Differentiation between phenol and ethanol by chemical test

In the field of chemistry, phenol and ethanol are two common organic compounds. Although their chemical structures are similar, due to the significant differences in their properties and reaction characteristics, it is very important to distinguish between phenol and ethanol in laboratory analysis. This article will help you understand how to effectively distinguish these two substances through several classic chemical test methods.

1. Phenol and ethanol structure difference

Understanding the chemical structures of phenol and ethanol is essential to distinguish between them. Phenol (C; H; OH) is an aromatic compound whose molecular structure contains a benzene ring and a hydroxyl (OH) group. Ethanol (C₂ H∞OH), on the other hand, is a saturated alcohol compound containing an ethyl group (C₂ H∞H) and a hydroxyl group in the molecule. Although both contain a hydroxyl group, phenol is more acidic than ethanol due to the presence of a benzene ring.

2. The use of acid and alkali reagents to distinguish between phenol and ethanol

Phenol is more acidic and can react with sodium hydroxide (NaOH) solution to form phenol sodium salt, while ethanol does not. Therefore, the use of sodium hydroxide solution is a common method to distinguish between phenol and ethanol. The specific operation is to add a small amount of phenol and ethanol to the sodium hydroxide solution, the phenol will react immediately, the solution becomes colorless or slightly yellow, while the ethanol will not react, and the solution remains the same.

3. Potassium ferricyanide test

Another common method of differentiation is the potassium ferricyanide test. Phenol can undergo a characteristic blue precipitation reaction in potassium ferricyanide solution, while ethanol does not. This is because the benzene ring in the phenol molecule can form a stable complex with iron ions, resulting in a blue precipitate. This test was conducted by mixing phenol or ethanol with a solution of potassium ferricyanide, respectively, and observing whether a blue precipitate was produced.

4. Bromine water reaction

Bromine water (Br₂ water) is another effective reagent to distinguish between phenol and ethanol. At room temperature, phenol can react with bromine water to form a white precipitate of dibromophenol, and the color of bromine water will disappear. However, ethanol reacts slowly with bromine water at room temperature and does not produce white precipitate. To perform this test, bromine can be added dropwise to a solution of phenol or ethanol to observe whether a precipitate is formed and the color of the solution changes.

5. Ferric chloride test

The ferric chloride (FeCl3) reagent can be used to distinguish between phenol and ethanol. When phenol reacts with ferric chloride solution, a purple complex is usually formed, while ethanol does not. The principle of this experiment is that the hydroxyl group in the phenol molecule reacts with the iron ion to form a purple complex. The method of operation is to add ferric chloride solution dropwise to phenol or ethanol solution and observe whether purple color appears.

6. Summary

Through the several chemical tests mentioned above, you can easily distinguish between phenol and ethanol. Although both phenol and ethanol contain hydroxyl groups, due to the strong acidity of phenol and its unique reaction characteristics, such as sodium phenolate, blue precipitation with potassium ferricyanide, dibromophenol, etc., while ethanol does not have these significant chemical reactions. Therefore, mastering these test methods is not only very helpful for academic research, but also has practical significance in industrial applications.

The chemical test to distinguish between phenol and ethanol is the basic operation in organic chemical analysis. By using experimental methods such as acid-base reaction, potassium ferricyanide test, and bromine water reaction, we can accurately judge these two chemical substances and avoid misuse in practical applications.