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🥼organic chemistry review

Peroxyl Radicals

Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025

Definition

Peroxyl radicals are highly reactive chemical species that contain an oxygen-oxygen bond with an unpaired electron. They are formed during the process of autoxidation, where organic molecules react with molecular oxygen, and play a crucial role in various radical reactions.

5 Must Know Facts For Your Next Test

  1. Peroxyl radicals are formed during the initiation step of radical chain reactions, where a reactive species abstracts a hydrogen atom from an organic molecule.
  2. The high reactivity of peroxyl radicals is due to the presence of the oxygen-oxygen bond, which makes them highly electrophilic and capable of abstracting hydrogen atoms from other molecules.
  3. Peroxyl radicals can propagate radical chain reactions by abstracting hydrogen atoms from other organic molecules, leading to the formation of new radicals and the continued propagation of the reaction.
  4. Lipid peroxidation is a significant source of peroxyl radicals in biological systems, where they can cause damage to cellular membranes and other biomolecules.
  5. Antioxidants, such as vitamins C and E, can neutralize peroxyl radicals by donating a hydrogen atom, effectively breaking the radical chain reaction and preventing further oxidative damage.

Review Questions

  • Describe the role of peroxyl radicals in the process of autoxidation.
    • Peroxyl radicals are the key intermediates in the autoxidation process, where organic molecules react with molecular oxygen. During the initiation step, a reactive species abstracts a hydrogen atom from an organic molecule, forming a carbon-centered radical. This carbon-centered radical then reacts with molecular oxygen to form a peroxyl radical. The peroxyl radicals can then abstract hydrogen atoms from other organic molecules, propagating the radical chain reaction and leading to the formation of more radicals, including additional peroxyl radicals.
  • Explain the relationship between peroxyl radicals and lipid peroxidation.
    • Lipid peroxidation is a significant source of peroxyl radicals in biological systems. The process begins when a reactive species, such as a hydroxyl radical, abstracts a hydrogen atom from a fatty acid chain within a lipid molecule. This forms a carbon-centered lipid radical, which then reacts with molecular oxygen to produce a peroxyl radical. The peroxyl radical can then abstract another hydrogen atom from a neighboring lipid molecule, creating a new carbon-centered lipid radical and propagating the lipid peroxidation chain reaction. This cycle of radical formation and propagation can lead to extensive cellular damage, as the peroxyl radicals and other reactive species attack and disrupt cellular membranes and biomolecules.
  • Evaluate the role of antioxidants in neutralizing the effects of peroxyl radicals.
    • Antioxidants play a crucial role in neutralizing the harmful effects of peroxyl radicals. By donating a hydrogen atom to a peroxyl radical, antioxidants can effectively break the radical chain reaction and prevent further oxidative damage. For example, vitamins C and E are potent antioxidants that can scavenge peroxyl radicals, protecting cellular membranes and other biomolecules from oxidative stress. The ability of antioxidants to neutralize peroxyl radicals is essential for maintaining cellular homeostasis and preventing the development of various diseases associated with oxidative damage, such as cardiovascular disease, cancer, and neurodegenerative disorders. The balance between the production of peroxyl radicals and the availability of antioxidants is a key factor in determining the overall oxidative status of the body.