4-Iodobenzene-1,2-Diamine

The main uses of 1,2-dibromoethane are: First, in the field of organic synthesis, it is an extremely important basic raw material. It can be used to prepare many bromine-containing compounds, such as the preparation of materials with flame retardant properties. 1,2-dibromoethane can be used as a starting reactant to participate in the reaction. Through a series of chemical reactions, bromine atoms are introduced into the material, thus giving the material excellent flame retardant properties. Second, in chemical production, it is often used as a solvent. Because of its suitable solubility, it can dissolve a variety of organic compounds. In some chemical processes that require a homogeneous reaction environment, 1,2-dibromoethane can fully contact the reactants, speed up the reaction process and improve the reaction efficiency. Third, in agriculture, it has been used as a soil fumigant. It can effectively kill pests, pathogens and harmful organisms such as weed seeds in the soil, ensure the healthy growth of crops, and increase crop yield. However, due to its potential harm to the environment and human health, its use has been subject to many restrictions.
"Tiangong Kaiwu" says: "1,2-dibromoethane has a wide range of uses. In organic synthesis, it is the basic material, which can make all kinds of bromine-containing materials and add flame retardant properties. In the field of chemical industry, it is often used as a solvent to make the reactants dissolve and touch, promote the speed of reaction, and increase the rate of yield. In the past, it was used in agriculture as a soil fumigation agent to remove insects, sterilize, kill grass seeds, and protect the growth of agricultural products to increase their yield. However, there are hidden dangers to the environment and people, and there are many restrictions on its use today. "

1,2-Dibromoethane is a colorless liquid and has the following physical properties:
First, the melting and boiling point characteristics. Its melting point is -35 ° C, and the boiling point is 131.4 ° C. This melting and boiling point makes 1,2-dibromoethane liquid at room temperature and pressure. A lower melting point means that at ambient temperatures slightly higher than -35 ° C, it melts from solid to liquid; and a boiling point of 131.4 ° C indicates that when heated to this temperature, 1,2-dibromoethane will change from liquid to gaseous, and a boiling phenomenon occurs.
Second, density characteristics. 1,2-dibromoethane is denser than water, about 2.18 g/cm ³. When mixed with water, there will be a stratification phenomenon. 1,2-dibromoethane is in the lower layer and water is in the upper layer. This characteristic is due to its large molecular structure and relative molecular weight, which makes the mass per unit volume greater than that of water.
Third, solubility. 1,2-dibromoethane is insoluble in water, but it can be miscible with organic solvents such as ethanol, ether, and chloroform. This is because 1,2-dibromoethane molecules are non-polar molecules. According to the principle of "similarity and miscibility", non-polar 1,2-dibromoethane has good miscibility with equally non-polar or weaker organic solvents, while water is a polar molecule, so 1,2-dibromoethane is insoluble in water. < Br > Fourth, appearance and smell. 1,2-dibromoethane is a colorless liquid when it is pure, but after being left for a long time, it often decomposes to produce a small amount of bromine and is slightly yellow, and has a chloroform-like odor.

1,2-dibromoethane is a colorless and transparent liquid with a special odor. It is slightly soluble in water and can be miscible with organic solvents such as alcohols, ethers, and chloroform. Its chemical properties are quite active, and it can participate in many chemical reactions, which is of great significance to organic synthesis.
From the perspective of substitution reaction, the bromine atom in the molecule of 1,2-dibromoethane is quite active and easily replaced by other atoms or groups. For example, in an aqueous solution of sodium hydroxide, a hydrolysis reaction can occur, and the bromine atom is replaced by a hydroxyl group to form ethylene glycol and sodium bromide. The principle of this reaction is that the negative hydroxyl ion has strong nucleophilicity and attacks the carbon atom, causing the bromine ion to leave. The reaction formula is as follows: $C_ {2} H_ {4} Br_ {2} + 2NaOH\ stackrel {H_ {2} O} {\ longrightarrow} C_ {2} H_ {4} (OH) _ {2} + 2NaBr $.
Talking about the elimination reaction, 1,2-dibromoethane in sodium hydroxide alcohol solution will undergo a elimination reaction to form acetylene, sodium bromide and water. During this process, the bromine atom and hydrogen atom on the adjacent carbon atom are removed under basic conditions to form an unsaturated carbon-carbon triple bond. The reaction mechanism is that the hydroxide ion in the alcohol solution captures the hydrogen atom, and the bromine ion leaves at the same time, which prompts the carbon-carbon bond rearrangement to form a triple bond. The reaction formula is: $C_ {2} H_ {4} Br_ {2} + 2NaOH\ stackrel {alcohol} {\ longrightarrow} C_ {2} H_ {2} ↑ + 2NaBr + 2H_ {2} O $.
1,2-dibromoethane can also react with some metal-organic reagents. For example, when reacted with magnesium in anhydrous ether, Grignard reagents can be formed. This Grignard reagent can be used to construct carbon-carbon bonds in organic synthesis, and can react with carbonyl compounds such as aldons and ketones to generate corresponding alcohols, which greatly enriches the synthesis path of organic compounds. The chemical properties of 1,2-dibromoethane are active, and it is like a delicate tool in the field of organic synthesis. With its many reaction characteristics such as substitution and elimination, it has laid the foundation for the preparation of many complex organic compounds and promoted the vigorous development of organic chemistry.

