Phenols - Reactions Of Phenols (Due To -Oh Group- Resemble To Alcohols)

Phenols: Reactions of Phenols (Due to -OH group - Resemble to Alcohols)

Phenols are aromatic compounds that contain a hydroxyl group (-OH) attached to a benzene ring.
The presence of the hydroxyl group gives phenols similar chemical properties to alcohols.
However, due to the aromaticity of the benzene ring, phenols exhibit unique reactivity.

Preparation of Phenols

From Haloarenes: Haloarenes can be treated with a strong base like NaOH to form phenols.
From Diazonium Salts: Aromatic primary amines (diazonium salts) can be converted to phenols by treating them with water or alcohol.
From Cumene: Cumene (isopropylbenzene) can be oxidized to produce phenol.

Acidic Nature of Phenols

Phenols are weak acids due to the presence of a hydroxyl group on the aromatic ring.
They can donate a proton (H+) from the hydroxyl group, making them stronger acids than alcohols.
The acidity of phenols can be attributed to the resonance stabilization of the phenoxide ion.

Phenols - Reaction with metals

Phenols react with metals, such as sodium or potassium, to form phenoxide salts.
These reactions are similar to the reactions of alcohols with metals.
Example: Reaction of phenol with sodium gives sodium phenoxide and hydrogen gas. C6H5OH + Na ⟶ C6H5ONa + H2

Reaction with Active Metals

Phenols react with active metals like sodium, potassium, or magnesium to form alkoxides.
The reaction involves the replacement of the hydrogen atom with the metal. C6H5OH + 2Na ⟶ C6H5ONa + H2

Esterification of Phenols

Phenols undergo esterification reactions similar to alcohols.
Phenols react with carboxylic acids or acid chlorides in the presence of an acid catalyst to form esters.
Example: Reaction of phenol with acetic acid in the presence of a mineral acid catalyst. C6H5OH + CH3COOH ⟶ C6H5OCOCH3 + H2O

Halogenation of Phenols

Phenols can undergo halogenation reactions in the presence of halogens like chlorine or bromine.
The presence of the -OH group activates the benzene ring towards electrophilic substitution reactions.
Example: Halogenation of phenol with bromine gives a mixture of 2,4,6-tribromophenol and 2,4,6-tribromophenoxide.

Nitration of Phenols

Phenols can undergo nitration reactions in the presence of a mixture of concentrated nitric acid and concentrated sulfuric acid.
The presence of the -OH group activates the benzene ring towards electrophilic substitution reactions.
Example: Nitration of phenol with concentrated nitric acid gives a mixture of 2-nitrophenol and 4-nitrophenol.

Reimer-Tiemann Reaction

The Reimer-Tiemann reaction is a method for introducing a formyl group (-CHO) into an aromatic ring.
Phenols react with chloroform (CHCl3) and a strong base, such as sodium hydroxide (NaOH), to form salicylaldehyde.
The reaction involves the formation of a carbene intermediate.

Kolbe-Schmidt Reaction

The Kolbe-Schmidt reaction converts phenols into salicylic acids.
Phenols are treated with carbon dioxide (CO2) and a strong base, such as sodium hydroxide (NaOH), to form salicylic acid.
The reaction involves the decarboxylation of an intermediate.

Bromination of Phenols

Phenols can undergo bromination reactions in the presence of bromine (Br2) and an acid catalyst.
The presence of the -OH group activates the benzene ring towards electrophilic substitution reactions.
Example: Bromination of phenol with bromine gives 2,4,6-tribromophenol as the major product.

Oxidation of Phenols

Phenols can be oxidized to form quinones or benzoquinones.
The oxidation can be carried out using oxidizing agents like alkaline potassium permanganate (KMnO4) or alkaline potassium dichromate (K2Cr2O7).
Example: Oxidation of phenol with alkaline potassium permanganate gives 1,4-benzoquinone.

Electrophilic Aromatic Substitution of Phenols

Phenols are more reactive than benzene towards electrophilic aromatic substitution reactions.
The presence of the -OH group activates the benzene ring and directs the incoming electrophile to the ortho and para positions.
Example: Nitration of phenol with nitric acid gives predominantly ortho and para nitrophenol.

Williamson Ether Synthesis

Phenols can undergo Williamson ether synthesis reactions to form ethers.
Phenols react with alkyl halides in the presence of a strong base, such as sodium hydride (NaH), to form ethers.
Example: Reaction of phenol with methyl iodide in the presence of sodium hydride gives methyl phenyl ether.

Fries Rearrangement

The Fries rearrangement is a reaction in which an aryl ester rearranges to form an ortho-substituted phenol.
It involves the migration of an acyl group from the carbonyl carbon to a neighboring carbon in the phenyl ring.
Example: Fries rearrangement of phenyl acetate gives ortho-hydroxyacetophenone.

Friedel-Crafts Acylation of Phenols

Phenols can undergo Friedel-Crafts acylation reactions to form acylated products.
The reaction involves the electrophilic substitution of a hydrogen atom in the phenol ring by an acyl group (-COR).
Example: Friedel-Crafts acylation of phenol with acetyl chloride gives ortho- and para-acetylphenol.

