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Meeting #12
General Announcements
1. The next quiz (=quiz 5) will be administered on Wednesday, February 17, 2009 at 11 am and will cover MS, GC and NMR spectrocopy of epoxides and the Grignard reaction. Make sure that you show up on time. Otherwise you will not be allowed to take the quiz.
2. The postlab report for this project is due on February 25 or February 26, 2010.
3. If possible both reactions (esterification and nitration) should be carried out during meeting 12. This will give you more time to recrystallize the final product and get better quality crystals. The final product has to be turned in to the TA by February 19, 2010 at 5 pm. Late submission will not receive any credit. Sorry! :-(
4. Please look start looking for a partner for the last project. Your partner should be in a different time slot than yourself i.e. if you are in T/R morning section, your partner should be in section in the T/R afternoon section or in the W/F afternoon section.
Homework questions
1. Referring to the Esterification carried out in the lab, answer the following questions. Show chemical equations and intermediates where appropriate.
a. Why is it imperative that the benzoic acid is as dry as possible for the reaction?
b. What is the function of methanol in this reaction?
c. Why is it necessary to reflux this mixture? What exactly does this mean?
d. After the reflux, the procedure asks to cool the reaction mixture first and then poured it into cold water. What is the purpose of this step?
e. Why are the combined the organic layers extracted with sodium bicarbonate? How does the student know that he is done with this step?
2. Referring to the Nitration reaction carried out in the lab, answer the following questions. Show chemical equations where appropriate.
a. What is the electrophile in this reaction? How is it obtained in the lab?
b. Why is it important to dissolve the ester in concentrated sulfuric acid prior to introducing the electrophile? Show the appropriate intermediate.
c. The reaction is carried out in an ice-bath. Rationalize this step.
d. The crude product is recrystallized. Which solvent is used? Rationalize the choice.