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:
(b)A cycloalkene of six carbons has the molecular formula C6H10 and contains one ring and one carbon-carbon double bond. Three examples are:
(c)An alkyne of six carbons has the molecular formula C6H10 and contains one carbon-carbon triple bond. Three examples are:
(d)An aromatic hydrocarbon of eight carbons has the molecular formula C8H10 and contains one benzene ring. Three examples are:
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)1-Chloro-4-nitrobenzene (p-chloronitrobenzene)
(b)2-Bromotoluene (o-bromotoluene)
(c)1-Chloro-3-phenylpropane
(d)2-Bromo-2-phenylbutane
(e)2-Nitroaniline (o-nitroaniline)
(f)2-Phenylphenol (o-phenylphenol)
(g)trans-1,2-Diphenylethene (trans-1,2-diphenylethylene)
(h)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
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:
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.