To prepare 1,2-dibromoethane, the synthesis method is to add ethylene and bromine. The reaction conditions are smooth, the product is single, and the yield is quite high.
Ethylene is prepared first, which can be obtained by dehydration of ethanol by concentrated sulfuric acid. Mix ethanol and concentrated sulfuric acid in a suitable ratio and heat it to about 170 ° C. The ethanol will be dehydrated to form ethylene. The chemical formula is: $C_ {2} H_ {5} OH\ xrightarrow [170 ^ {\ circ} C] {concentrated H_ {2} SO_ {4}} CH_ {2} = CH_ {2}\ uparrow + H_ {2} O $. The resulting ethylene gas is purified and removed to remove impurities, such as sulfur dioxide, which may affect the subsequent reaction.
Then pure ethylene is introduced into bromine water or bromine carbon tetrachloride solution. Ethylene has a carbon-carbon double bond, which is chemically active and can undergo an addition reaction with bromine. The bromine-bromine bond is broken in the bromine molecule, and two bromine atoms are added to the carbon atoms at both ends of the ethylene double bond to form 1,2-dibromoethane. The reaction formula is: $CH_ {2} = CH_ {2} + Br_ {2}\ longrightarrow CH_ {2} BrCH_ {2} Br $. In this process, the reddish-brown color of bromine water or bromine tetrachloride solution gradually fades, which is a sign of the reaction.
There are other methods to produce 1,2-dibromoethane, but the method of ethylene and bromine addition is the most commonly used. Because of its easy availability of raw materials, simple reaction steps, and easy separation and purification of the product. And this reaction has high atomic utilization, which is in line with the concept of green chemistry, and is of great value in industrial production and laboratory preparation.

When storing and transporting 1,2-dibromoethane, many matters need to be paid attention to.
First, it concerns packaging. 1,2-dibromoethane is toxic and corrosive, so the packaging must be strong and tight to prevent leakage. Commonly used packaging materials include glass bottles, metal barrels, etc. However, glass bottles need to be protected from damage. Metal barrels should be made to ensure that the material is resistant to corrosion and well sealed. If they are packed in metal barrels, check the barrel body for rust, holes, etc. If so, it is easy to leak, endangering the surrounding environment and personal safety.
Second, the control of temperature and humidity is crucial. This substance is more sensitive to temperature and humidity. High temperature can easily cause its volatilization to intensify, and even cause the pressure in the container to rise, which may cause explosion; if the humidity is too high, it may cause chemical reactions such as hydrolysis to occur, which will affect the quality. Therefore, it should be stored in a cool and dry place. The warehouse temperature should be maintained within a certain range, such as 15 ° C - 25 ° C, and the humidity should be controlled at 40% - 60%.
Third, avoid mixing with other substances. 1,2-dibromoethane can react with many substances, such as strong oxidants, strong bases, etc. If mixed with it, once it comes into contact, it may cause severe chemical reactions, such as combustion, explosion and other serious consequences. Therefore, it is necessary to store and transport it separately, and keep a safe distance from other contraindications.
Fourth, during transportation, the means of transportation need to take protective measures. Vehicles should be equipped with corresponding leakage emergency treatment equipment, such as adsorption materials, protective gear, etc. During driving, it is necessary to drive smoothly to avoid bumps and collisions to prevent leakage caused by packaging damage. When loading and unloading, operators should also be careful, follow the operating procedures, and unload lightly.