Drawing Resonance Forms for a Radical

Draw three resonance forms for the pentadienyl radical, where a radical is a substance that contains a single, unpaired electron in one of its orbitals, denoted by a dot ((..

S t r a t e g y

Find the three-atom groupings that contain a multiple bond next to an atom with a p orbital.

S o l u t i o n

The unpaired electron is on a carbon atom next to a C5C bond, giving a typical three-atom grouping that has two resonance forms.

In the second resonance form, the unpaired electron is next to another double bond, giving another three-atom grouping and leading to another resonance form.

Thus, the three resonance forms for the pentadienyl radical are: