Synthesis Process of p-Bromoaniline

Basic Information:

Alias: 4-Bromoaniline, p-Bromoaniline

CAS No: 106-40-1

Molecular Formula: C6H6BrN

Molecular Weight: 172.02

Physical State:White to light yellow to light orange solid

Melting Point:56-62°C (lit.)

Boiling Point:230-250°C

Uses:Used in the manufacturing of azo dyes and organic synthesis

Employed in the preparation of dihydroquinazoline

4-Bromoaniline (4-Bromoaniline) is an important organic compound widely used in fields such as dyes, pharmaceuticals, and pesticides. Its main preparation method involves the reduction reaction of p-nitrobromobenzene. This article will provide a detailed introduction to the synthesis process of 4-Bromoaniline, including raw material preparation, reaction steps, post-treatment, and purification.

Raw Material Preparation

The primary raw material for 4-Bromoaniline is p-Bromonitrobenzene, and the reducing agents can include iron powder and hydrochloric acid, or hydrogen gas and a catalyst.

Raw Material List:

4-Bromoaniline

Iron powder (or hydrogen gas)

Hydrochloric acid (or another suitable reduction catalyst)

Ethanol or other organic solvents

Synthesis Process Steps

Reaction Preparation:

Dissolve p-Bromonitrobenzene in an appropriate amount of organic solvent, typically using ethanol or ether. This step should be conducted under stirring to ensure that the p-Bromonitrobenzene is fully dissolved.

Reduction Reaction:

Iron Powder and Hydrochloric Acid Reduction Method:

Gradually add iron powder to the p-bromonitrobenzene solution while slowly dripping in hydrochloric acid. Stir the reaction mixture at room temperature and gradually heat to reflux. The hydrogen gas produced during the reaction promotes the reduction of p-bromonitrobenzene, forming 4-Bromoaniline and water.

Hydrogen Reduction Method:

Introduce hydrogen gas into the p-bromonitrobenzene solution in the presence of a catalyst (such as palladium on carbon or a nickel catalyst) to carry out the reduction reaction. This reaction is typically performed under pressure and temperature-controlled conditions to ensure the efficient progress of the reduction.

Reaction Monitoring:

Monitor the reaction progress using thin-layer chromatography (TLC) or gas chromatography (GC) to ensure complete conversion of p-bromonitrobenzene to4-Bromoaniline. Once the reaction is complete, stop heating and cool the reaction mixture.

Post-Treatment:

After cooling the reaction mixture to room temperature, filter out the solid catalyst or iron powder residue. The filtrate contains 4-Bromoaniline  and other by-products. Wash the filtrate with water to remove hydrochloric acid and water-soluble impurities. Then use ethanol or ether to extract the organic layer, separating out the p-bromoaniline.

Purification:

The extracted organic layer is subjected to vacuum distillation or recrystallization to purify the 4-Bromoaniline. Recrystallization typically uses ethanol or another suitable organic solvent, and by controlling the temperature and solvent ratio, high-purity p-bromoaniline is obtained.

Safety Precautions

During the synthesis of 4-Bromoaniline, the following safety precautions must be observed:

Wear protective gloves and safety goggles during operation to avoid contact with skin and eyes.

Conduct the reaction in a well-ventilated environment to prevent the accumulation of toxic gases.

Follow relevant safety guidelines and operating procedures when handling and storing chemical reagents.

The synthesis process of 4-Bromoaniline  involves the reduction of p-bromonitrobenzene. By selecting appropriate reducing agents and reaction conditions, high-purity 4-Bromoaniline  can be efficiently prepared. This process has important applications in fields such as dyes, pharmaceuticals, and pesticides. Through strict control of reaction conditions and safe operation, the efficient and safe production of p-bromoaniline can be achieved.