Chapter 26
Systematic Nomenclature
26.1 Nomenclature of Hydrocarbons
26.2 Nomenclature of the Derivatives of
Hydrocarbons
26.3 Nomenclature of the Derivatives of
Aromatic Hydrocarbons
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New Way Chemistry for Hong Kong A-Level Book 3A
26.1 Nomenclature of Hydrocarbons (SB p.34)
Nomenclature: naming of compounds
The formal system of nomenclature is proposed by the
International Union of Pure and Applied Chemistry (IUPAC)
Fundamental principle of IUPAC system of nomenclature:
Each different compound should have a different name.
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26.1 Nomenclature of Hydrocarbons (SB p.35)
Straight-Chain Acyclic Hydrocarbons
1. The naming of organic compounds is based on the parent
hydrocarbon they derived from.
The number of carbon atoms in hydrocarbons is represented
by stem names.
3
Number of
carbon
atoms
Stem
name
Number of
carbon
atoms
Stem
name
1
2
3
4
5
MethEthPropButPent-
6
7
8
9
10
HexHeptOctNonDec-
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26.1 Nomenclature of Hydrocarbons (SB p.35)
2. (a) The suffix ‘ane’ is used for saturated hydrocarbons.
4
Condensed structural
formula
Name
CH4
CH3CH3
CH3CH2CH3
CH3(CH2)2CH3
CH3(CH2)3CH3
CH3(CH2)4CH3
CH3(CH2)5CH3
CH3(CH2)6CH3
CH3(CH2)7CH3
CH3(CH2)8CH3
Methane
Ethane
Propane
Butane
Pentane
Hexane
Heptane
Octane
Nonane
Decane
New Way Chemistry for Hong Kong A-Level Book 3A
26.1 Nomenclature of Hydrocarbons (SB p.36)
(b) The suffix ‘ene’ is used for unsaturated hydrocarbons
with a double bond.
e.g. CH2 = CH2
CH3CH = CH2
ethene
propene
(c) The suffix ‘yne’ is used for unsaturated hydrocarbons
with a triple bond.
e.g. CH  CH
CH3CH  CH
5
ethyne
propyne
New Way Chemistry for Hong Kong A-Level Book 3A
26.1 Nomenclature of Hydrocarbons (SB p.36)
3. The lowest possible number is assigned to the carbon atoms
of the multiple bond.
The number is written before the suffix to indicate the
position of the carbon atom of the multiple bond
e.g. CH3CH2CH = CH2
CH3C  CCH2CH3
6
but-1-ene (not but-3-ene)
pent-2-yne (not pent-3-yne)
New Way Chemistry for Hong Kong A-Level Book 3A
26.1 Nomenclature of Hydrocarbons (SB p.36)
4. If a compound contains more than one double or triple
bond, the prefixes like ‘di-’, ‘tri-’, are used to indicate its
number of occurrence. An ‘a’ is added to the corresponding
stem name.
e.g. CH3CH2CH = CHCH = CH2
hexa-1,3-diene
5. If a double or triple bond is not named in the ending of a
name, the suffix ‘-en-’ and ‘-yn-’ are used respectively in
the name.
e.g. CH2 = CHOH
7
ethenol
New Way Chemistry for Hong Kong A-Level Book 3A
26.1 Nomenclature of Hydrocarbons (SB p.36)
6. The geometric isomers of an alkene are specified by the
word of ‘cis-’ or ‘trans-’ before their names.
e.g.
8
New Way Chemistry for Hong Kong A-Level Book 3A
26.1 Nomenclature of Hydrocarbons (SB p.36)
Branched-Chain Acyclic Hydrocarbons
1. Select and name the parent hydrocarbon
(a) For saturated hydrocarbons,
Parent chain: longest possible straight chain
branched chain: all remaining
e.g,
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New Way Chemistry for Hong Kong A-Level Book 3A
26.1 Nomenclature of Hydrocarbons (SB p.37)
(b) For unsaturated hydrocarbons,
Parent chain: longest possible straight chain which
contains the maximum number of multiple bonds
(c) The parent hydrocarbon is named as described in the
naming of straight-chain acyclic hydrocarbons
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New Way Chemistry for Hong Kong A-Level Book 3A
26.1 Nomenclature of Hydrocarbons (SB p.37)
2. Name the branched chains
(a) The number of carbon atoms in a branched chain is
indicated by the stem names
(b) The suffix ‘-yl’ is added to the corresponding stem
names for branched chains containing only single bonds.
e.g. – CH3
11
methyl
– CH2CH2CH3
propyl
– CH2(CH2)2CH3
butyl
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26.1 Nomenclature of Hydrocarbons (SB p.37)
3. Numbering carbon atoms in the parent hydrocarbon
(a) For saturated hydrocarbons, the parent hydrocarbon is
numbered beginning with the end of the chain nearer the
branched chain.
e.g.
