Vollhardt  Capítulo 15 (Benzenos e Aromaticidade)

Vollhardt Capítulo 15 (Benzenos e Aromaticidade)


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the NMR spectrum described?
A B
66. Explain the following reaction and the indicated stereochemical result mechanistically.
C
\ufffd H2C
CH3
HOCH2
H
CH3
H
C
(
(
GD
O
C C
1. AlCl3
2. H\ufffd, H2O
H \u221e
67. Metal-substituted benzenes have a long history of use in medicine. Before antibiotics were dis-
covered, phenylarsenic derivatives were the only treatment for a number of diseases. Phenylmer-
cury compounds continue to be used as fungicides and antimicrobial agents to the present day. 
On the basis of the general principles explained in this chapter and your knowledge of the 
 characteristics of compounds of Hg21 (see Section 12-7), propose a sensible synthesis of phenyl-
mercury acetate (shown in the margin).
Team Problem
68. As a team, discuss the following complementary experimental results as they pertain to the 
mechanism of electrophilic aromatic substitution.
 (a) A solution of HCl and benzene is colorless and does not conduct electricity, whereas a solu-
tion of HCl and AlCl3 and benzene is colored and does conduct electricity.
 (b) The following are 13C NMR chemical shifts for the species below (see also Exercise 15-24):
1
2
4
3 5
H
H
\ufffd
6
Z
Z
yy
yy
y y
 
Cl and C5: 186.6 ppm
C3: 178.1 ppm
C2 and C4: 136.9 ppm
C6: 52.2 ppm
1,6-Methano[10]annulene
H H
1,6-Methano[10]annulene
H H
HgOCCH3
Phenylmercury acetate
O
B
HgOCCH3
Phenylmercury acetate
O
B
 C h a p t e r 1 5 729
(c) The relative rates of chlorination of the following compounds are as shown.
Compound Relative Rate
Benzene 0.0005
Methylbenzene 0.157
1,4-Dimethylbenzene 1.00
1,2-Dimethylbenzene 2.1
1,2,4-Trimethylbenzene 200
1,2,3-Trimethylbenzene 340
1,2,3,4-Tetramethylbenzene 2000
1,2,3,5-Tetramethylbenzene 240,000
Pentamethylbenzene 360,000
 (d) When 1,3,5-trimethylbenzene is treated with fl uoroethane and one equivalent of BF3 at 
280 8C, an isolable solid salt with a melting point of 215 8C is produced. Heating the salt results 
in 1-ethyl-2,4,6-trimethylbenzene.
Preprofessional Problems
69. o-Iodoaniline is the common name of which of the following compounds?
(a) 
I
NH2
 
(b) 
CH3
I
CH3 
(c) 
NH2
I 
(d) 
NH2
I
70. The species that is not aromatic according to Hückel\u2019s rule is
(a) 
 
(b) 
\ufffd
\ufffd
 
(c) 
\ufffd 
(d) 
\ufffd
71. When compound A (shown in the margin) is treated with dilute mineral acid, an isomerization 
takes place. Which of the following compounds is the new isomer formed?
(a) 
CH3
CH2CH2CH3 
(b) 
CH2CH3
CH2CH3
(c) 
CH3
CH2CH3
CH3
 
(d) 
CH2CH3
CH2CH3
CHCH3
CHCH3
A
CHCH3
CHCH3
A
P r o b l e m s
730 C h a p t e r 1 5 B e n z e n e a n d A r o m a t i c i t y
72. Which set of reagents will best carry out the conversion shown?
Br
(a) HBr, peroxides; (b) Br2, FeBr3; (c) Br2 in CCl4; (d) KBr.
73. One of the compounds shown here contains carbon \u2013 carbon bonds that are 1.39Å long. 
Which one?
(a) (b) (c) 
CH3
CH3 (d) 
CH3
 (e) CCH3CCH3 q 
	Chapter 15: BENZENE AND AROMATICITY
	15-1: Naming the Benzenes
	15-2: Structure and Resonance Energy of Benzene: A First Look at Aromaticity
	15-3: Pi Molecular Orbitals of Benzene
	15-4: Spectral Characteristics of the Benzene Ring
	15-5: Polycyclic Aromatic Hydrocarbonsnull
	Chemical Highlight 15-1: The Allotropes of Carbon: Graphite, Diamond, and Fullerenes
	15-6: Other Cyclic Polyenes: Hückel\u2019s Rule
	Chemical Highlight 15-2: Juxtaposing Aromatic and Antiaromatic Rings in Fused Hydrocarbons
	15-7: Hückel\u2019s Rule and Charged Molecules
	15-8: Synthesis of Benzene Derivatives: Electrophilic Aromatic Substitution
	15-9: Halogenation of Benzene: The Need for a Catalystnull
	15-10: Nitration and Sulfonation of Benzene
	15-11: Friedel-Crafts Alkylationnull
	15-12: Limitations of Friedel-Crafts Alkylations
	15-13: Friedel-Crafts Acylation (Alkanoylation)
	Chapter Integration Problems
	New Reactions
	Important Concepts
	Problems
	Chapter 18: ENOLS, ENOLATES, AND THE ALDOL CONDENSATION