How to distinguish between vinyl chloride and ethylene

In the chemical industry, ethylene (Ethylene) and vinyl chloride (Ethylene Dichloride) are two common organic compounds that differ significantly in their chemical and physical properties. As important raw materials in chemical production, the identification of the two is very important for the optimization of production process and quality control. This article will analyze how to distinguish these two substances in detail from three aspects: structural formula, chemical properties and physical properties.

1. structural differences

1. Structural formula of ethylene The ethylene molecule is composed of two carbon atoms and four hydrogen atoms, and the molecular formula is C₂ Halready. Its structure is a planar structure, two carbon atoms are connected by a double bond, and each carbon atom is also connected to two hydrogen atoms. In the structural formula, the presence of double bonds is an important feature of ethylene, which also makes ethylene have high chemical activity.

2. Structural formula of vinyl chloride The vinyl chloride molecule is composed of two carbon atoms, four hydrogen atoms and two chlorine atoms. The molecular formula is the dichloride state of C₂ H, and the structural formula is C₂ H₂ Cl. Its structure is similar to ethylene, but there is a chlorine atom on each side of the double bond. This structure gives vinyl chloride a stronger propensity for substitution reactions.

3. Comparison of Structural Formulas The structural formulae of ethylene and vinyl chloride are essentially the same, both being substituted forms of the C₂ Halready group. The difference is that there is no chlorine atom on both sides of the double bond in ethylene, while there is a chlorine atom on each side of the double bond in vinyl chloride. This subtle structural difference determines the physical and chemical properties of the two.

2. chemical properties of the difference

1. solubility and state Ethylene is a colorless liquid at room temperature with strong solubility and can be dissolved in most organic solvents. Vinyl chloride is a colorless liquid at room temperature and also has good solubility, but in some cases it will show a slight difference due to the different intermolecular forces.

2. reactivity Ethylene has a high activity of double bonds and is prone to reactions such as addition and polymerization, for example, polyethylene is formed in the polymerization reaction. Although the double bond of vinyl chloride is also active, the presence of its chlorine atom increases the stability of the molecule, making it slightly less reactive than ethylene.

3. substitution reaction Ethylene is prone to free radical substitution reactions under light conditions, generating a variety of chlorinated products. However, due to the presence of chlorine atoms on both sides of the double bond, the substitution reaction of vinyl chloride will be affected by chlorine atoms, and the reaction activity will be reduced.

, 3. physical properties of the difference

1. melting point and boiling point Ethylene has a melting point of -103.15°C and a boiling point of -34.7°C; vinyl chloride has a melting point of -130°C and a boiling point of -43.9°C. The melting point and boiling point of vinyl chloride are lower than that of ethylene, which is related to the difference of intermolecular forces.

2. Density The density of ethylene was 1.10 L/g and the density of vinyl chloride was 1.24 L/g. The higher density of vinyl chloride is associated with an increase in its molecular weight.

3. Color and odor Ethylene is colorless and odorless, and vinyl chloride is colorless but has a pungent odor, which makes it necessary to identify the two by odor in actual operation.

4. identification method

1. structural formula identification method Identification is carried out by using specific reagents, depending on the chemical structural formula. For example, the two compounds are mixed with bromine water respectively, and the reaction phenomenon is observed. Ethylene will react with bromine water, and bromine water will fade; vinyl chloride will not react.

2. identification method of physical properties The change of melting process is observed by heating, or the difference of dissolution rate after dissolving in different solvents is identified.

3. instrumental analysis Analysis was performed using an infrared spectrum analyzer or a nuclear magnetic resonance (NMR) instrument. The infrared spectrum and nuclear magnetic resonance spectrum of ethylene and vinyl chloride have obvious differences in some characteristic peaks, which can be identified by these characteristics.

5. Practical Application of Distinction

In industrial production, the application areas of ethylene and vinyl chloride have different emphases. Ethylene is mainly used in the production of polyolefin materials, such as polyethylene, while vinyl chloride is widely used in the production of plastics, rubber and other materials. Therefore, it is very important to distinguish the performance and use of the two for the optimization of the production process.

Summary

From the above analysis, it can be seen that the key to distinguish between vinyl chloride and ethylene lies in the subtle differences in their molecular structure, chemical properties and physical properties. Ethylene has the characteristics of high double bond activity and strong reactivity, while vinyl chloride changes in some properties due to the presence of chlorine atoms. In practical applications, these two substances can be accurately distinguished by structural analysis, physical property testing or instrumental analysis to ensure the smooth progress of the production process and the control of product quality.