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Meeting 15 (Acetyl Ferrocene)
Important Announcements:
1. The proposal is due on November 21, 2007 at 5 pm in YH 3077 E (If you have problems please see me asap!). Late proposal will not be accepted and will lead to an automatic "F"-grade for the course. The important references have to be attached to the proposal. The proposal has to be submitted to turnitin.com as well (same course ID as before) by 10 pm on November 21, 2007, only one per group! Make sure that you have an electronic copy of your proposal with you. The computer lab is closed over Thanksgiving!
2. The next quiz (=quiz 6) will be administered on November 19, 2007 at 10 am. It will cover the nitration reaction, the ferrocene reaction and the acylation reaction. Make sure that you show up on time. Otherwise you will not be allowed to take the quiz.
3. In the lab, you will only carry out the acylation of ferrocene, but not the synthesis of ferrocene. This part will be done individually and not in groups.
Homework assignments (due November 15/16, 2007)
1. Referring to the synthesis of ferrocene, answer the following questions.
a. Cyclopentadiene is not commercially available. How can it be obtained in the lab? Which precautions have to be taken?
b. Why is cyclopentadiene significantly more acidic than cyclopentane?
c. Why is DMSO used as solvent for the reaction?
d. The flask has to be closed tightly during the reaction. Explain briefly why.
e. The crude product is recrystallize from petroleum ether at T=-78 oC. Which problems do you anticipate here?
f. The 1H-NMR spectrum of ferrocene exhibits one signal at d=4.15 ppm. Rationalize this observation. How would the spectrum change if it was acquired at very low temperatures?
2. Referring to the synthesis of acetyl ferrocene, answer the following questions.
a. How is the acylium ion generated in the lab? Show pertinent chemical equation(s).
b. The acylium ion is considered a weak electrophile compared to the nitronium ion. Rationalize the difference and explain which consequence this have for the Friedel-Crafts acylation .
c. Which compounds does the reaction mixture contain after the completion of the reaction?
d. Why is it important to "neutralize" the organic layer before performing the column chromatography step?
e. Why is petroleum ether used in the beginning of the elution process and a mixture of petroleum ether and ethyl acetate later on?