PREPARATION OF PHENOLS

7activestudio

24 Jul 201402:25

Summary

TLDRThe 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.

Outlines

00:00

🔬 Phenol Preparation Methods

This paragraph discusses various methods of preparing phenol, starting with its isolation from coal tar. The text covers the treatment of chlorobenzene with sodium hydroxide at high temperature and pressure to form sodium phenoxide, which then converts to phenol upon acidification. It also mentions the conversion of benzene diazonium chloride to phenol by heating with water or dilute acids, and the treatment of benzene sulphonic acid with sodium hydroxide followed by acidification to produce phenol. Additionally, it explains the preparation of phenol from cumene hydroperoxide, obtained by oxidizing cumene. This method also yields acetone as a byproduct. Further, the paragraph covers the use of Grignard reagents and salicylic acid in phenol production. Finally, two methods involving the oxidation of benzene using H2O2 and vanadium pentoxide as catalysts are discussed.

Mindmap

Keywords

💡Phenol

Phenol, also known as carbolic acid, is an aromatic compound characterized by a hydroxyl group (-OH) bonded to a benzene ring. In the script, it is a central theme, discussed in relation to various production methods like from chlorobenzene, benzene diazonium chloride, and cumene. Phenol's relevance lies in its widespread use in the chemical industry, particularly in the production of plastics and pharmaceuticals.

💡Chlorobenzene

Chlorobenzene is an organic compound consisting of a chlorine atom attached to a benzene ring. It is used in the script as a starting material for phenol production when treated with sodium hydroxide (NaOH) under high temperature and pressure conditions. The compound undergoes a chemical transformation into sodium phenoxide, which upon acidification produces phenol.

💡Sodium Phenoxide

Sodium phenoxide is an intermediate compound formed when chlorobenzene or benzene sulphonic acid reacts with sodium hydroxide. It plays a crucial role in the phenol production process, as further treatment with acid leads to the formation of phenol. The formation of sodium phenoxide is a recurring step in various phenol synthesis pathways.

💡Diazonium Salts

Diazonium salts are a class of organic compounds that contain the functional group -N2+. In the script, benzene diazonium chloride is specifically mentioned as a precursor for phenol synthesis, where warming with water or treatment with dilute acids results in the formation of phenol. Diazonium salts are commonly used in organic chemistry for synthesizing aromatic compounds.

💡Cumene Process

The cumene process is an industrial method used for phenol production, involving the oxidation of cumene (isopropylbenzene) to form cumene hydroperoxide, which is then decomposed to yield phenol and acetone. This process is mentioned as the most common method of phenol production, with acetone being a significant byproduct in large quantities.

💡Sodium Hydroxide (NaOH)

Sodium hydroxide, also known as lye or caustic soda, is a strong base used in various chemical processes. In the context of the script, NaOH is involved in several phenol production methods, including reactions with chlorobenzene, benzene sulphonic acid, and diazonium salts. It facilitates the formation of sodium phenoxide, which is crucial for phenol synthesis.

💡Benzene Sulphonic Acid

Benzene sulphonic acid is a sulfonated derivative of benzene, where a sulphonic acid group (-SO3H) is attached to the benzene ring. In the video, it serves as a precursor to phenol production. When treated with sodium hydroxide, it forms sodium phenoxide, which upon acid treatment yields phenol. This reaction is one of the methods for synthesizing phenol.

💡Acetone

Acetone is a volatile, flammable liquid that serves as an important solvent and chemical in various industries. In the cumene process discussed in the script, acetone is a byproduct alongside phenol. Its large-scale production as a result of this process highlights its industrial significance, particularly in the manufacturing of plastics and pharmaceuticals.

💡Grignard Reagent

Grignard reagents are organomagnesium compounds (e.g., phenylmagnesium bromide) used in organic synthesis. In the script, the Grignard reagent is oxidized and hydrolyzed in the presence of acid to produce phenol. This method highlights the reagent's utility in forming carbon-carbon bonds and facilitating complex organic reactions.

💡Salicylic Acid

Salicylic acid is an organic compound known for its role in producing aspirin. In the script, its sodium salt is treated with soda lime to yield phenol. This process, known as decarboxylation, involves the removal of a carboxyl group from the molecule, emphasizing how various aromatic compounds can serve as precursors in phenol synthesis.

Highlights

Phenol or carbolic acid was first isolated from coal tar.

Chlorobenzene is treated with NaOH at 623 K and 320 atmospheric pressure to give sodium phenoxide.

Sodium phenoxide upon acidification gives phenol.

Benzene diazonium chloride, when warmed with water or treated with dilute acids, gives phenol.

Benzene sulphonic acid treated with NaOH gives sodium phenoxide, which on acid treatment gives phenol.

Cumene oxidation with air produces cumene hydroperoxide, which on treatment with dilute acid gives phenol and acetone.

The reaction of cumene hydroperoxide produces acetone in large quantities along with phenol.

Most phenol production is derived from cumene.

Phenyl magnesium bromide oxidation followed by hydrolysis in the presence of an acid yields phenol.

Sodium salt of salicylic acid, when treated with soda lime, gives phenol.

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

Benzene, when oxidized in the presence of V2O5 as a catalyst at 315°C, produces phenol.

The process of treating benzene diazonium chloride with water or acids produces phenol.

Phenol can also be synthesized from benzene via hydroxylation using H2O2 and V2O5 catalysts.

Greenat Reagent: Oxidation of phenyl magnesium bromide followed by acid hydrolysis results in phenol.