How to distinguish between chloropropene and chloropropane

In the chemical industry, chloropropene (C3H4Cl) and chloropropane (C3H8Cl) are two chlorinated olefins that are often mentioned and easily confused. In order to help readers better understand their differences and applications, this article will analyze the molecular structure, physical properties, chemical properties, and application fields in detail, and discuss how to distinguish these two substances in practical work.

1. basic structure and molecular composition

In terms of molecular structure, both chloropropene and chloropropane are formed by substituting one or more hydrogen atoms in a propane or propylene molecule. Specifically:

1. Allyl chloride (C3H4Cl) In the structure of chloropropene, a chlorine atom is attached to one carbon atom, while the other two carbon atoms are combined with hydrogen atoms to form a double bond (C = C) in the overall structure. This structure makes the chloropropene unsaturated.

2. Chloropropane (C3H8Cl) In the structure of chloropropane, a chlorine atom is connected to one carbon atom, and the other two carbon atoms are combined with hydrogen atoms. The whole molecule is completely saturated and has no double bonds.

This slight structural difference makes the physical and chemical properties of chloropropene and chloropropane significantly different.

2. Physical Properties Comparison

1. molecular weight The molecular weight of allyl chloride is 49.48g/mol, while the molecular weight of chloropropane is 50.49g/mol. The two are very close, but the structural differences result in slightly different molecular weights.

2. Density At normal temperature, the density of chloropropene is 1.86g/cm³, which is slightly higher than the density of chloropropane, 1.42g/cm³. This is due to the presence of double bonds in the chloropropene molecule, which makes the molecular structure more compact.

3. melting point and boiling point Chloropropene has a melting point of -47.7°C and a boiling point of -34.3°C; chloropropane has a melting point of -94.6°C and a boiling point of -63.3°C. The melting point and boiling point of chloropropene are higher than those of chloropropane because of the presence of unsaturated bonds in the chloropropene molecule and the large intermolecular force.

4. solubility
   Chloropropene is slightly soluble in water and easily soluble in organic solvents; chloropropane is almost insoluble in water and easily soluble in organic solvents. This difference is very important in the separation and purification process.

3. Chemical Properties Comparison

1. Flammability Chloropropene is flammable and can burn after ignition; chloropropane usually does not burn in air, but can be ignited with a high-energy ignition source.

2. chemical reaction activity Due to the presence of double bonds, chloropropene has high chemical reaction activity, which is prone to hydrogenation reduction reaction, polymerization reaction, etc.; chloropropane is completely saturated and has low chemical reaction activity, so it usually does not participate in complex chemical reactions.

3. Stability Chloropropene is easy to decompose under light or high temperature conditions, while chloropropane is relatively stable and has good high temperature resistance.

4. application field

1. Application of allyl chloride Chloropropene is widely used in the plastics industry, especially in the production of chloropropene thermoplastics and chloropropene copolymers. Chloropropene is also used in the manufacture of certain rubber materials.

2. Application of Chloropropane Chloropropane is mainly used in the manufacture of organic chlorine rubber, but also in the field of synthetic materials and plastic additives.

5. how to distinguish between chloropropene and chloropropane

Based on the above differences in properties, the following methods can be used to distinguish between chloropropene and chloropropane:

1. Physical Property Test By measuring physical properties such as density, melting point and boiling point, the category of the substance can be preliminarily judged.

2. Solubility test Allyl chloride is slightly soluble in water, while chloropropane is almost insoluble, and the two can be distinguished by solubility tests.

3. chemical reaction experiment Chloropropene is prone to hydrogenation reduction reaction, while chloropropane is inactive, which can be verified by chemical reaction experiments.

4. instrumental analysis Using instrumental analysis such as infrared spectroscopy (IR) or mass spectrometry (MS), the two can be more accurately distinguished.

6. summary

Although chloropropene and chloropropane differ only by one chlorine atom in molecular structure, their physical and chemical properties are significantly different. By comparing their molecular weight, density, melting point, solubility, chemical reactivity, etc., the two substances can be accurately distinguished. In practical applications, the selection of suitable substances needs to consider their performance characteristics and usage scenarios to ensure the safety and efficiency of the production process.