will be administered on Tuesday, April 21, 2009 at 12 pm covering the catalyst and epoxidation (experimental and theory for both). Please make sure that you show up on time, which means at 11:55 am. Otherwise you will not be allowed to take the quiz.
3. After the quiz there will be a Chemdraw training in the SLC.
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 April 24, 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 here, the more feedback you will get, which will beneficial for the final version. We will try to return the reports by Monday.
5. The draft has to be submitted in a folder. Copies of all spectra have to be included into the draft.
6. It also came to the attention of the instructor that students are sharing data. To make it very clear, this is not allowed and will be regarded as cheating independent from what the TA told the students.
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. Flash chromatography
a. Why is the dry packing of the column preferential in the lab? Which precaution have to be taken during the packing?
b. What is the function of the cotton ball and the sea sand on the bottom of the column? How much of each is added?
c. After packing the column, a student that usually uses the lecture to catch up with sleep, wets the column using the dichloromethane. The instructor notices this and gets on his case. Why?
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? Show a balanced chemical equation.
e. Which solvent is used as mobile phase to elute the column?
f. How does the experimenter know which fractions contain the desired epoxide?
2. NMR spectroscopy
a. Which and how much solvent should be used to prepare the NMR sample?
b. How much sample should be placed 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?
3. GC/MS chromatography
a. What is the proper concentration of the sample to be submitted?
b. Which solvent is used here?
c. Which information does the student obtain from the GC spectrum?
d. Which information does the student obtain from the MS portion?