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Unformatted text preview: Chem140C Spring Finn Midterm 2 Practice Problems Page 1 of 4 Chem 140C Spring 2008 (Finn) Midterm Exam #2, Practice Problems Note: Some of these problems are too difficult for me to give on a test you could do them, but it might take too much time. They are therefore excellent to help you prepare. 1. Draw the mechanism of each step in the two-step transformation: N O Ph H (1) Ph Br (2) base N Ph Ph O 2. Explain the trend in acidities of these protonated amines. N O H H N O H N H pK a = 0.8 pK a = 5.3 pK a = 11.0 3. The reaction of a hydrazine with an acetylenic ester gives a pyrazolone. Write a detailed mechanism for the formation of the pyrazolone in the reaction below. [For tautomerizations, write taut. For proton transfers within a molecule, write PT. Make sure you push arrows for all other steps.] (Hint: the reactivity of an ! , "- unsaturated alkyne is similar to that of an ! , "-unsaturated alkene.) EtO O + R H N NH 2 EtOH 80 C HN N O R a pyrazolone Chem140C Spring Finn...
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- Spring '06