Introduction

The oxidation of alkenes represents a fundamental reaction in organic chemistry, particularly important for synthesizing valuable organic compounds. This article explores the different conditions and products of alkene oxidation using potassium permanganate (KMnO₄) as the oxidizing agent.

Reaction Conditions and Products

Mild Oxidation (Cold, Dilute KMnO₄)

Under cold, dilute conditions in neutral or alkaline medium, KMnO₄ performs a selective oxidation known as dihydroxylation. This reaction adds two hydroxyl groups (OH) to adjacent carbons of the double bond, forming a 1,2-diol:

$$R-CH=CH-R' + KMnO4 + H2O \\-> R-CH(OH)-CH(OH)-R' + MnO2 + KOH$$

Strong Oxidation (Hot, Concentrated KMnO₄)

Under hot, acidic conditions with concentrated KMnO₄, the oxidation proceeds through initial dihydroxylation followed by C-C bond cleavage. The products depend on the alkene's structure:

Practical Examples

1. Oxidation of Ethene

Under strong oxidation conditions:

$${CH2=CH2 + 3[O] -> 2CO2 + 2H2O}$$

2. Oxidation of Propene

Under strong oxidation conditions:

$${CH3-CH=CH2 + 3[O] -> CH3COOH + CO2 + H2O}$$

3. Oxidation of 2-Methylpropene

Under strong oxidation conditions:

$${(CH3)2C=CH2 + 2[O] -> (CH3)2CO + HCOOH}$$

Key Points to Remember