12
New Way Chemistry for Hong Kong A-Level Book 3A
26.1 Nomenclature of Hydrocarbons (SB p.37)
3. (b) For unsaturated hydrocarbons, the parent hydrocarbon is
numbered so as to include both carbon atoms of the
double or triple bond. The numbering begins with the
end of the chain nearer the double or triple bond.
e.g.
13
New Way Chemistry for Hong Kong A-Level Book 3A
26.1 Nomenclature of Hydrocarbons (SB p.38)
4. Use the numbers to designate the position of the branched chain. The
parent name is placed last, and the branched chain, preceded by the
number designating its position on the parent chain, is placed first.
e.g.
14
New Way Chemistry for Hong Kong A-Level Book 3A
26.1 Nomenclature of Hydrocarbons (SB p.38)
5. When two or more branched chains are present, a number
corresponding to its position on the parent hydrocarbon is given to
each branched chain so as to give the lowest possible numbers to
the branched chains. The branched chains are listed alphabetically
(i.e. ethyl before methyl). Multiplying prefixes such as ‘di’ and ‘tri’
are ignored when deciding the alphabetical order.
e.g.
15
New Way Chemistry for Hong Kong A-Level Book 3A
26.1 Nomenclature of Hydrocarbons (SB p.38)
6. When two branched chains are present on the same carbon
atom, use that number twice.
e.g.
16
New Way Chemistry for Hong Kong A-Level Book 3A
26.1 Nomenclature of Hydrocarbons (SB p.39)
7. When two or more branched chains are identical, indicate
this by the use of the prefixes ‘di-’, ‘tri-’, ‘tetra-’, and so on.
Commas are used to separate numbers from each other.
e.g.
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New Way Chemistry for Hong Kong A-Level Book 3A
26.1 Nomenclature of Hydrocarbons (SB p.39)
Cyclic Hydrocarbons
Simple cyclic hydrocarbons are named by adding prefix ‘cyclo-’
to the names of their corresponding acyclic counterparts.
e.g.
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New Way Chemistry for Hong Kong A-Level Book 3A
26.1 Nomenclature of Hydrocarbons (SB p.39)
Aromatic Hydrocarbons
1. Some aromatic hydrocarbons possess specific names.
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New Way Chemistry for Hong Kong A-Level Book 3A
26.1 Nomenclature of Hydrocarbons (SB p.39)
2. In substituted benzenes, the benzene ring is numbered so as to give
the lowest possible numbers to the substituents. When more than
two substituents are present and the substituents are different, they
are listed in alphabetical order.
e.g.
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New Way Chemistry for Hong Kong A-Level Book 3A
26.1 Nomenclature of Hydrocarbons (SB p.40)
Example 26-1
Give the structural formula for each of the following compounds:
(a) 2-methylbutane
(b) 2,2,3-trimethylpentane
(c) 3-ethyl-2-methylhexane
(d) 3-methylbut-1-ene
(e) 2-propylpent-1-ene
(f) 3-ethylhex-1-yne
(g) 1,2-dimethylbenzene
(h) cyclopentane
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Answer
26.1 Nomenclature of Hydrocarbons (SB p.40)
Solution:
22
(a)
(b)
(c)
(d)
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26.1 Nomenclature of Hydrocarbons (SB p.40)
Solution:
23
(e)
(f)
(g)
(h)
New Way Chemistry for Hong Kong A-Level Book 3A
26.1 Nomenclature of Hydrocarbons (SB p.41)
Check Point 26-1
Give the IUPAC name for each of the following compounds:
(a)
(b)
(a) Dimethylpropane
(c)
(d)
(b) 2,4-Dimethylhex-2-ene
(e)
(c) 3-Methylpent-1-yne
(d) 1-Methylcyclohexene
(e) Ethylbenzene
Answer
24
New Way Chemistry for Hong Kong A-Level Book 3A
26.2 Nomenclature of the Derivatives of Hydrocarbons (SB p.41)
Nomenclature of Compounds with One Type of Functional Group
Compounds with functional groups
that must be designated as prefixes
25
Group
Formula
Prefix
fluoride
chloride
bromide
iodide
ether
azo
nitro
alky or aryl
substituents
—F
— Cl
— Br
—I
— OR
—N=N—
— NO2
e.g. — CH3
fluorochlorobromoiodoalkoxy- (e.g. methoxy-)
azonitromethyl
phenyl
New Way Chemistry for Hong Kong A-Level Book 3A
26.2 Nomenclature of the Derivatives of Hydrocarbons (SB p.42)
1. The carbon chains are named and numbered in the usual
way. Numbers are assigned to functional groups in the same
way as the alkyl substituents.
