What happens when phenol is oxidized by na2cr2o7-h2so4

phenol in Na₂ Cr₂ O₂-H₂ SO₂ oxidation conditions

In the chemical industry, phenol (C≡H∞OH) is an important organic compound, which is often used to synthesize many chemicals because of its chemical activity. When phenol is oxidized, the oxidant often selected is chromium sulfate (Na₂ Cr₂ O₂-H₂ SO₂), under which conditions a typical acidic oxidation reaction occurs. In this paper, the oxidation reaction process, products and reaction mechanism of phenol under this condition will be analyzed in detail.

1. PHENOL CHEMICAL STRUCTURE AND OXIDATION CHARACTERISTICS

Phenol is a compound containing a benzene ring and a phenolic hydroxyl group. In its chemical structure, the phenolic hydroxyl group (-OH) is attached to the benzene ring. Because the benzene ring has a conjugated structure, the hydroxyl nitrogen atom in the phenolic hydroxyl group has a certain electron-donating ability, which makes phenol susceptible to oxidation under acidic conditions. The phenolic hydroxyl group of phenol has the activation effect of the ortho-para position, which makes the phenol show a certain selectivity in the oxidation reaction.

Under acidic conditions, sulfuric acid (H₂ SO₂) as a catalyst can enhance the acidic environment of the system and further activate phenol molecules. Under acidic conditions, sodium dichromate (Na Cr O₂) can be converted into strongly oxidizing dichromic acid (H₂ Cr O₂), thus becoming the main oxidant.

2. Phenol Oxidation Reaction Mechanism

In the acid chromium sulfate (Na₂ Cr₂ O₂-H₂ SO₂) system, the oxidation reaction of phenol is usually divided into the following steps:

1. Adsorption and activation: As a strong oxidant, dichromic acid (H₂ Cr₂ O₂) first interacts with the phenolic hydroxyl groups in the phenol molecule. The hydroxyl oxygen atom in the phenolic hydroxyl group has high electronegativity and is easily adsorbed by the oxidant.

2. Electron transfer: Under acidic conditions, Cr(VI) of dichromic acid is reduced to Cr(III), while the phenolic hydroxyl group in phenol is oxidized. The transfer of electrons causes the hydrogen atom in the phenolic hydroxyl group of phenol to be oxidized to a hydroxyl oxyanion (O.), which in turn is dehydrogenated to form o-benzoquinone.

3. Chain oxidation reaction: The resulting o-quinone is further oxidized to form a chain reaction. After the phenol hydroxyl group is oxidized, its conjugated structure is destroyed, which exposes more reaction sites, resulting in the formation of phthalic acid.

3. Phenol Oxidation Products and Structural Analysis

In the Na₂ Cr₂ O₂-H₂ SO₂ system, the oxidation product of phenol is mainly phthalic acid (phthalic acid), with the chemical formula C- H₂ (COOH). In its structure, two carboxylic acid groups (-COOH) are attached to two adjacent positions (ortho positions) of the benzene ring. Specifically, the oxidation reaction results in the phenolic hydroxyl group in phenol being oxidized to a carboxylic acid group, while the adjacent carbon atom is also oxidized.

Phthalic acid is an important organic compound with multiple carboxylic acid groups, which can be used to prepare polyester resins, polyamides and other polymer materials in subsequent reactions. Phthalic acid can also be used as a plasticizing agent, a flame retardant, etc.

4. Reaction Conditions on Oxidation Reaction

In the Na? Cr? O?-H? SO? in the system, changes in reaction conditions can significantly affect the oxidation reaction process of phenol and the generation of its products.

1. Effect of sulfuric acid concentration: The concentration of sulfuric acid directly affects the acidic strength of the reaction. Higher sulfuric acid concentration can enhance the acidity of the system, improve the activity of the oxidant, thereby accelerating the reaction rate. However, too high a sulfuric acid concentration may also lead to increased side reactions.

2. Effect of oxidant concentration: The concentration of Na₂ Cr₂ O₂ determines the supply of oxidant. Appropriate oxidant concentration can ensure the completeness of the reaction, but excess oxidant may lead to over-oxidation of the reaction to produce unnecessary by-products.

3. Effect of temperature: The reaction temperature has a significant effect on the rate of the oxidation reaction. A higher temperature may accelerate the reaction rate, but an excessively high temperature may cause side reactions or cause decomposition of phthalic acid.

5. Oxidation Reactions: Practical Applications and Prospects

The oxidation reaction of phenol under the condition of Na₂ Cr₂ O₂-H₂ SO₂ not only has important theoretical significance, but also has been widely used in industrial production. The synthesis of phthalic acid is one of the main application directions of the reaction, and its products can be used in plastics, rubber, coatings and other industries. The reaction can also be used for the deep oxidation of phenol to reduce the pollution of phenol to the environment.

6. conclusion

In the Na₂ Cr₂ O₂-H₂ SO₂ system, the oxidation of phenol is a multi-step chain reaction, and its product is mainly phthalic acid. The reaction process is significantly affected by the reaction conditions, including the concentration of the acid, the concentration of the oxidant, and the reaction temperature. Through the in-depth study of the reaction mechanism and products, the reaction conditions can be further optimized, the selectivity and yield of the products can be improved, and the development of related industrial applications can be promoted.

Through the above analysis, it can be seen that the oxidation reaction of phenol in acidic chromium sulfate system is an efficient and controllable chemical reaction, which has important industrial application value. An in-depth study of this reaction process will provide a more efficient and environmentally friendly production solution for the chemical industry.