What Does Potassium Permanganate Oxidize Ethanol To?

Step 1 — Ethanol → Ethanal (Acetaldehyde): C₂H₅OH → [O] → CH₃CHO (Primary alcohol → Aldehyde)

Step 2 — Ethanal → Ethanoic Acid (Acetic Acid): CH₃CHO → [O] → CH₃COOH (Aldehyde → Carboxylic acid)

Overall reaction: C₂H₅OH → [KMnO₄/H⁺] → CH₃COOH Ethanol → Acetic acid (Ethanoic acid)

So, potassium permanganate oxidizes ethanol to acetic acid (ethanoic acid).

The product depends on the oxidizing conditions:

1. Acidic KMnO₄ (KMnO₄/H₂SO₄ or KMnO₄/HCl): • Strongly oxidizing conditions • Primary alcohols → Carboxylic acids (all the way) • Ethanol → Ethanoic acid (acetic acid)

2. Neutral/Alkaline KMnO₄: • Milder conditions • Can give complete oxidation to CO₂ and H₂O

3. Other oxidizing agents: • K₂Cr₂O₇ / H₂SO₄ (acidified dichromate): also oxidizes ethanol to acetic acid • PCC (Pyridinium chlorochromate): oxidizes primary alcohol to aldehyde only (stops at ethanal)

Key observation: • KMnO₄ solution is purple/violet in colour • After oxidizing ethanol, the colour decolorizes (turns colourless) • This decolorization is evidence of oxidation • KMnO₄ is reduced from Mn⁷⁺ to Mn²⁺ (colourless manganese ions in acidic medium) or Mn⁴⁺ (brown MnO₂ in neutral medium)

This colour change is used as a test for the presence of reducing agents (alcohols, aldehydes).

Type of alcohol | With strong oxidant (KMnO₄/H⁺) | With mild oxidant (PCC) Primary (e.g., ethanol) | Aldehyde → Carboxylic acid | Aldehyde only Secondary (e.g., propan-2-ol) | Ketone | Ketone Tertiary (e.g., tert-butanol) | No reaction (no α-H on correct side) | No reaction

Ethanol is a primary alcohol, so it is oxidized all the way to acetic acid by KMnO₄.