Organic Chemistry

296 CHAPTER 7 Electron Delocalization and Resonance• More About Molecular Orbital Theory

23. Which resonance contributor makes the greater contribution to the resonance hybrid?

a. or

b. c.

24. a. Which oxygen atom has the greater electron density?

b. Which compound has the greater electron density on its nitrogen atom?

c. Which compound has the greater electron density on its oxygen atom?

25. Which can lose a proton more readily, a methyl group bonded to cyclohexane or a methyl group bonded to benzene?


26. The triphenylmethyl cation is so stable that a salt such as triphenylmethyl chloride can be isolated and stored. Why is this
    carbocation so stable?


27. Draw the contributing resonance structures for the following anion, and rank them in order of decreasing stability:


28. Rank the following compounds in order of decreasing acidity:


29. Which species is more stable?

a. d.

b. e.

c. f. or

O

O

N−

O

or N−

O O

CH 3 CHCH 2 CCH 3 CH 3 CH 2 CHCCH 3

−−

or

O

CH 3 CCH

CH 3

−

CH 2

CH 3 CCH

CH 3

−

or

O O O O

CH 3 CCHCH 2 CH CH 3 CCHCCH 3

−−

or

NH 2 NH

or CH 3 CHCH 3 CH 3 CNH 2

O

CH 3 CH 2 O− CH 3 CO−

CCH

O

CH 3 CH 2 O CN

−

C

Cl−

triphenylmethyl chloride

+

CH 3 CH 3

NHCCH 3

O

NHCCH 3

O

or

N

H

or

N

H

CH 3 COCH 3

O

O

or

O−

−

CH 3

or

+

CH 3

+

CH 3 CH“CHC

+

CH 3 C H 2

+

HCH“CH 2

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