e.g.
26
New Way Chemistry for Hong Kong A-Level Book 3A
26.2 Nomenclature of the Derivatives of Hydrocarbons (SB p.42)
2. When the parent chain has both alkyl groups and other
substituents, the chain is numbered from the end nearer the first
substituent, regardless of what substituents are. All the prefixes
are then arranged in alphabetical order.
e.g.
27
New Way Chemistry for Hong Kong A-Level Book 3A
26.2 Nomenclature of the Derivatives of Hydrocarbons (SB p.43)
3. When two or more substituents are identical, indicate this by
the use of the prefixes ‘di-’, ‘tri-’, ‘tetra-’, and so on.
e.g.
28
New Way Chemistry for Hong Kong A-Level Book 3A
26.2 Nomenclature of Derivatives of Hydrocarbons (SB p.43)
Compounds with functional groups that may
be designated as prefixes or suffixes
Group
General
formula
Suffix
Systematic name
Carboxylic acid
RCO2H
-oic acid
alkanoic acid
Ester
RCO2R’
-oate
alkyl alkanoate
Acyl chloride
ROCl
Amide
RCONH2
29
-oyl chloride alkanoyl chloride
-amide
alkanamide
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Structural
formula
26.2 Nomenclature of Derivatives of Hydrocarbons (SB p.43)
Compounds with functional groups that may
be designated as prefixes or suffixes
30
Group
General
formula
Suffix
Systematic name
Aldehyde
RCHO
-al
alkanal
Ketone
RCOR’
-one
alkanone
Alcohol
ROH
-ol
alkanol
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Structural
formula
26.2 Nomenclature of Derivatives of Hydrocarbons (SB p.44)
Principal functional group is the functional group expressed
as a suffix and has priority over unsaturated centres.
Parent carbon chain is chosen to include the longest possible
carbon chain and maximum number of principal functional
groups.
The carbon chain is numbered to give the principal functional
group the lower number.
The position of the principal functional group is indicated by
using this number, and the positions of other substituents are
indicated by using the numbers corresponding to their positions
along the parent carbon chain.
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New Way Chemistry for Hong Kong A-Level Book 3A
26.2 Nomenclature of Derivatives of Hydrocarbons (SB p.44)
1. Alcohols (ending ‘-ol’)
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New Way Chemistry for Hong Kong A-Level Book 3A
26.2 Nomenclature of Derivatives of Hydrocarbons (SB p.44)
2. Aldehydes (ending ‘-al’) and ketones (ending ‘-one’)
The carbon atom of the carbonyl group (i.e.
included in the parent carbon chain.
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New Way Chemistry for Hong Kong A-Level Book 3A
) is
26.2 Nomenclature of Derivatives of Hydrocarbons (SB p.45)
3. Carboxylic acids (ending ‘-oic acid’)
The carbon atom of the carboxyl group (i.e.
included in the parent carbon chain.
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New Way Chemistry for Hong Kong A-Level Book 3A
) is
26.2 Nomenclature of Derivatives of Hydrocarbons (SB p.45)
4. Acyl chlorides (ending ‘-yl chloride’)
The carbon atom of the
group is included in
the parent carbon chain.
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New Way Chemistry for Hong Kong A-Level Book 3A
26.2 Nomenclature of Derivatives of Hydrocarbons (SB p.45)
5. Amides (ending ‘-amide’)
The carbon atom of the amide group (i.e.
