Benzene and phenol are distinguished by chemical methods

Benzene and phenol are two substances that are often confused in the chemical industry. They have similarities in physical properties, but they have significant differences in chemical properties. There are many ways to distinguish between benzene and phenol, of which chemical methods are one of the most common and effective. This article will analyze how to distinguish these two substances by chemical methods from multiple angles.

1. physical properties preliminary judgment

The difference between benzene and phenol can be quickly determined by physical properties before the chemical method of differentiation.

1. color and density Benzene is a colorless transparent liquid, while phenol is a light purple or purple liquid. Because phenol contains hydroxyl groups (-OH) in the molecule, its solubility increases slightly, so the density is slightly greater than benzene (about 0.81 g/cm ³ vs 0 benzene). This can be distinguished by a simple density measurement.

2. Solubility Benzene is sparingly soluble in water and more soluble in carbon tetrachloride. The solubility of phenol in water is better, and also has good solubility with carbon tetrachloride, but compared with benzene, its solubility is higher. The two substances can be preliminarily distinguished by the difference in solubility.

2. chemical properties distinction

Chemical methods are the main means to distinguish between benzene and phenol, including the following:

1. Reactions with strong alkali Benzene is stable and does not react with strong bases such as NaOH. Phenol is acidic and can be neutralized with NaOH to generate a white hydroxide phenol precipitate. Experimental steps: take the liquid to be tested, add appropriate amount of NaOH solid, and oscillate. If a white precipitate is produced, it is phenol; if there is no reaction, it is benzene.

2. Reaction with FeCl3 Phenol has a phenolic hydroxyl group, which can react with FeCl3 solution, showing purple or red brown. Benzene does not contain phenolic hydroxyl and does not color with FeCl3. Experimental steps: take the liquid to be tested, add FeCl3 solution, and oscillate. If the solution is purple or reddish brown, it is phenol; if there is no color, it is benzene.

3. Reaction with bromine water Benzene does not react with bromine water, so its solubility in bromine water is better, and the color of bromine water will gradually fade. And phenol will react with bromine water to generate a white precipitate. Experimental steps: take the liquid to be tested and add bromine water. If the color of bromine water fades, it is benzene; if white precipitate appears, it is phenol.

3. Practical Application of Identification

In industrial production and laboratory, the identification of benzene and phenol is very common. For example, in the synthesis of organic compounds, it is often necessary to add phenol as a catalyst or to remove impurities in benzene. These two substances can be quickly and accurately distinguished by chemical methods to avoid misuse.

4. summary

By the above chemical method, benzene and phenol can be effectively distinguished. The initial judgment of physical properties can be used as a preliminary screening, while the difference in chemical reactions provides a reliable basis for accurate discrimination. Mastering these chemical methods is of great significance to scientific research and production in the chemical industry.