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Meeting #13
General Announcements
1. The next quiz will be administered on Monday, November 13, 2006 at 12 pm. It will cover the Grignard reaction, esterification and nitration reaction.
2. Please look start looking for a partner for the last project. Your partner should be in a different time slot than yourself e.g. 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 will be due on November 22, 2006 at 5 pm.
3. If possible both reactions (esterification and nitration) should be carried out in this lab. This will give you more time to recrystallize the final product and get better quality crystals.
Homework questions
1. Referring to the esterification part of the project
a. What is the function of the sulfuric acid in this reaction?
b. Why is it imperative to dry the benzoic acid thoroughly before carrying out the esterification?
c. After the reaction is terminated, water is added to the cold reaction mixture. Rationalize this step.
d. The etheral layer is extracted with sodium bicarbonate during the work-up process. Explain and show pertinent equations.
2. Referring to the nitration experiment, answer the following questions.
a. Which function does sulfuric acid have in this experiment? Show pertinent chemical equations.
b. The nitronium ion is a very strong electrophile. Explain why and which implication does this have for the reaction carried out in the lab?
c. Why is a mixture of water and methanol (1:4) used for the recrystallization step?
d. What are the most important changes in the IR spectrum going from methyl benzoate to m-nitro methylbenzoate?
3. Referring to electrophilic substitution reactions in general,
a. Why is it necessary to protect a amino group when carrying out a nitration reaction using nitric acid as source for the electrophile?
b. How can one predict where an incoming electrophile will go preferentially if there are already two substituents on the ring?