The pentadienyl radical, H2C=CH-CH=CH-CH2·, has its unpaired electron delocalized over three carbon atoms.


(h) Add an electron to the pentadienyl radical to give the pentadienyl anion. Which carbon atoms share the negative charge? Does this picture agree with the resonance picture?

Verified step by step guidance

1. Identify the structure of the pentadienyl radical, which is H2C=CH-CH=CH-CH2·. The unpaired electron is delocalized over the carbon atoms involved in the conjugated system.
2. Add an electron to the pentadienyl radical. This electron pairs with the unpaired electron, resulting in the formation of the pentadienyl anion.
3. Determine the distribution of the negative charge in the pentadienyl anion. The negative charge is likely to be delocalized over the carbon atoms that were part of the conjugation in the radical, particularly focusing on the carbons involved in double bonds and the terminal carbon atom.
4. Draw resonance structures to visualize the delocalization of the negative charge across different carbon atoms in the pentadienyl anion. This helps in understanding how the charge is shared among the carbon atoms.
5. Compare the resonance structures with the initial radical structure to confirm if the distribution of the negative charge in the anion agrees with the delocalization pattern observed in the radical. This step checks the consistency between the radical and its corresponding anion form.

Key Concepts

Radicals and Anions

Radicals are species that contain an unpaired electron, making them highly reactive. In contrast, anions are negatively charged species that have gained an electron. The pentadienyl radical has an unpaired electron that can be paired with an additional electron to form the pentadienyl anion, which will have a negative charge distributed among the carbon atoms.

Delocalization of Charge

Delocalization refers to the spreading of electrons across multiple atoms rather than being localized between two. In the case of the pentadienyl anion, the negative charge can be delocalized over the carbon atoms involved in the conjugated system, which stabilizes the anion and influences its reactivity and properties.

Resonance Structures

Resonance structures are different ways of drawing a molecule that represent the same arrangement of atoms but differ in the placement of electrons. For the pentadienyl anion, resonance structures can illustrate how the negative charge is shared among the carbon atoms, providing a more accurate depiction of the electron distribution and stability of the anion.