Pyrogallol is a white crystalline powder that is soluble in water and alkaline solutions. When it is exposed to air, it rapidly absorbs oxygen molecules from the atmosphere. This reaction is catalyzed by the presence of an alkaline solution, such as sodium hydroxide, which increases the pH of the solution and enhances the oxidizing power of pyrogallol.
The chemical reaction between oxygen and pyrogallol is a redox reaction, which involves the transfer of electrons from one molecule to another. In this case, oxygen acts as an oxidizing agent and pyrogallol acts as the reducing agent. The oxygen molecules react with the hydroxyl groups (-OH) of pyrogallol, which are electron-rich and can donate electrons to the oxygen atoms.
The reaction between oxygen and pyrogallol generates a series of intermediate products, including quinone, which is a yellow-brown compound that contributes to the dark color of the solution. The quinone molecule is formed by the oxidation of pyrogallol, where two hydroxyl groups are lost and a double bond is formed between two carbon atoms.
The presence of oxygen, as well as the concentration and pH of the alkaline solution, can affect the rate and extent of the pyrogallol oxidation reaction. For instance, increasing the oxygen concentration or the pH of the solution can accelerate the reaction, while decreasing these factors can slow down the reaction.
The ability of pyrogallol to scavenge oxygen molecules has important implications in several fields of science and technology. For example, in photography, pyrogallol is used as a developing agent for black and white films, where the oxidation of silver halides by pyrogallol generates metallic silver grains that form the image.
In air analysis, pyrogallol can be used to measure the level of dissolved oxygen in water samples, which is an indicator of the health of aquatic ecosystems. In antioxidant research, pyrogallol is used as a standard compound to assess the antioxidant capacity of natural and synthetic molecules, as it can readily react with oxygen and prevent oxidative damage.
In conclusion, the chemical reaction between oxygen and pyrogallol in alkaline solutions is a redox reaction that generates intermediate products and leads to the formation of a dark brown color. This process has numerous applications in various fields, including photography, air analysis, and antioxidant research. By understanding the mechanism and kinetics of this reaction, scientists can exploit the properties of pyrogallol to advance their research and technology. So, if you want to learn more about oxygen absorption by pyrogallol, keep exploring the fascinating world of inorganic chemistry.