How to prepare aniline from phenol

How to prepare aniline

In organic chemistry, the conversion of phenol to aniline involves the conversion of a hydroxyl group (-OH) to an amino group (-NH₂). This process can be achieved by the following steps:

1. Acidic conditions of hydroxyl activation

Phenol reacts under acidic conditions, usually with concentrated sulfuric acid (H₂ SO₂), to produce phenyl sulfate. This conversion increases the ability of the hydroxyl group to leave, making it easier to participate in subsequent reduction reactions. The reaction is as follows: [\text{C}6\text{H}5\text{OH} \text{H}2\text{SO}4 \rightarrow \text{C}6\text{H}5\text{OSO}3\text{H} \text{H}2\text{O}]

2. Reduction reaction

Phenyl sulfate was placed in dilute hydrochloric acid (HCl), and iron powder (Fe) was added, and a reduction reaction was carried out under a heated condition. Iron acts as both a catalyst and a reducing agent, reducing adjacent groups to amino groups. The reaction process is as follows: [ \text{C}6\text{H}5\text{OSO}3\text{H} \xrightarrow{\text{Fe/HCl}} \text{C}6\text{H}5\text{NH}2 \text {other products}]

3. Specific operation steps

• Prepare materials: phenol, concentrated sulfuric acid, dilute hydrochloric acid, iron powder.
• The first step: the phenol and concentrated sulfuric acid mixing, heating reflux, generate phenyl sulfate.
• Second step: The phenyl sulfate solution is transferred to dilute hydrochloric acid, iron powder is added, and heating is continued until the reaction is completed.
• Third step: by distillation or filtration to extract the aniline.

4. Reaction mechanism

Iron powder provides H and electrons in dilute hydrochloric acid, reducing adjacent groups in phenylsulfates. The hydroxyl group on the benzene ring is activated under acidic conditions, which is convenient for Fe atom to attack and generate aniline. The reaction is a typical reduction reaction under acidic conditions, with mild conditions and simple operation.

5. Applications and Advantages

Aniline is an important chemical, widely used in dyes, drugs and pesticides and other fields. The method of preparing aniline from phenol has the advantages of simple steps, mild conditions and low cost, and is especially suitable for industrial production.

In summary, phenol can be efficiently converted to aniline by hydroxyl activation and iron powder reduction under acidic conditions. This method is not only practical, but also provides an important reference for subsequent organic synthesis.