new way chemistry for hong kong a-level book 3a1 systematic nomenclature 26.1nomenclature of...

New Way Chemistry for Hong Kong A-Level Book 3A

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Systematic Nomenclature

26.126.1 Nomenclature of HydrocarbonsNomenclature of Hydrocarbons

26.226.2 Nomenclature of the Derivatives of Nomenclature of the Derivatives of HydrocarbonsHydrocarbons

26.326.3 Nomenclature of the Derivatives of Nomenclature of the Derivatives of Aromatic HydrocarbonsAromatic Hydrocarbons

Chapter 26Chapter 26


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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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Number of carbon atoms

Stem name

Number of carbon atoms

Stem name

1

2

3

4

5

Meth-

Eth-

Prop-

But-

Pent-

6

7

8

9

10

Hex-

Hept-

Oct-

Non-

Dec-

Straight-Chain Acyclic HydrocarbonsStraight-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.


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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

2. (a) The suffix ‘ane’ is used for saturated hydrocarbons.


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(b) The suffix ‘ene’ is used for unsaturated hydrocarbons with a double bond.

e.g. CH2 = CH2 ethene

CH3CH = CH2 propene

(c) The suffix ‘yne’ is used for unsaturated hydrocarbons with a triple bond.

e.g. CH CH ethyne

CH3CH CH propyne


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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 but-1-ene (not but-3-ene)

CH3C CCH2CH3 pent-2-yne (not pent-3-yne)


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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 ethenol


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6. The geometric isomers of an alkene are specified by the word of ‘cis-’ or ‘trans-’ before their names.e.g.


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Branched-Chain Acyclic HydrocarbonsBranched-Chain Acyclic Hydrocarbons

1. Select and name the parent hydrocarbon(a) For saturated hydrocarbons,

Parent chain: longest possible straight chainbranched chain: all remaining e.g,


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(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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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 methyl

– CH2CH2CH3 propyl

– CH2(CH2)2CH3 butyl


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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.


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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.


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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.


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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.


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6. When two branched chains are present on the same carbon atom, use that number twice.e.g.


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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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Cyclic HydrocarbonsCyclic Hydrocarbons

Simple cyclic hydrocarbons are named by adding prefix ‘cyclo-’ to the names of their corresponding acyclic counterparts.e.g.


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Aromatic HydrocarbonsAromatic Hydrocarbons

1. Some aromatic hydrocarbons possess specific names.


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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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Example 26-1Example 26-1Give 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


Answer


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Solution:

(a) (b)

(c) (d)



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Solution:

(e) (f)

(g) (h)



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Check Point 26-1 Check Point 26-1

Give the IUPAC name for each of the following compounds:

(a) (b)

(c) (d) (e)

Answer


(a) Dimethylpropane

(b) 2,4-Dimethylhex-2-ene

(c) 3-Methylpent-1-yne

(d) 1-Methylcyclohexene

(e) Ethylbenzene


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26.2 Nomenclature of the Derivatives of Hydrocarbons (SB p.41)

Nomenclature of Compounds with One Type of Functional GroupNomenclature of Compounds with One Type of Functional Group

Compounds with functional groups that must be designated as prefixes

fluoro-

chloro-

bromo-

iodo-

alkoxy- (e.g. methoxy-)

azo-

nitro-

methylphenyl

— F

— Cl

— Br

— I

— OR

— N = N —

— NO2

e.g. — CH3

fluoride

chloride

bromide

iodide

ether

azo

nitro

alky or aryl substituents

PrefixFormulaGroup


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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.



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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.



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3. When two or more substituents are identical, indicate this by the use of the prefixes ‘di-’, ‘tri-’, ‘tetra-’, and so on.e.g.



