Chem 336 - Spring 1999 - Organic Chemistry III
Portland State University - Dr. Carl C. Wamser

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Chapter 21 Homework Answers

Brown & Foote, pages 874 - 882:
Problems 21.15 - 25 , 28 - 32 , 34 , 45 , 46

1. Write all the resonance forms for protonated imidazole. One is shown below.

Note that the positive charge does not show up on the other two carbon atoms.

2. Predict whether the following acid-base equilibria would be more favorable to the right or to the left. Use pKa data from your text.

a)

to the right (aliphatic amines are stronger bases than aromatic amines)

b)

to the left (with a pKa about 4, it is neutral above pH 4)

c)

to the right (with a pKa about 10, it is protonated below pH 10)

3. Given an optically active sample of 1-amino-1-phenylethane, write a series of reactions that could be used to resolve a racemic mixture of 2-methylbutanoic acid.