What is nascent oxygen and how does it relate to potassium permanganate?

Potassium permanganate, KMnO₄, is an inorganic salt composed of K⁺ and MnO₄⁻ (Mn in the +7 oxidation state). It is a purple–black crystalline solid that dissolves in water to give a purple solution.

Oxidizing Behaviour

KMnO₄ is a strong oxidizing agent in all media, but the number of electrons accepted per MnO₄⁻ depends on the medium:

• Acidic:MnO₄⁻ → Mn²⁺ (accepts 5 e⁻)
• Neutral:MnO₄⁻ → MnO₂(s) (accepts 3 e⁻)
• Basic/alkaline:MnO₄⁻ → MnO₄²⁻ (accepts 1 e⁻, green manganate)

“Nascent Oxygen”

The term nascent oxygen [O] is a pedagogical way to denote the effective oxygen supplied by strong oxidants such as KMnO₄ and K₂Cr₂O₇ during oxidation reactions (free O atoms are not actually released in solution).

Oxidation of Ethanol

In acidic medium, KMnO₄ oxidizes ethanol to acetic acid. Using [O] to represent oxidizing oxygen:

CH₃CH₂OH + 2[O] → CH₃COOH + H₂O

Note on Dichromate

With acidified K₂Cr₂O₇, ethanol is similarly oxidized while chromium(VI) is reduced to chromium(III) sulfate, Cr₂(SO₄)₃, which is green—a characteristic product of dichromate reduction, not permanganate.