Why does aniline turn brown upon standing? Does it also turn brown upon heating?
Aniline, a primary aromatic amine, can turn brown upon standing due to oxidation. This process occurs when air reacts with aniline and causes it to undergo auto-oxidation, resulting in the formation of colored compounds, including a brownish substance. The exact mechanism of this reaction is complex and involves the formation of radical species.
Furthermore, aniline can also turn brown upon heating, but the exact color change and reaction mechanism may vary depending on the specific conditions. At high temperatures, aniline can undergo various chemical transformations, including polymerization and decomposition, which can result in the formation of brown-colored byproducts.
To explore this phenomenon further, you could conduct a simple experiment. Start by taking a small amount of aniline in a test tube and observe its color. Then, leave the test tube open to the air for a few hours and observe any changes in color. Additionally, you can heat another sample of aniline in a controlled manner, either by using a Bunsen burner or a hot plate, and observe the color change during and after the heating process.
By performing these experiments, you will be able to directly observe the color changes associated with aniline upon standing and upon heating, deepening your understanding of their underlying chemical processes.