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New Way Chemistry for Hong Kong A-Level Book 3A
1
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
New Way Chemistry for Hong Kong A-Level Book 3A
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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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26.1 Nomenclature of Hydrocarbons (SB p.35)
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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26.1 Nomenclature of Hydrocarbons (SB p.35)
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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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 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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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 but-1-ene (not but-3-ene)
CH3C CCH2CH3 pent-2-yne (not pent-3-yne)
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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 ethenol
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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.
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26.1 Nomenclature of Hydrocarbons (SB p.36)
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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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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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 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.
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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.
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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.
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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.
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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.
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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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26.1 Nomenclature of Hydrocarbons (SB p.39)
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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26.1 Nomenclature of Hydrocarbons (SB p.39)
Aromatic HydrocarbonsAromatic Hydrocarbons
1. Some aromatic hydrocarbons possess specific names.
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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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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
26.1 Nomenclature of Hydrocarbons (SB p.40)
Answer
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Solution:
(a) (b)
(c) (d)
26.1 Nomenclature of Hydrocarbons (SB p.40)
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Solution:
(e) (f)
(g) (h)
26.1 Nomenclature of Hydrocarbons (SB p.40)
New Way Chemistry for Hong Kong A-Level Book 3A
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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
26.1 Nomenclature of Hydrocarbons (SB p.41)
(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.
26.2 Nomenclature of the Derivatives of Hydrocarbons (SB p.42)
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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.
26.2 Nomenclature of the Derivatives of Hydrocarbons (SB p.42)
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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.
26.2 Nomenclature of the Derivatives of Hydrocarbons (SB p.43)
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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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26.2 Nomenclature of Derivatives of Hydrocarbons (SB p.43)
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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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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26.2 Nomenclature of Derivatives of Hydrocarbons (SB p.44)
1. Alcohols (ending ‘-ol’)
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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. ) is
included in the parent carbon chain.
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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. ) is
included in the parent carbon chain.
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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 pare
nt carbon chain.
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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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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 th
e alcohol comes first, and then the carboxylic acid.
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Example 26-2Example 26-2Give 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-propylethanamideAnswer
26.2 Nomenclature of the Derivatives of Hydrocarbons (SB p.46)
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Solution:
(a) (b)
(c) (d)
26.2 Nomenclature of the Derivatives of Hydrocarbons (SB p.46)
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Solution:
(e) (f)
26.2 Nomenclature of the Derivatives of Hydrocarbons (SB p.46)
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Check Point 26-2 Check Point 26-2
Give the IUPAC name for each of the following compounds:
(a) (b)
(c) (d)
Answer
26.2 Nomenclature of the Derivatives of Hydrocarbons (SB p.46)
(a) 3,4-Dimethylpentanoic aci
d
(b) Pentan-2-ol
(c) 3,4-Dimethylhexanal
(d) N,N-Dimethylpropanamide
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26.2 Nomenclature of Derivatives of Hydrocarbons (SB p.47)
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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26.2 Nomenclature of Derivatives of Hydrocarbons (SB p.47)
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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26.2 Nomenclature of Derivatives of Hydrocarbons (SB p.47)
Group Formula Prefix Suffix
Nitrile cyano -nitrile
Aldehyde oxo -al
Ketone oxo -one
Alcohol hydroxy -ol
Amine amino -amine
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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.
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26.2 Nomenclature of Derivatives of Hydrocarbons (SB p.48)
Example 1:
Principal functional group:
Parent chain:
4-chloro-4-methylpentanal
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26.2 Nomenclature of Derivatives of Hydrocarbons (SB p.48)
Example 2:
Principal functional group:
Parent chain:
2-bromo-3-methylbut-2-enoic acid
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26.2 Nomenclature of Derivatives of Hydrocarbons (SB p.49)
Example 3:
Principal functional group:
Parent chain:
3-chloro-2-iodobutanamide
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26.2 Nomenclature of Derivatives of Hydrocarbons (SB p.49)
Example 4:
Principal functional group:
Parent chain:
3,4-dichloro-5-hydroxy-4-methylpentan-2-one
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26.2 Nomenclature of Derivatives of Hydrocarbons (SB p.50)
Example 5:
Principal functional group:
Parent chain:
4-amino-2-phenylhexanal
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Example 26-3Example 26-3Give the structural formula for each of the following compounds:
(a) 3-oxobutanoic acid
(b) 5-hydroxypentanal
(c) 2-hydroxy-4-oxohexanal
(d) 1,8-dihydroxyoctan-3-one
Answer
26.2 Nomenclature of the Derivatives of Hydrocarbons (SB p.51)
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
26.2 Nomenclature of the Derivatives of Hydrocarbons (SB p.51)
Solution:
(a)
3-Hydroxy-3-methylpentanoic acid
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26.2 Nomenclature of the Derivatives of Hydrocarbons (SB p.52)
Solution:
(b)
3-Chloropentanenitrile
(c)
Ethoxypropane
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Check Point 26-3 Check Point 26-3
Give the IUPAC name for each of the following compounds:
(a) (b)
(c) (d)
Answer
26.2 Nomenclature of the Derivatives of Hydrocarbons (SB p.52)
(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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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.
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26.3 Nomenclature of Derivatives of Aromatic Hydrocarbons (SB p.53)
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26.3 Nomenclature of Derivatives of Aromatic Hydrocarbons (SB p.54)
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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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.
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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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Example 26-5Example 26-5Give the structural formula for each of the following compounds:
(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)
Check Point 26-4 Check Point 26-4
Give the IUPAC name for each of the following compounds:
(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