Question

The Fenton reaction leads to free radical generation when

• A. Radiant energy is absorbed by water
• B. Hydrogen peroxide is formed by myeloperoxidase
• C. Ferrous ions are converted into ferric ions
• D. Nitric oxide is converted into peroxynitrite anion

Hint:

Fenton reaction: Fe2+ + H2O2 gives Fe3+ + hydroxyl radical.

Answer 1

The Correct Option is C

Step 1: Understand the Fenton reaction.
The Fenton reaction is a chemical reaction in which hydrogen peroxide reacts with a transition metal, usually iron, to make a highly reactive hydroxyl free radical. It is one of the main ways the body generates dangerous free radicals from hydrogen peroxide.

Step 2: Write the reaction.
The reaction is
\[ Fe^{2+} + H_2O_2 \rightarrow Fe^{3+} + OH^{-} + OH^{\bullet} \]
Here the ferrous ion (\(Fe^{2+}\)) donates an electron to hydrogen peroxide, breaking it apart and forming the hydroxyl radical (\(OH^{\bullet}\)). In the process the ferrous ion is oxidised to the ferric ion (\(Fe^{3+}\)).

Step 3: Check each option against this reaction.
Radiant energy absorbed by water can split water into radicals through radiolysis, but this is not the Fenton reaction, it is a separate, radiation-driven process.
Hydrogen peroxide being formed by myeloperoxidase describes how the enzyme system makes reactive oxygen species inside phagocytes, it is not the Fenton step itself, which needs a metal ion, not an enzyme.
Nitric oxide turning into peroxynitrite anion is a different free radical pathway, where nitric oxide combines with superoxide, again this does not use iron and is not Fenton chemistry.
The conversion of ferrous ions into ferric ions is exactly the electron transfer step that defines the Fenton reaction and directly produces the hydroxyl radical.

Step 4: Final answer.
Free radical generation by the Fenton reaction happens when ferrous ions are converted into ferric ions.
\[ \boxed{\text{Ferrous ions are converted into ferric ions}} \]