Chemical distinction between benzene and ethylbenzene

Benzene and ethylbenzene are two important compounds commonly used in organic chemistry, which have a wide range of applications in many fields, such as solvents, fire extinguishing agents and so on. In practice, it is essential to distinguish the differences between the two substances. Because of their significant differences in physical and chemical properties, they can be identified by chemical methods.

1. Benzene and Ethylbenzene Nomenclature Background

Benzene and ethylbenzene are named for their structural characteristics. The structure of benzene is a ring structure, the molecular formula is C6H6, is a colorless, tasteless liquid. Ethylbenzene is an isomer of benzene, the molecular formula is C6H5CH3, and the structure is more than one methyl group. Although their molecular formulas are similar, there are significant differences in physical properties and chemical reactions between the two.

2. chemical differences

1. Boiling Point Difference Benzene has a boiling point of 80.1°C and ethylbenzene has a boiling point of 119.3°C. Due to the difference in molecular weight and molecular structure, the boiling point of ethylbenzene is higher than that of benzene. Therefore, the two can be distinguished by heating and observing the vapor generation.

2. solubility difference Benzene is an organic solvent insoluble in water, while ethylbenzene is slightly soluble in water and easily miscible with water. Therefore, when mixed with water, their stratification phenomenon is different, which can be preliminarily identified by this characteristic.

3. chemical identification method

1. Use of acid-base indicators The liquid to be tested was added dropwise to the same amount of water respectively, and allowed to stand after shaking. Benzene will be immediately miscible with water and present a colorless liquid; while ethylbenzene will be layered, the upper layer is colorless, and the lower layer is grayish green. This is because ethylbenzene and water form a slightly soluble layer, and the lower organic phase reacts with the indicator in water to produce a color change.

2. Use of bromine vapor Bromine is a commonly used organic brominating reagent. Bromine vapor is introduced into the liquid to be tested to see if the bromine reacts with the organics. Both benzene and ethylbenzene undergo addition reactions with bromine, but the degree of reaction varies. In the bromine environment, the reaction rate of benzene is faster, and the reaction rate of ethylbenzene is slower.

3. Use of acidic potassium permanganate After mixing with the liquid to be tested, add acidic potassium permanganate solution and shake. Benzene will be oxidized under acidic conditions, but the reaction rate is slow; while ethylbenzene will quickly react with potassium permanganate, and the color of the solution will change from purple to colorless. This difference can be used to distinguish between the two.

4. other identification methods

1. Using the Solubility Test The liquid to be tested was added to the same amount of sodium bicarbonate solution, and the phenomenon was observed after shaking. Benzene will be quickly miscible with sodium bicarbonate solution, while ethylbenzene will be layered, the upper layer is colorless, and the lower layer has a white precipitate. This is because the methyl group in ethylbenzene reacts with sodium bicarbonate to form ethyl carbonate.

2. Use of bromine water Drop bromine water into the liquid to be tested and observe whether it is extracted. Benzene will be extracted with bromine water, but the extraction phenomenon is relatively slow; while ethylbenzene will be immediately extracted with bromine water, resulting in a lighter color of bromine water.

5. Reagent Reagent

1. Acid-base indicator: such as bromine vapor
2. Acidic potassium permanganate solution: For specific condition oxidation reaction test
3. Sodium bicarbonate solution: for solubility testing
4. Bromine water: for extraction tests

6. Considerations

In the chemical identification, need to pay attention to the following points:

1. Operation safety: in the use of bromine vapor, should ensure that the operator wearing appropriate protective equipment, to avoid bromine vapor on the operator injury.
2. Reagent: the use of reagent concentration and amount should be strictly in accordance with the experimental requirements, to avoid the reagent dosage is insufficient or excessive impact on the experimental results.
3. Environmental control: the experimental environment should be kept dry and ventilated, to avoid environmental factors on the experimental results of interference.

7. summary

Through the above chemical identification method, benzene and ethylbenzene can be easily distinguished. Although benzene and ethylbenzene are very similar in structure, they have significant differences in physical properties and chemical reactions. Mastering these chemical identification methods can not only improve the efficiency of work and study, but also play an important role in practical applications. By understanding the chemical properties of these two substances, we can use them more efficiently and contribute to social development.