Question

Write oxidation reactions of potassium permanganate. (any four)

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Answer 1

Explanation:

Potassium permanganate, KMnO4, is a powerful oxidizing agent, and has many uses in organic chemistry.

Introduction

Of all the oxidizing agents discussed in organic chemistry textbooks, potassium permanganate, KMnO4, is probably the most common, and also the most applicable. As will be shown below, KMnO4 can be utilized to oxidize a wide range of organic molecules. The products that are obtained can vary depending on the conditions, but because KMnO4 is such a strong oxidizing agent, the final products are often carboxylic acids.

The half-reaction and oxidation potential

Mn(VII) is reduced under acidic conditions to Mn(IV) or Mn(II) according to the half-reactions shown below, with the indicated cell potentials1

MnO−4+4H++3e−→MnO2+2H2OEo=1.68V(1)

MnO−4+8H++5e−→Mn2++4H2OEo=1.5V(2)

MnO−4+2H2O+3e−→Mn2++4OH−Eo=0.6V(3)

General Reactivity with Organic Molecules

KMnO4 is able to oxidize carbon atoms if they contain sufficiently weak bonds, including

Carbon atoms with π bonds, as in alkenes and alkynes

Carbon atoms with weak C-H bonds, such as

C-H bonds in the alpha-positions of substituted aromatic rings

C-H bonds in carbon atoms containing C-O bonds, including alcohols and aldehydes

Carbons with exceptionally weak C-C bonds such as

C-C bonds in a glycol

C-C bonds next to an aromatic ring AND an oxygen

KMnO4 also oxidizes phenol to para-benzoquinone.