) is
included in the parent carbon chain. Alkyl groups on the
nitrogen atom of amides are named as substituents and the
named substituent is preceded by N- or N,N-.
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New Way Chemistry for Hong Kong A-Level Book 3A
26.2 Nomenclature of Derivatives of Hydrocarbons (SB p.45)
6. Ester (ending ‘-oate’)
The name of ester is derived from the names of the alcohol
(with the ending ‘-yl’) and the carboxylic acid (with the ending
‘-oate’) forming the ester. The portion of the name derived from
the alcohol comes first, and then the carboxylic acid.
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New Way Chemistry for Hong Kong A-Level Book 3A
26.2 Nomenclature of the Derivatives of Hydrocarbons (SB p.46)
Example 26-2
Give the structural formula for each of the following compounds:
(a) 2-methylhexane
(b) 4-methylheptan-2-ol
(c) pentan-2-one
(d) 5-methylhexanoic acid
(e) methyl 2,2-dimethylpentanoate
(f) N-ethyl-N-propylethanamide
Answer
38
New Way Chemistry for Hong Kong A-Level Book 3A
26.2 Nomenclature of the Derivatives of Hydrocarbons (SB p.46)
Solution:
39
(a)
(b)
(c)
(d)
New Way Chemistry for Hong Kong A-Level Book 3A
26.2 Nomenclature of the Derivatives of Hydrocarbons (SB p.46)
Solution:
(e)
40
(f)
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26.2 Nomenclature of the Derivatives of Hydrocarbons (SB p.46)
Check Point 26-2
Give the IUPAC name for each of the following compounds:
(a)
(c)
(b)
(a) 3,4-Dimethylpentanoic
acid
(d)
(b) Pentan-2-ol
(c) 3,4-Dimethylhexanal
(d) N,N-Dimethylpropanamide
Answer
41
New Way Chemistry for Hong Kong A-Level Book 3A
26.2 Nomenclature of Derivatives of Hydrocarbons (SB p.47)
Nomenclature of Compounds with More than
One Type of Functional Group
1. Only one of the functional groups can be designated as the
ending of the name. This is the principal functional group.
The priority of choosing principal functional group in
decreasing order is listed in the following table.
The group that is highest in the list precedes all other groups
and become the principal functional group in the compound to
be named.
42
New Way Chemistry for Hong Kong A-Level Book 3A
26.2 Nomenclature of Derivatives of Hydrocarbons (SB p.47)
Group
43
Formula
Prefix
Suffix
Carboxylic acid
carboxy
-oic acid
Sulphonic acid
sulpho
-sulphonic acid
Ester
—
-oate
Acyl halide
—
-oyl halide
Amide
—
-amide
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26.2 Nomenclature of Derivatives of Hydrocarbons (SB p.47)
Group
44
Formula
Prefix
Suffix
Nitrile
cyano
-nitrile
Aldehyde
oxo
-al
Ketone
oxo
-one
Alcohol
hydroxy -ol
Amine
amino
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-amine
26.2 Nomenclature of Derivatives of Hydrocarbons (SB p.48)
2. The principal functional group has priority in the selection of
the longest possible carbon chain and the choice of lowest
number.
Other groups are designated as prefixes and listed in
alphabetical order.
45
New Way Chemistry for Hong Kong A-Level Book 3A
26.2 Nomenclature of Derivatives of Hydrocarbons (SB p.48)
Example 1:
4-chloro-4-methylpentanal
Principal functional group:
Parent chain:
46
New Way Chemistry for Hong Kong A-Level Book 3A
26.2 Nomenclature of Derivatives of Hydrocarbons (SB p.48)
Example 2:
2-bromo-3-methylbut-2-enoic acid
Principal functional group:
Parent chain:
47
New Way Chemistry for Hong Kong A-Level Book 3A
26.2 Nomenclature of Derivatives of Hydrocarbons (SB p.49)
Example 3:
3-chloro-2-iodobutanamide
Principal functional group:
Parent chain:
48
New Way Chemistry for Hong Kong A-Level Book 3A
26.2 Nomenclature of Derivatives of Hydrocarbons (SB p.49)
Example 4:
3,4-dichloro-5-hydroxy-4-methylpentan-2-one
Principal functional group:
Parent chain:
49
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26.2 Nomenclature of Derivatives of Hydrocarbons (SB p.50)
Example 5:
4-amino-2-phenylhexanal
Principal functional group:
Parent chain:
50
New Way Chemistry for Hong Kong A-Level Book 3A
26.2 Nomenclature of the Derivatives of Hydrocarbons (SB p.51)
Example 26-3
Solution:
Give the structural formula for each of the following compounds:
(a)
(a) 3-oxobutanoic acid
(b)
(b) 5-hydroxypentanal
(c) 2-hydroxy-4-oxohexanal
(d) 1,8-dihydroxyoctan-3-one
(c)
51
(d)
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Answer
26.2 Nomenclature of the Derivatives of Hydrocarbons (SB p.51)
Example 26-4
A student has given the wrong names for the following organic
compounds. Given the structural formulae and the correct names
Solution:
for these compounds.
