Potassium Permanganate

KMnO4

Potassium Permanganate

pyrolusite

MnO2

Preparation STEP 1

fusing MnO2 with KOH or K2CO3 in presence of O2 or KNO3 which gives green colour and formation of K2MnO4 (potassium manganate)

Preparation STEP 2

K2MnO4 is then extracted with water and is treated with Cl2 or O3 or CO2 and converts manganate to permanganate

Preparation comercially of permanganate

fusion of MnO2 with KOH followed by electrolytic oxidation of manganate

Preparation in lab

A manganese (ll) ion salt is oxidized to by peroxidisulfate (S2O8) to permanganate

Physical property

• purple coloured crystalline compound

• moderately soluable in water at room temp

Effect of heating

2KMnO4 on heating at 513K gives K2MnO4 + MnO2 + O2

On treatment with conc.H2SO4

it forms manganese heptoxide which decomposes explosively on heating

Mn2O7

explosive

Oxidizing agent in which medium?

weak alkaline, neutral, acidic solutions

Why is HCl not used in acidification of KmnO4

cuz KMnO4 oxidizes HCl to Cl2

Uses

• favored oxidant in preparative org chem

• bleaching of wool, cotton, silk

• decolourization of oil