Question

rection of pyrogallol with o2 and o3

Answer 1

Pyrogallol is oxidized by both O2 and O3.

1. With O2 (Oxygen): In alkaline solution, pyrogallol is rapidly oxidized by O2, turning dark brown/black, and O2 is absorbed. This is used for oxygen estimation.
2. With O3 (Ozone): Being a powerful oxidizing agent, O3 vigorously oxidizes pyrogallol, leading to its extensive degradation into simpler oxidized products like organic acids, CO2, and H2O.

Answer 2

Pyrogallol (1,2,3-trihydroxybenzene) is a strong reducing agent due to the presence of multiple adjacent hydroxyl groups on the benzene ring.

1. Reaction with O2 (Oxygen):

In alkaline solution, pyrogallol readily reacts with molecular oxygen. It is rapidly oxidized, turning the solution dark brown or black. This property is widely used in gas analysis for the quantitative absorption and removal of oxygen from gas mixtures. The reaction forms complex polymeric oxidation products, such as purpurogallin and other quinone-like structures.

The overall process is an oxidation-reduction reaction where pyrogallol is oxidized, and oxygen is reduced.

2. Reaction with O3 (Ozone):

Ozone (O3) is a much stronger oxidizing agent than molecular oxygen. Given pyrogallol's high susceptibility to oxidation, it will react vigorously with ozone. This reaction leads to the extensive oxidation and degradation of the pyrogallol molecule. The products would typically be simpler organic acids, carbon dioxide (CO2), and water (H2O), depending on the reaction conditions and stoichiometry, as the aromatic ring can be cleaved by strong oxidants like ozone.

This is also an oxidation-reduction reaction where pyrogallol is oxidized, and ozone is reduced.

Explanation of the solution:

Pyrogallol is a reducing agent. With O2 (especially in alkaline solution), it gets oxidized, and O2 is absorbed, forming dark products. With O3, a much stronger oxidant, pyrogallol undergoes vigorous oxidation, leading to its degradation into simpler, highly oxidized compounds.