(a)
(a) 3-hydroxy-3-ethylbutanoic acid
(b) 2-chloro-3-cyano-1-methylpropane
Answer
(c) propoxyethane
3-Hydroxy-3-methylpentanoic acid
52
New Way Chemistry for Hong Kong A-Level Book 3A
26.2 Nomenclature of the Derivatives of Hydrocarbons (SB p.52)
Solution:
(b)
3-Chloropentanenitrile
(c)
Ethoxypropane
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New Way Chemistry for Hong Kong A-Level Book 3A
26.2 Nomenclature of the Derivatives of Hydrocarbons (SB p.52)
Check Point 26-3
Give the IUPAC name for each of the following compounds:
(a)
(b)
(a) 3-Chlorobutanone
(c)
(d)
(b) 1-Ethoxyethanol
(c) 2-Amino-3-hydroxypentanoic acid
(d) 4-Hydroxy-2-methylpentanamide
Answer
54
New Way Chemistry for Hong Kong A-Level Book 3A
26.3 Nomenclature of Derivatives of Aromatic Hydrocarbons (SB p.53)
Monosubstituted Aromatic Hydrocarbons
1. Some monosubstituted aromatic hydrocarbons can be named by
adding the name of the substituents as prefixes to the name of
the aromatic hydrocarbon.
e.g.
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New Way Chemistry for Hong Kong A-Level Book 3A
26.3 Nomenclature of Derivatives of Aromatic Hydrocarbons (SB p.53)
2. For other monosubstituted aromatic hydrocarbons, the substituent
and the benzene ring taken together may form a new parent name.
e.g.
56
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26.3 Nomenclature of Derivatives of Aromatic Hydrocarbons (SB p.53)
57
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26.3 Nomenclature of Derivatives of Aromatic Hydrocarbons (SB p.54)
Polysubstituted Aromatic Hydrocarbons
1. When two or more substituents are identical, indicate this by the use
of the prefixes ‘di-’, ‘tri-’, ‘tetra-’ and so on. The benzene ring is
numbered so as to give the lowest possible numbers to the
substituents.
e.g.
58
New Way Chemistry for Hong Kong A-Level Book 3A
26.3 Nomenclature of Derivatives of Aromatic Hydrocarbons (SB p.54)
2. When the substituents are different, they are listed in
alphabetical order.
e.g.
59
New Way Chemistry for Hong Kong A-Level Book 3A
26.3 Nomenclature of Derivatives of Aromatic Hydrocarbons (SB p.54)
3. When a substituent is one that when taken together with the
benzene ring to give a new parent name, that substituent is
assumed to be in position 1 and the new parent name is used.
e.g.
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New Way Chemistry for Hong Kong A-Level Book 3A
26.3 Nomenclature of the Derivatives of Aromatic Hydrocarbons (SB p.55)
Example 26-5
Solution:
Give the structural formula for each of the following compounds:
(a)
(a) 1,4-dichlorobenzene
(b)
(b) 3-nitrobenzoic acid
(c) 4-bromotoluene
Answer
(d) 3,5-dinitrophenol
(c)
61
(d)
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26.3 Nomenclature of the Derivatives of Aromatic Hydrocarbons (SB p.51)
Check Point 26-4
Give the IUPAC name for each of the following compounds:
(a)
(b)
(a) 2-Bromo-1,4-dichlorobenzene
(c)
(d)
(b) 5-Bromo-2-chlorobenzoic acid
(c) 2,4-Difluorobenzenesulphonic acid
(d) 4-Hydroxybenzoic acid
Answer
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The END
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