Compounds containing more than one double bond are said to be conjugated if they possess a series of adjacent sp² centers. In a compound such as this, the adjacent p-orbitals overlap to form a continuous p-system, as seen in the graphic below.

Polyenes are named as are simple alkenes, using the multipliers di-, tri-, etc. to indicate the number of double bonds and numbers to show their positions.

As with simple alkenes:

1. Find the longest chain containing the double bonds; the name of the parent hydrocarbon is taken from the longest continuous chain of carbon atoms containing the double bonds.

2. Number the chain, giving the double bonds the lowest possible number; use multipliers to indicate the total number of double bonds (di, tri, tetra, etc.) Recall that in constructing the name, substituents are arranged in alphabetical order, without regard for these multipliers.

3. For cycloalkenes, begin numbering at one double bond and proceed through the double bond in the direction to generate the lowest number at the first point of difference.

4. If appropriate, assign stereochemistry using the E-Z designation.

The rules for assigning E-Z designations are as follows:

1. rank atoms directly attached to the double bond according to their atomic number
2. if there is a "tie" at any substituent, look at the second, third, etc., until a difference is found
3. multiple bonds count as multiples of that same atom
4. if the highest priority groups are on the same side of the double bond, the molecule is Z; if the highest priority groups are on opposite sides, the molecule is E

Examples: