IUPAC Nomenclature

Alkanes

  1. The name for an alkane with an unbranched chain of carbons consists of a prefix indicating the number of carbons in that chain, followed by the suffix -ane.
  2. For branched-chain alkanes, take the longest chain of carbon atoms as the parent chain, which becomes the root name.
  3. Give each substituent on the parent chain a name and a number. The number shows the carbon atom of the parent chain to which the substituent is bonded. Use a hyphen following the number.
  4. If there is one substituent, number the parent chain from the end that gives the substituent the lower number.
  5. If the same substituent occurs more than once, number the chain from the end that gives the lower number to the substituent encountered first. Indicate the number of times the substituent occurs by a prefix (di, tri, tetra, ...). Separate position numbers by commas.
  6. If there are two or more different substituents, list them in alphabetical order and number the chain from the end that gives the lower number to the substituent encountered first. If there are different substituents in equivalent positions on opposite ends of the parent chain, give the substituent of lower alphabetical order the lower number
  7. Do not include counting prefixes (di, tri, tetra, ...) in alphabetizing (also do not include sec-, tert, etc). Example: ethyl comes before dimethyl.

Alkenes

  1. Find the longest carbon chain that includes the double bond. Indicate the length of the parent chain as in (1) above, except substitute "-ene" for "-ane" to indicate that there is a double bond.
  2. Number the chain from the end that gives the lower set of numbers to the carbon atoms of the double bond (this takes precedence over (4) above). Designate the position of the double bond by the number of its first carbon.
  3. Branched alkenes and those with substituents follow the rules above.
  4. When needed, precede the name with trans- or cis- to indicate the correct isomer at the double bond.
  5. If there is more than one double bond, place di-, tri-, etc immediately before -ene in the name (no hyphens here).