Question

Oxidation of which of the following by air in presence of vanadium pentoxide gives phenol
A. Toluene
B. Benzene
C. Benzaldehyde
D. Phenylacetic acid

Answer 1

Hint: Oxidation of an organic compound is the process of reaction of a compound without oxygen that happens in the presence of an oxidising agent. Phenol is an aromatic organic compound having the molecular formula C₆H₅OH.

Complete Step by Step Answer:
Phenol has a phenyl group (\[{C_6}{H_5}\]) connected to a hydroxyl group (−OH).
It is mildly acidic and needs cautious handling as it can induce chemical burns.
Oxidation of a compound gives phenol. We have to find out the compound.

A. Toluene
Toluene is a substituted aromatic hydrocarbon.
It has no colour, a water-insoluble liquid with a smell like that of paint thinners.
It is a mono-substituted benzene derivative, having a methyl group (\[C{H_3}\] ) attached to a phenyl group.
Its IUPAC name is methylbenzene.
Oxidation of toluene gives benzoic acid and benzaldehyde in presence of strong oxidising agents like potassium permanganate.
It doesn't give phenol on oxidation with vanadium pentoxide.
So, A is incorrect.

B. Benzene
It is an organic chemical compound having the chemical formula \[{C_6}{H_6}\].
It is composed of six carbon atoms bound in a planar ring with one hydrogen atom connected to each carbon atom.
Benzene on treatment with air in the presence of vanadium pentoxide forms at \[300^\circ C\] temperature and forms phenol.
The reaction happens as follows:


Image: Formation of phenol from benzene.
So, B is correct.

C. Benzaldehyde
Benzaldehyde when exposed to air readily undergoes oxidation by itself to form benzoic acid.
So, C is incorrect.

D. Phenylacetic acid
It is an organic compound comprising a phenyl group and a carboxylic acid group.
It undergoes oxidation to form benzaldehyde.
So, D is incorrect.
Therefore, benzene in reaction with air in presence of vanadium pentoxide forms phenol.
So, option B is correct.

Note: Benzene reacts with air in presence of vanadium pentoxide at \[300^\circ C\] to form phenol. This is known as partial oxidation. But when one molecule of benzene reacts with two molecules of vanadium pentoxide and oxygen at \[500^\circ C\]we get maleic anhydride as the main product.