CHEMISTRY 122 - Seattle Central College

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CHEMISTRY 122
HW CH#4 AROMATIC COMPOUNDS
4, 6, 8, 10, 14, 16, 18, 20, 22, 24, 26, 38, 40
4-4
An aromatic compound is one that contains one or more benzene rings.
4-6
Aromatic rings have double bonds in the contributing structures we normally use
to represent them. They are unsaturated because they have fewer hydrogen atoms than a
cycloalkane with the same number of carbons.
4-8
(a) An alkene of six carbons has the molecular formula C6H12 and contains one
carbon-carbon double bond. Three examples are:
1-Hexene
trans-3-Hexene
cis-3-Hexene
(b) A cycloalkene of six carbons has the molecular formula C6H10 and contains
one ring and one carbon-carbon double bond. Three examples are:
Cyclohexene
4-Methylcyclopentene
1-Methylcyclopentene
(c) An alkyne of six carbons has the molecular formula C6H10 and contains one
carbon-carbon triple bond. Three examples are:
1-Hexyne
2-Hexyne
4-Methyl-2-pentyne
(d) An aromatic hydrocarbon of eight carbons has the molecular formula C8H10
and contains one benzene ring. Three examples are:
Ethylbenzene
1,3-Dimethylbenzene
(m-Xylene)
1,4-Dimethylbenzene
(p-Xylene)
4-10
Benzene consists of carbons, each surrounded by three regions of electron
density, which gives 120° for all bond angles. Bond angles of 120° in benzene
can be maintained only if the molecule is planar. Cyclohexane, on the other hand,
consists of carbons, each surrounded by four regions of electron density, which
gives 109.5° for all bond angles. Angles of 109.5° in cyclohexane can be
maintained only if the molecule is nonplanar.
4-14
(a)
(b)
(c)
(d)
(e)
(f)
(g)
(h)
1-Chloro-4-nitrobenzene (p-chloronitrobenzene)
2-Bromotoluene (o-bromotoluene)
1-Chloro-3-phenylpropane
2-Bromo-2-phenylbutane
2-Nitroaniline (o-nitroaniline)
2-Phenylphenol (o-phenylphenol)
trans-1,2-Diphenylethene (trans-1,2-diphenylethylene)
2,4-Dichlorotoluene
4-16
Polynuclear means that each contains two or more rings bonded in such a way
that each ring shares two adjacent atoms with another ring. Aromatic means that
each ring is six-membered and has three carbon-carbon double bonds; that is,
each has an aromatic sextet. Hydrocarbon means that these compounds consist of
only carbon and hydrogen.
4-18
(a), (b), (c), (d): True
4-20
Br
Br
Br
Cl
13.20
Cl
1-Bromo-2chlorobenzene
(o-Chlorobromobenzene)
1-Bromo-3chlorobenzene
(m-Chlorobromobenzene)
Cl
1-Bromo-4chlorobenzene
(p-Chlorobromobenzene)
4-22
(a) Nitration using HNO3/H2SO4
(b) Bromination using Br2/FeCl3
(c) Nitration using HNO3/H2SO4 followed by catalytic reduction using H2/Ni
4-24
The two sulfonated naphthalenes are:
SO3H
SO3H
1-Naphthalenesulfonic acid
2-Naphthalenesulfonic acid
4-26
Phenol is a sufficiently strong acid that it reacts with strong bases such as sodium
hydroxide to form sodium phenoxide, a water-soluble salt. Cyclohexanol has no
comparable acidity and does not react with sodium hydroxide
4-38
A substance that is biodegradable can chemically breakdown into
environmentally friendly products, usually by bacteria or other biological means.
4-40
Iodine is an element that is found primarily in seawater and, therefore, seafood is
a rich source of it. Individuals in inland areas where seafood is only a limited part
of the diet are the most susceptible to developing goiter.
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