Investigate the nomenclature of organic chemicals, up to C8, using IUPAC conventions, including simple methyl and ethyl branched chains

Organic Chemistry > Nomenclature >

Nomenclature of alkanes

• • Straight chained alkanes are named by replacing their alkyl names (which would be formed after removing a hydrogen atom from the structure) with –ane. For example, Methane comes from methyl.
    

    Number of carbons in linear chain	Name according to IUPAC
    1	Methane
    2	Ethane
    3	Propane
    4	Butane
    5	Pentane
    6	Hexane
    7	Heptane
    8	Octane

  • For branched chains however, the following rules are to be considered:
    • The longest carbon chain should be identified and selected as the parent chain.
    • Identify all of the substituents (groups appending from the parent chain).
    • Number the carbons of the parent chain from the end that gives the substituents the lowest numbers.
    • If the same substituent occurs more than once, the location of each point on which the substituent occurs is given. In addition, the number of times the substituent group occurs is indicated by a prefix (di, tri, tetra, etc.).
    • If there are two or more different substituents they are listed in alphabetical order using the base name.
    • If chains of equal length are competing for selection as the parent chain, then the choice goes in series to:
      • the chain which has the greatest number of side chains.
      • the chain whose substituents have the lowest- numbers.
      • the chain having the greatest number of carbon atoms in the smaller side chain.
      • the chain having the least branched side chains.

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Nomenclature of alkenes and alkynes

• Since alkenes and alkynes have double and triple bonds respectively, no single carbon molecule are present and the naming starts from molecules having 2 carbon atoms. For alkenes, the suffix from saturated hydrocarbons –ane is replaced by –ene and in case of alkynes, it is replaced by –yne.
  

  Number of carbons in linear chain	Alkene	Alkyne
  2	Ethene	Ethyne
  3	Propene	Propyne
  4	Butene	Butyne
  5	Pentene	Pentyne
  6	Hexene	Hexyne
  7	Heptene	Heptyne
  8	Octene	Octyne

• For branched chains, the following rules apply:
  • The parent chain is numbered so that the multiple bonds have the lowest numbers (double and triple bonds have priority over alkyl and halo substituents).
  • When both double and triple bonds are present, numbers as low as possible are given to double and triple bonds even though this may at times give “-yne” a lower number than “-ene”.
  • When both double and triple bonds are present, the -en suffix follows the parent chain directly and the -yne suffix follows the -en suffix (notice that the e is left off, -en instead of -ene).
  • If there is a choice in numbering not previously covered, the parent chain is numbered to give the substituents the lowest number at the first point of difference.

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Nomenclature of alcohols

• Alcohols are named by replacing the suffix -ane with -anol.
  

  Number of carbons	Name according to IUPAC
  1	Methanol
  2	Ethanol
  3	Propanol
  4	Butanol
  5	Pentanol
  6	Hexanol
  7	Heptanol
  8	Octanol

• For branched chain, the rules are:
  • The hydroxyl group takes precedence over alkyl groups and halogen substituents, as well as double bonds, in the numbering of the parent chain.
  • When both double bonds and hydroxyl groups are present, the -en suffix follows the parent chain directly and the -ol suffix follows the -en suffix.
  • If there is a choice in numbering not previously covered, the parent chain is numbered to give the substituents the lowest number at the first point of difference.

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Nomenclature of aldehydes

• Aldehydes are named by replacing the suffix -ane with -anal.
• For branched aldehydes, following rules should be considered:
• The carbonyl group takes precedence over alkyl groups and halogen substituents, as well as double bonds, in the numbering of the parent chain.
• When both double bonds and carbonyl groups are present, the -en suffix follows the parent chain directly and the -al suffix follows the -en suffix.
• There are a couple of common names which are acceptable as IUPAC names. They are shown in the examples at the end of this list but at this point these names will not be accepted by the computer. Eventually they will be accepted.

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Nomenclature of ketones

• Ketones are named by replacing the suffix -ane with -anone.
• The following rules are applied in case of naming branches:
• The carbonyl group takes precedence over alkyl groups and halogen substituents, as well as double bonds, in the numbering of the parent chain.
• When both double bonds and carbonyl groups are present, the -en suffix follows the parent chain directly and the -one suffix follows the -en suffix.
• If there is a choice in numbering not previously covered, the parent chain is numbered to give the substituents the lowest number at the first point of difference.

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Nomenclature of carboxylic acids

• Carboxylic acids are named by counting the number of carbons in the longest continuous chain including the carboxyl group and by replacing the suffix -ane of the corresponding alkane with -anoic acid.
• Rules for naming branches:
• The carboxyl group takes precedence over alkyl groups and halogen substituents, as well as double bonds, in the numbering of the parent chain.
• If the carboxyl group is attached to a ring the parent ring is named and the suffix -carboxylic acid is added.
• When both double bonds and carboxyl groups are present, the -en suffix follows the parent chain directly and the -oic acid suffix follows the -en suffix.
• There are several common names which are acceptable as IUPAC names. They are shown in the examples at the end of this list but at this point these names will not be accepted by the computer. Eventually they will be accepted.
• If there is a choice in numbering not previously covered, the parent chain is numbered to give the substituents the lowest number at the first point of difference.

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Nomenclature of amines

• Unlike the rest of the organic compounds, amines lack special rules when it comes to naming them.
• They are named like ethers, the alkyl (R) groups attached to the nitrogen are put in alphabetical order with no spaces between the names and these are followed by the word amine.
• The prefixes di- and tri- are used if two or three of the alkyl groups are the same.

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Nomenclature of halogenated organic compounds

• Halogenated hydrocarbons are named by adding the name of the halogen as a prefix to the hydrocarbon. For example, bromine combined with ethane is termed as Bromoethane, 4 chlorine groups with methane is called tetrachloromethane.
• The carbon atoms should be numbered from the position that gives lower series of number.

Reference:

How to name organic compounds using the IUPAC rules