A little H₂O₂ Chemistry

How is H₂O₂ formed?

In nature - By combining water with oxygen - By adding 2 electrons to molecular oxygen

2 H₂O + ³ O₂ →  2 H₂O₂

In biological systems

(1) By 2 Superoxides joining Together

O₂^•-+ O₂^•- + 2H⁺ → H₂O₂ + ³ O₂

Or

(2) By Antibodies - which generate H₂O₂ from singlet oxygen ( ¹O₂*) using H₂O (antibodies provide electron source in a catalytic process - possibly as a protective mechanism against ¹O₂*)

¹O₂* + H2O → H₂O₂

The active ability of H₂O₂

H₂O₂ is neutrally charged, and can diffuse deeply into cells - H₂O₂ is actually considered a poorly reactive non-radical, but its "strength" lies in the extremely reactive Hydroxyl Radical (OH•)it can produce:

• Hydroxyl radical (OH•) produced from H₂O₂ by:
  • H₂O₂ oxidation of transition metal ions (especially iron contained in hemoglobin)

H₂O₂ + Fe²⁺ → OH^• + OH^- + Fe³⁺ (known as the Fenton reaction)

• H₂O₂ reacting with Photon or Electron Energy (i.e. Reduction of H₂O₂)

H₂O₂ +e^- → OH^• + OH^-

The OH^• radical is a potent biological oxidant capable of destroying toxins and microbial infection. Almost every time the hydroxyl radical bumps into another molecule it pulls off a hydrogen atom to then become harmless water, while simultaneously producing another radical in what is left of the other molecule.

-   Neutrophils can also produce the oxidizing agent hypochlorous acid (HOCl) - by the well-established reaction of H₂O₂ with a chlorine ion:

H₂O₂ + Cl^-→ HOCl + OH^-