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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. 26.1 Nomenclature of Hydrocarbons (SB p.34). Nomenclature : naming of compounds.

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Systematic Nomenclature

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  1. Chapter 26 Systematic Nomenclature 26.1Nomenclature of Hydrocarbons 26.2Nomenclature of the Derivatives of Hydrocarbons 26.3Nomenclature of the Derivatives of Aromatic Hydrocarbons

  2. 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. 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.

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

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

  25. 26.2 Nomenclature of the Derivatives of Hydrocarbons (SB p.41) 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 fluoro- chloro- bromo- iodo- alkoxy- (e.g. methoxy-) azo- nitro- methylphenyl Nomenclature of Compounds with One Type of Functional Group Compounds with functional groups that must be designated as prefixes

  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) Group General formula Suffix Systematic name Structural formula Carboxylic acid RCO2H -oic acid alkanoic acid Ester RCO2R’ -oate alkyl alkanoate Acyl chloride ROCl -oyl chloride alkanoyl chloride Amide RCONH2 -amide alkanamide Compounds with functional groups that may be designated as prefixes or suffixes

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

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

  33. 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. 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. 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. 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. 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. 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) (a) 3,4-Dimethylpentanoic acid (b) Pentan-2-ol (c) 3,4-Dimethylhexanal (d) N,N-Dimethylpropanamide Check Point 26-2 Give the IUPAC name for each of the following compounds: (a) (b) (c) (d) Answer

  42. 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)

  44. 26.2 Nomenclature of Derivatives of Hydrocarbons (SB p.47)

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

  47. 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. 26.2 Nomenclature of Derivatives of Hydrocarbons (SB p.49) Example 3: 3-chloro-2-iodobutanamide Principal functional group: Parent chain:

  49. 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. 26.2 Nomenclature of Derivatives of Hydrocarbons (SB p.50) Example 5: 4-amino-2-phenylhexanal Principal functional group: Parent chain:

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