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Problem 31
A tertiary amine reacts with hydrogen peroxide to form a tertiary amine oxide.
Tertiary amine oxides undergo a reaction similar to the Hofmann elimination reaction (Section 10.10), called a Cope elimination. In this reaction, a tertiary amine oxide, rather than a quaternary ammonium ion, undergoes elimination. A strong base is not needed for a Cope elimination because the amine oxide acts as its own base.
Does the Cope elimination have an alkene-like transition state or a carbanion-like transition state?
Problem 32a,b
What products are obtained when the following tertiary amines react with hydrogen peroxide followed by heat?
a.
b.
Problem 32c
What products are obtained when the following tertiary amines react with hydrogen peroxide followed by heat?
c.
Problem 32d
What products are obtained when the following tertiary amines react with hydrogen peroxide followed by heat?
d.
Problem 33a
a. Draw resonance contributors to show why pyridine-N-oxide is more reactive than pyridine toward electrophilic aromatic substitution.
Problem 33b
b. At what position does pyridine-N-oxide undergo electrophilic aromatic substitution?
Problem 34
The chemical shifts of the C-2 hydrogen in the spectra of pyrrole, pyridine, and pyrrolidine are 2.82 ppm, 6.42 ppm, and 8.50 ppm. Match each heterocycle with its chemical shift.
Problem 36
Explain why pyrrole (pKa ~ 17) is a much stronger acid than ammonia (pKa = 36).
Problem 37
Propose a mechanism for the following reaction:
Problem 39a
Propose a mechanism for the following reactions:
a.
Problem 39b
Propose a mechanism for the following reactions:
b.
Problem 40a
What is the major product of the following reactions?
a.
Problem 40b
What is the major product of the following reactions?
b.
Problem 40c
What is the major product of the following reactions?
c.
Problem 40d
What is the major product of the following reactions?
d.
Problem 40f
What is the major product of the following reactions?
f.
Problem 42c
What starting materials are required to synthesize the following compounds, using the Fischer indole synthesis?
c.
Problem 44a
Show how the following compounds can be prepared from the given starting material.
a.
Problem 44b
Show how the following compounds can be prepared from the given starting material.
b.
