CHAPTER 13 – BENZENE & ITS
DERIVATIVES
AROMATIC COMPOUNDS
 Originally named because some had nice aromas.
 Aromatic compounds contain a benzene ring (C6H6).
H
H
H
H
H
H
Aliphatics – hydrocarbons not containing a benzene ring
(alkanes, alkenes, alkynes).
Aromatics are different from aliphatics because do not
behave like an unsaturated hydrocarbon (not actually 3
single bonds and 3 double bonds, more like six 1½ bonds
between carbons).
Bromine does not react with benzene (benzene more stable
than double bonded hydrocarbons).
Benzene can be represented as:
Resonance structure
H
H
H
H
H
H
H
H
H
H
H
H
Naming benzene derivatives
1. One group attached to benzene ring: name of group then
benzene.
i.e.
Cl
CH2CH3
chlorobenzene
CH2CH2CH3
I
Common Names of Benzene derivatives
CH3
NH2
O
C-OH
aniline
benzoic acid
OH
toluene
phenol
2. Two groups attached to benzene ring: use ortho, meta,
para names to identify where groups are attached to ring
in place of numbers. (ortho = 1,2; meta = 1,3; para = 1,4)
Br
Br
Br
Br
Br
Br
ortho-dibromobenzene meta-dibromobenzene
(1,2)
(1,3)
para-dibromobenzene
(1,4)
Br
CH3
Cl
Br
3. Three or more groups attached to benzene ring: use
number to identify where groups are attached.
Br
CH3
Br
O2N
Br
NO2
NO2
1,2,4-tribromobenzene
2,4,6-trinitrotoluene
(TNT)
Br
Br
Cl
4. To name the benzene ring as a group, call phenyl, not
benzyl. Use phenyl if other functional groups are present
phenyl
CH2CH3OH
2-phenyl ethanol
Polynuclear Aromatic Hydrocarbons (PAHs) – contain 2
or more benzene rings, with each ring sharing 2 carbon
atoms.
Napthalene
Benzopyrene (in cigarette smoke)
Carcinogen – a compound that causes cancer
PHENOLS
-OH attached to aromatic ring
OH
OH
Cl
Phenol
Lister (1867), discovered phenol solution kills bacteria,
used as antiseptic for surgery (no longer used on patients,
burns skin)
OH
C-OCH3
O
Methyl salicylate (a non-toxic antiseptic)(oil of wintergreen)
Chemical properties of phenols: weak acid; easily oxidized.
Phenols used in foods as an antioxidant (prevents food
from being oxidized by air).
OH
OH
(CH3)3 C
C(CH3)3
C(CH3)3
CH3
O-CH3
BHT
BHA
(butylated hydroxytoluene) (butylated hydroxyanisole)