Question

The compound formed as a result of oxidation of ethylbenzene by \[{\text{KMn}}{{\text{O}}_{\text{4}}}\] is:
A.benzophenone
B.acetophenone
C.benzoic acid
D.benzyl alcohol

Answer 1

Hint: Ethyl benzene is a cyclic compound. On undergoing oxidation in the presence of \[{\text{KMn}}{{\text{O}}_{\text{4}}}\], the product will be also a cyclic compound.

Complete step by step solution:
We know that the formula of ethyl benzene is \[{{\text{C}}_{\text{8}}}{{\text{H}}_{{\text{10}}}}\]. We will see what this compound will give in the presence of \[{\text{KMn}}{{\text{O}}_{\text{4}}}\].

In the above reaction, we see that ethyl alcohol gives benzoic acid during the oxidation of ethyl benzene by \[{\text{KMn}}{{\text{O}}_{\text{4}}}\].

Therefore,C is the correct option.

Additional information:
\[{\text{KMn}}{{\text{O}}_{\text{4}}}\] is a very common reagent used in the oxidation of various compounds. We can draw the structure of potassium permanganate as follows.

\[{\text{KMn}}{{\text{O}}_{\text{4}}}\] is an odourless, purple coloured crystalline solid. It is soluble in water, acetic acid, acetone, methanol, pyridine etc. It is soluble in solvents like ethanol and in other organic solvents. Potassium permanganate exists in the form of monoclinic prisms. \[{\text{KMn}}{{\text{O}}_{\text{4}}}\] is opaque with a blue metallic lustre. Potassium permanganate is a strong oxidizing agent, and it is used as an oxidant in a lot of chemical reactions.
When potassium permanganate in solid form is heated, it undergoes decomposition. The reaction is as follows:
\[{\mathbf{2KMn}}{{\mathbf{O}}_{\mathbf{4}}}\; \to {\text{ }}{{\mathbf{K}}_{\mathbf{2}}}{\mathbf{Mn}}{{\mathbf{O}}_{\mathbf{4}}}\; + {\text{ }}{\mathbf{Mn}}{{\mathbf{O}}_{\mathbf{2}}}\left( {\mathbf{s}} \right){\text{ }} + {\text{ }}{{\mathbf{O}}_{\mathbf{2}}}\]
On heating with an alkali, potassium permanganate it produces manganese and oxygen gas is evolved.
\[{\mathbf{4KMn}}{{\mathbf{O}}_{\mathbf{4}}}\; + {\text{ }}{\mathbf{4KOH}}\; \to {\text{ }}{\mathbf{4}}{{\mathbf{K}}_{\mathbf{2}}}{\mathbf{Mn}}{{\mathbf{O}}_{\mathbf{4}}}\; + {\text{ }}{\mathbf{2}}{{\mathbf{H}}_{\mathbf{2}}}{\mathbf{O}}{\text{ }} + {\text{ }}{{\mathbf{O}}_{\mathbf{2}}}\]

Note: In qualitative analysis, Potassium permanganate is used for determining the permanganate value. It is also used in the treatment of various bacterial infections.