PREPARATION OF PHENOLS

Summary

The video explains various methods of preparing phenol, a crucial organic compound. It covers processes including treating chlorobenzene with NaOH, using benzene diazonium chloride, and methods involving benzene sulphonic acid, cumene, and Grignard reagents. The video also highlights the large-scale production of phenol from cumene, with acetone as a significant by-product. Additionally, it mentions oxidation and hydrolysis techniques involving benzene and salicylic acid to obtain phenol. The content is informative for those interested in organic chemistry and industrial phenol production.

Takeaways

• 🧪 Phenol, also known as carbolic acid, was first isolated from coal tar.
• 🧫 Chlorobenzene reacts with NaOH at 623 K and 320 atmospheric pressure to form sodium phenoxide, which gives phenol upon acidification.
• 💧 Benzene diazonium chloride, when warmed with water or treated with dilute acids, produces phenol.
• 🔬 Benzene sulphonic acid reacts with NaOH to form sodium phenoxide, which gives phenol upon acid treatment.
• 🍃 Cumene is oxidized to cumene hydroperoxide, which, when treated with dilute acid, yields phenol and acetone.
• 🧴 Acetone is a major byproduct in the industrial production of phenol via the cumene process.
• ⚗️ Grignard reagent (phenyl magnesium bromide) upon oxidation followed by hydrolysis in the presence of acid, forms phenol.
• 🌿 Sodium salicylate, when heated with soda lime, produces phenol.
• 🔥 Benzene reacts with H₂O₂ in the presence of HSO₃F to form phenol.
• 🔧 Benzene undergoes oxidation using V₂O₅ as a catalyst at 315°C to yield phenol.

Q & A

What is phenol and how was it first isolated?

Phenol, also known as carbolic acid, was first isolated from coal tar.

How is phenol prepared from chlorobenzene?

Chlorobenzene is treated with NaOH at 623 Kelvin and 320 atmospheric pressure to give sodium phenoxide, which upon acidification gives phenol.

How is phenol produced from diazonium salts?

Benzene diazonium chloride is warmed with water or treated with dilute acids to yield phenol.

How can phenol be prepared from benzene sulphonic acid?

Benzene sulphonic acid is treated with NaOH to produce sodium phenoxide, which upon acid treatment gives phenol.

What is the reaction mechanism for producing phenol from cumene?

Cumene is oxidized in air to form cumene hydroperoxide, which, when treated with dilute acid, yields phenol and acetone.

What by-product is obtained alongside phenol in the cumene process?

Acetone is obtained in large quantities as a by-product in the cumene process.

How is phenol produced from Grignard reagents?

Phenyl magnesium bromide is subjected to oxidation followed by hydrolysis in the presence of an acid to produce phenol.

How is phenol prepared from salicylic acid?

The sodium salt of salicylic acid is treated with soda lime, which gives phenol.

How can benzene be converted to phenol using H2O2?

Benzene reacts with H2O2 in the presence of HSO3F to yield phenol.

What catalyst is used to produce phenol from benzene via oxidation?

Vanadium pentoxide (V2O5) is used as a catalyst to oxidize benzene at 315°C to produce phenol.