Question

Why is the conversion of ethanol to ethanoic acid an oxidation reaction?
A. Carbon is oxidized
B. The hydrogen oxidation number is changed
C. Carbon is reduced
D. Carbon undergoes disproportionation

Answer 1

Hint: To answer this question you should first write the equation involved in the conversion of ethanol to ethanoic acid. Then, assign the oxidation number of each atom i.e. carbon and oxygen to answer the question correctly.

Complete step by step answer:
We can write the conversion of ethanol to ethanoic acid as:
$CH_{ 3 }CH_{ 2 }OH\quad +\quad KMnO_{ 4 }(Alkaline)\quad \rightarrow \quad CH_{ 3 }COOH$

If you can see the above change carefully you will notice that in this change one extra Oxygen (O) atom has been added and two Hydrogen (H) atoms are being removed from ethanol ($CH_{ 3 }CH_{ 2 }OH$) molecule to convert it into ethanoic acid ($CH_{ 3 }COOH$). The addition of Oxygen and removal of Hydrogen is known as oxidation.
Both these addition and removal are occurring on the same carbon. Hence, we can say that carbon is oxidized here.

Therefore, we conclude that the correct answer to this question is option A.

Additional information:
We should also know that the other most common oxidants are Jones reagent, PCC in DMF, Heyns oxidation and ruthenium tetroxide ($RuO_{ 4 }$)

Note: We should also know that, under controlled conditions, $KMnO_{ 4 }$ oxidizes alcohols to carboxylic acids efficiently. This reaction was first described in detail by Fournier, which is typically carried out by adding $KMnO_{ 4 }$ to a solution of the alcohol in an alkaline solution.