Use the following guide to name alkenes according to IUPAC standards.

  1. Number the longest chain containing the double bond, starting with the end closest to the double bond. If the same number of carbons surrounds the double bond, begin numbering at the end nearest the first branch point.
  2. Name the side chains according to branched hydrocarbon rules.
  3. For the parent chain, write, in order, the numerical name (i.e. prop- or hex-), the numerical position of the first carbon in the double bond, and end with the suffix “-ene”. For multiple double bonds, number the parent chain so that the double bonds have the lowest possible numerical positions. Add the numerical prefix that corresponds to the number of double bonds present to the suffix “-ene” (i.e. -diene, triene).
  4. Assign the necessary stereochemistry to each double bond as follows:
    1. No stereochemistry is needed for double bonds with 3 or more hydrogens, or if one end of the double bond has the same substituents. Compare the side chain(s) on each carbon in the double bond(s). The attachments that contain more carbons have the higher priority over other attachments.
    2. Split the double bond in half lengthwise through the carbons. If the attachments with the highest priority are on the same side, then the double bond is designated “Z” (think Zame Zide). If they are on opposite sides, the double bond is designated “E”.
    3. Write the numerical position and the stereochemistry for each double bond, separating multiple designations by commas (i.e. (2E,4Z)).
  5. Rings hold naming priority when they contain side chains with alkenes. Name the side chain according to alkene rules; name the compound according to cyclic hydrocarbon rules.
  6. For rings that contain double bonds:
    1. Double bonds have top priority when numbering the ring. Otherwise, follow the same numbering format used in naming cyclic hydrocarbons.
    2. Change the suffix from “ane” to “ene”.
    3. To name rings with multiple double bonds, include the numerical positions and prefixes before the suffix “ene” for the parent ring, similar to naming branched alkenes.