Organic Chemistry

462 CHAPTER 12 Reactions of Alcohols, Ethers, Epoxides, and Sulfur-Containing Compounds

3-D Molecules:

[15]-Crown-5;

[12]-Crown-4

PROBLEM 24

Explain why the two arene oxides in Problem 23a open in opposite directions.

PROBLEM 25

Three arene oxides can be obtained from phenanthrene.

a. Give the structures of the three phenanthrene oxides.

b. What phenols can be obtained from each phenanthrene oxide?

c. If a phenanthrene oxide can lead to the formation of more than one phenol, which

phenol will be obtained in greater yield?

d. Which of the three phenanthrene oxides is most likely to be carcinogenic?

12.9 Crown Ethers

Crown ethersare cyclic compounds that have several ether linkages. A crown ether

specifically binds certain metal ions or organic molecules, depending on the size of

its cavity. The crown ether is called the “host”and the species it binds is called the

“guest.”Because the ether linkages are chemically inert, the crown ether can bind

the guest without reacting with it. The crown–guest complexis called an inclusion

compound. Crown ethers are named [X]-crown-Y, where X is the total number of

atoms in the ring and Y is the number of oxygen atoms in the ring. [15]-Crown-5

selectively binds because the crown ether has a cavity diameter of 1.7 to 2.2Å

and has an ionic diameter of 1.80Å. Binding occurs as a result of interaction of

the positively charged ion with the lone-pair electrons of the oxygens that point into

the cavity of the crown ether.

With an ionic diameter of 1.20Å, is too small to be bound by [15]-crown-5, but it

binds neatly in [12]-crown-4. On the other hand, with an ionic diameter of 2.66Å,

is too large to fit into [15]-crown-5, but is bound specifically by [18]-crown-6.

[12]-crown-4

cavity diameter = 1.2−1.5 Å

[18]-crown-6

cavity diameter = 2.6−3.2 Å

O

O

O O

O O

O O

O O

K+,

Li+

host

[15]-crown-5

cavity diameter = 1.7−2.2 Å

Na+ Na+

guest

O

O O

O O

inclusion compound

O

O O

O O

Na+

Na+

phenanthrene

For their work in the field of crown

ethers,Charles J. Pedersen,Donald

J. Cram, and Jean-Marie Lehn

shared the 1987 Nobel Prize in

chemistry.

Charles J. Pedersen (1904–1989)

was born in Korea to a Korean

mother and a Norwegian father.

He moved to the United States as a

teenager and received a B.S. in

chemical engineering from the

University of Dayton and an M.S. in

organic chemistry from MIT. He

joined DuPont in 1927 and retired

from there in 1969. He is one of the

few people without a Ph.D. to receive

a Nobel Prize in the sciences.

Jean-Marie Lehnwas born in

France in 1939. He initially studied

philosophy and then switched to

chemistry. He received a Ph.D. from

the University of Strasbourg.

As a postdoctoral fellow, he worked

with R. B. Woodward at Harvard on

the total synthesis of vitamin

(See pages 000 and 000.) He is a

professor of chemistry at the

Université Louis Pasteur in

Strasbourg, France, and at the

Collège de France in Paris.

B 12.

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