Kolbe-Schmitt Reaction

The Kolbe-Schmitt reaction converts phenols into salicylates.
Phenols are treated with carbon dioxide (CO2) and a strong base, such as sodium hydroxide (NaOH), to form salicylates.
Example: Kolbe-Schmitt reaction of phenol gives sodium salicylate.

Oxidative Coupling of Phenols

Phenols can undergo oxidative coupling reactions to form diaryl ethers.
The reaction involves the oxidative coupling of two phenol molecules using oxidizing agents like copper salts or peroxides.
Example: Oxidative coupling of phenol gives diphenyl ether.

RXN- Oxidation

Benzyl alcohol can be oxidized to benzoic acid using oxidizing agents like potassium permanganate (KMnO4) or potassium dichromate (K2Cr2O7).
The reaction involves the oxidation of the alcohol group to a carboxylic acid group.
Example: Oxidation of benzyl alcohol gives benzoic acid.

RXN- Reduction

Benzaldehyde can be reduced to benzyl alcohol using reducing agents like sodium borohydride (NaBH4) or lithium aluminum hydride (LiAlH4).
The reaction involves the reduction of the carbonyl group to a primary alcohol.
Example: Reduction of benzaldehyde gives benzyl alcohol.

Phenols - Reactions of phenols (Due to -OH group - Resemble to alcohols)

Phenols show similarities to alcohols in terms of reactivity due to the presence of the -OH group.
The hydroxyl group on the benzene ring makes phenols more acidic compared to alcohols.
Phenols can undergo various reactions such as:
- Formation of phenoxide salts with metals.
- Esterification to form esters.
- Halogenation reactions to introduce halogens.
- Nitration reactions to introduce nitro groups.
- Oxidation to form quinones or benzoquinones.

Phenols - Formation of Phenoxide Salts

Phenols can react with metals such as sodium or potassium to form phenoxide salts.
The reaction involves the deprotonation of the phenol by the metal, resulting in the formation of a phenoxide ion.
Example: Reaction of phenol with sodium gives sodium phenoxide and hydrogen gas.
- C6H5OH + Na ⟶ C6H5ONa + H2

Phenols - Esterification Reactions

Phenols can undergo esterification reactions similar to alcohols.
In the presence of an acid catalyst, such as sulfuric or hydrochloric acid, phenols react with carboxylic acids or acid chlorides to form esters.
Example: Reaction of phenol with acetic acid and sulfuric acid catalyst gives phenyl acetate and water.
- C6H5OH + CH3COOH ⟶ C6H5OCOCH3 + H2O

Phenols - Halogenation Reactions

Phenols can undergo halogenation reactions in the presence of halogens like chlorine or bromine.
The presence of the -OH group activates the benzene ring towards electrophilic substitution reactions.
Example: Halogenation of phenol with bromine gives a mixture of 2,4,6-tribromophenol and 2,4,6-tribromophenoxide.

Phenols - Nitration Reactions

Phenols can undergo nitration reactions in the presence of a mixture of concentrated nitric acid and concentrated sulfuric acid.
The presence of the -OH group activates the benzene ring towards electrophilic substitution reactions.
Example: Nitration of phenol with concentrated nitric acid gives a mixture of 2-nitrophenol and 4-nitrophenol.

Phenols - Oxidation Reactions

Phenols can be oxidized to form quinones or benzoquinones.
The oxidation can be carried out using oxidizing agents like alkaline potassium permanganate (KMnO4) or alkaline potassium dichromate (K2Cr2O7).
Example: Oxidation of phenol with alkaline potassium permanganate gives 1,4-benzoquinone.

Phenols - Electrophilic Aromatic Substitution

Phenols are more reactive than benzene towards electrophilic aromatic substitution reactions.
The presence of the -OH group activates the benzene ring and directs the incoming electrophile to the ortho and para positions.
Example: Nitration of phenol with nitric acid gives predominantly ortho and para nitrophenol.

Phenols - Williamson Ether Synthesis

Phenols can undergo Williamson ether synthesis reactions to form ethers.
Phenols react with alkyl halides in the presence of a strong base, such as sodium hydride (NaH), to form ethers.
Example: Reaction of phenol with methyl iodide in the presence of sodium hydride gives methyl phenyl ether.

Phenols - Fries Rearrangement

The Fries rearrangement is a reaction in which an aryl ester rearranges to form an ortho-substituted phenol.
It involves the migration of an acyl group from the carbonyl carbon to a neighboring carbon in the phenyl ring.
Example: Fries rearrangement of phenyl acetate gives ortho-hydroxyacetophenone.

Phenols - Friedel-Crafts Acylation

Phenols can undergo Friedel-Crafts acylation reactions to form acylated products.
The reaction involves the electrophilic substitution of a hydrogen atom in the phenol ring by an acyl group (-COR).
Example: Friedel-Crafts acylation of phenol with acetyl chloride gives ortho- and para-acetylphenol.