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Systematic Nomenclature

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1 Systematic Nomenclature
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

2 Nomenclature: naming of compounds
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.

3 Straight-Chain Acyclic Hydrocarbons
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. 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-

4 Condensed structural formula
26.1 Nomenclature of Hydrocarbons (SB p.35) 2. (a) The suffix ‘ane’ is used for saturated hydrocarbons. 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

5 e.g. CH2 = CH2 ethene CH3CH = CH2 propene
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

6 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)

7 e.g. CH3CH2CH = CHCH = CH2 hexa-1,3-diene
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

8 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.

9 Branched-Chain Acyclic Hydrocarbons
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,

10 (b) For unsaturated hydrocarbons,
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

11 e.g. – CH3 methyl – CH2CH2CH3 propyl – CH2(CH2)2CH3 butyl
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

12 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.

13 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.

14 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.

15 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.

16 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.

17 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.

18 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.

19 Aromatic Hydrocarbons
26.1 Nomenclature of Hydrocarbons (SB p.39) Aromatic Hydrocarbons 1. Some aromatic hydrocarbons possess specific names.

20 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.

21 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 Answer

22 26.1 Nomenclature of Hydrocarbons (SB p.40)
Solution: (a) (b) (c) (d)

23 26.1 Nomenclature of Hydrocarbons (SB p.40)
Solution: (e) (f) (g) (h)

24 26.1 Nomenclature of Hydrocarbons (SB p.41)
Check Point 26-1 Give the IUPAC name for each of the following compounds: (a) (b) (c) (d) (e) (a) Dimethylpropane (b) 2,4-Dimethylhex-2-ene (c) 3-Methylpent-1-yne (d) 1-Methylcyclohexene (e) Ethylbenzene Answer

25 Nomenclature of Compounds with One Type of Functional Group
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 fluoro- chloro- bromo- iodo- alkoxy- (e.g. methoxy-) azo- nitro- methyl phenyl — F — Cl — Br — I — OR — N = N — — NO2 e.g. — CH3 fluoride chloride bromide iodide ether azo nitro alky or aryl substituents Prefix Formula Group

26 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.

27 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.

28 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.

29 26.2 Nomenclature of Derivatives of Hydrocarbons (SB p.43)
Compounds with functional groups that may be designated as prefixes or suffixes alkanamide -amide RCONH2 Amide alkanoyl chloride -oyl chloride ROCl Acyl chloride alkyl alkanoate -oate RCO2R’ Ester alkanoic acid -oic acid RCO2H Carboxylic acid Structural formula Systematic name Suffix General formula Group

30 26.2 Nomenclature of Derivatives of Hydrocarbons (SB p.43)
Compounds with functional groups that may be designated as prefixes or suffixes alkanal -al RCHO Aldehyde alkanol -ol ROH Alcohol alkanone -one RCOR’ Ketone Structural formula Systematic name Suffix General formula Group

31 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.

32 1. Alcohols (ending ‘-ol’)
26.2 Nomenclature of Derivatives of Hydrocarbons (SB p.44) 1. Alcohols (ending ‘-ol’)

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

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

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

36 5. Amides (ending ‘-amide’)
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-.

37 6. Ester (ending ‘-oate’)
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.

38 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

39 Solution: (a) (b) (c) (d)
26.2 Nomenclature of the Derivatives of Hydrocarbons (SB p.46) Solution: (a) (b) (c) (d)

40 26.2 Nomenclature of the Derivatives of Hydrocarbons (SB p.46)
Solution: (e) (f)

41 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) (b) (c) (d) (a) 3,4-Dimethylpentanoic acid (b) Pentan-2-ol (c) 3,4-Dimethylhexanal (d) N,N-Dimethylpropanamide Answer

42 Nomenclature of Compounds with More than One Type of Functional Group
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.

43 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

44 26.2 Nomenclature of Derivatives of Hydrocarbons (SB p.47)
Group Formula Prefix Suffix Nitrile cyano -nitrile Aldehyde oxo -al Ketone -one Alcohol hydroxy -ol Amine amino -amine

45 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.

46 4-chloro-4-methylpentanal
26.2 Nomenclature of Derivatives of Hydrocarbons (SB p.48) Example 1: 4-chloro-4-methylpentanal Principal functional group: Parent chain:

47 2-bromo-3-methylbut-2-enoic acid
26.2 Nomenclature of Derivatives of Hydrocarbons (SB p.48) Example 2: 2-bromo-3-methylbut-2-enoic acid Principal functional group: Parent chain:

48 3-chloro-2-iodobutanamide
26.2 Nomenclature of Derivatives of Hydrocarbons (SB p.49) Example 3: 3-chloro-2-iodobutanamide Principal functional group: Parent chain:

49 3,4-dichloro-5-hydroxy-4-methylpentan-2-one
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:

50 4-amino-2-phenylhexanal
26.2 Nomenclature of Derivatives of Hydrocarbons (SB p.50) Example 5: 4-amino-2-phenylhexanal Principal functional group: Parent chain:

51 26.2 Nomenclature of the Derivatives of Hydrocarbons (SB p.51)
Example 26-3 Give 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 Solution: (a) (b) (c) (d) Answer

52 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 for these compounds. (a) 3-hydroxy-3-ethylbutanoic acid (b) 2-chloro-3-cyano-1-methylpropane (c) propoxyethane Solution: (a) 3-Hydroxy-3-methylpentanoic acid Answer

53 Solution: (b) 3-Chloropentanenitrile (c) Ethoxypropane
26.2 Nomenclature of the Derivatives of Hydrocarbons (SB p.52) Solution: (b) 3-Chloropentanenitrile (c) Ethoxypropane

54 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) (c) (d) (a) 3-Chlorobutanone (b) 1-Ethoxyethanol (c) 2-Amino-3-hydroxypentanoic acid (d) 4-Hydroxy-2-methylpentanamide Answer

55 Monosubstituted Aromatic Hydrocarbons
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.

56 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.

57 26.3 Nomenclature of Derivatives of Aromatic Hydrocarbons (SB p.53)

58 Polysubstituted Aromatic Hydrocarbons
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.

59 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.

60 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.

61 26. 3 Nomenclature of the Derivatives of Aromatic Hydrocarbons (SB p
Example 26-5 Give the structural formula for each of the following compounds: (a) 1,4-dichlorobenzene (b) 3-nitrobenzoic acid (c) 4-bromotoluene (d) 3,5-dinitrophenol Solution: (a) (b) (c) (d) Answer

62 26. 3 Nomenclature of the Derivatives of Aromatic Hydrocarbons (SB p
Check Point 26-4 Give the IUPAC name for each of the following compounds: (a) (b) (c) (d) (a) 2-Bromo-1,4-dichlorobenzene (b) 5-Bromo-2-chlorobenzoic acid (c) 2,4-Difluorobenzenesulphonic acid (d) 4-Hydroxybenzoic acid Answer

63 The END


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