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Meeting #12
General Announcements
1. The next quiz (=quiz 6) will be administered on May 14, 2009 at 12 pm. It will the Grignard and the esterification reaction. Make sure that you show up on time. Otherwise you will not be allowed to take the quiz. Bringing a pruler and non-graphing calculator could not hurt either.
2. 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. The proposal for the independent project will be due on May 22, 2009 at 5 pm.
3. If possible both reactions (esterification and nitration) should be carried out during meeting 13. 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 May 15, 2009. Late submission will not receive any credit. Sorry! :-(
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. 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?
d. Afterwards, the aqueous layer is extracted with diethyl ether. 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 temperature has to be well controlled during the reaction. Why is this important and how is this accomplished?
d. The crude product is recrystallized. Which solvent is used and how does the final product look like?
e. What are the major changes in the IR spectrum going from methyl benzoate to the product of the nitration reaction?