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26.2 Nomenclature of Derivatives of Hydrocarbons (SB p.43)

Compounds with functional groups that may be designated as prefixes or suffixes

alkanamide-amideRCONH2Amide

alkanoyl chloride-oyl chlorideROClAcyl chloride

alkyl alkanoate-oateRCO2R’Ester

alkanoic acid-oic acidRCO2HCarboxylic acid

Structural formula

Systematic nameSuffixGeneral formula

Group


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alkanal-alRCHOAldehyde

alkanol-olROHAlcohol

alkanone-oneRCOR’Ketone

Structural formula

Systematic nameSuffixGeneral formula

Group

Compounds with functional groups that may be designated as prefixes or suffixes


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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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1. Alcohols (ending ‘-ol’)


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2. Aldehydes (ending ‘-al’) and ketones (ending ‘-one’)

The carbon atom of the carbonyl group (i.e. ) is

included in the parent carbon chain.


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3. Carboxylic acids (ending ‘-oic acid’)

The carbon atom of the carboxyl group (i.e. ) is

included in the parent carbon chain.


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4. Acyl chlorides (ending ‘-yl chloride’)

The carbon atom of the group is included in the pare

nt carbon chain.


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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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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 th

e alcohol comes first, and then the carboxylic acid.


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(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-propylethanamideAnswer



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Solution:

(a) (b)

(c) (d)



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Solution:

(e) (f)



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(a) (b)

(c) (d)

Answer


(a) 3,4-Dimethylpentanoic aci

d

(b) Pentan-2-ol

(c) 3,4-Dimethylhexanal

(d) N,N-Dimethylpropanamide


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Nomenclature of Compounds with More than One Type of Functional Group

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.


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Group 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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Group Formula Prefix Suffix

Nitrile cyano -nitrile

Aldehyde oxo -al

Ketone oxo -one

Alcohol hydroxy -ol

Amine amino -amine


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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.


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Example 1:

Principal functional group:

Parent chain:

4-chloro-4-methylpentanal


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Example 2:


Parent chain:

2-bromo-3-methylbut-2-enoic acid


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Example 3:


Parent chain:

3-chloro-2-iodobutanamide


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Example 4:


Parent chain:

3,4-dichloro-5-hydroxy-4-methylpentan-2-one


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Example 5:


Parent chain:

4-amino-2-phenylhexanal


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(a) 3-oxobutanoic acid

(b) 5-hydroxypentanal

(c) 2-hydroxy-4-oxohexanal

(d) 1,8-dihydroxyoctan-3-one

Answer


Solution:

(a) (b)

(c) (d)


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Example 26-4Example 26-4A student has given the wrong names for the following organic compounds. Given the structural formulae and the correct names for these compounds.

(a) 3-hydroxy-3-ethylbutanoic acid

(b) 2-chloro-3-cyano-1-methylpropane

(c) propoxyethaneAnswer


Solution:

(a)

3-Hydroxy-3-methylpentanoic acid


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Solution:

(b)

3-Chloropentanenitrile

(c)

Ethoxypropane


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(a) (b)

(c) (d)

Answer


(a) 3-Chlorobutanone

(b) 1-Ethoxyethanol

(c) 2-Amino-3-hydroxypentanoic acid

(d) 4-Hydroxy-2-methylpentanamide


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26.3 Nomenclature of Derivatives of Aromatic Hydrocarbons (SB p.53)

Monosubstituted Aromatic HydrocarbonsMonosubstituted 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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2. For other monosubstituted aromatic hydrocarbons, the substituent and the benzene ring taken together may form a new parent name.e.g.


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Polysubstituted Aromatic HydrocarbonsPolysubstituted 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.


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2. When the substituents are different, they are listed in alphabetical order.e.g.


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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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(a) 1,4-dichlorobenzene

(b) 3-nitrobenzoic acid

(c) 4-bromotoluene

(d) 3,5-dinitrophenol

Answer

26.3 Nomenclature of the Derivatives of Aromatic Hydrocarbons (SB p.55)

Solution:

(a) (b)

(c) (d)


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26.3 Nomenclature of the Derivatives of Aromatic Hydrocarbons (SB p.51)



(a) (b)

(c) (d)

Answer

(a) 2-Bromo-1,4-dichlorobenzene

(b) 5-Bromo-2-chlorobenzoic acid

(c) 2,4-Difluorobenzenesulphonic acid

(d) 4-Hydroxybenzoic acid


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